Dissertations / Theses on the topic 'Crop and Pasture Production'

This research examined the mechanisms by which temperature, water availability and nitrogen (N) affect the dry matter (DM) yield potential of cocksfoot (Dactylis glomerata L.) dominant pastures. The experiment was a split plot design with main plots of fully irrigated (I) or dryland (D), sub-plots of N fertiliser at 800 kg N/ha in 2003/04; and 1600 kg N/ha in 2004/05 (+N) or 0 kg N/ha (-N). The potential environmental yield of an established 8 year old cocksfoot dominant pasture was 21.9 t DM/ha/y from I+N pastures compared with 9.8 t DM/ha by I-N pastures and 15.1 t DM/ha/y by D+N pastures. The lowest yields were from dryland pastures with no N which produced 7.5 t DM/ha/y in 2003/03 and 5.0 t DM/ha/y in 2004/05. The effect of seasonal temperatures on the DM production, when periods of water stress were excluded, was quantified using thermal time accumulated above a base temperature of 3°C as 7.0 kg DM/°Cd/ha for N fertilised pastures and 3.3 kg DM/°Cd/ha for pastures with no N. The 2.5 t DM/ha difference in yields of D-N pastures in 2003/04 and 2004/05 was the result of the duration, extent and timing of the water stress period. In both years the critical limiting deficit (DL) was calculated as 78 mm from the soil moisture deficit in the 0-0.8 m soil layers. Beyond DL yield decreased at a rate of 1.45%/mm in +N and –N pastures, relative to fully irrigated control pastures. Yields of D+N and D-N pastures were similar during periods of water stress with 0.4±0.1 t/DM/ha produced during the rotation ending 30/12/2003. This was less than from either the I-N (1.2 t DM/ha) or I+N (3.5 t DM/ha) pastures due to the reduction in the amount of photosynthetically active radiation intercepted by the canopies of the dryland pastures. However, in the rotation ending 2/5/2004, after autumn rain alleviated drought conditions, yield of the D+N pasture was 2.1 t DM/ha compared with 1.7 t DM/ha by I+N pastures. The effect of N on yield was described using a nutrition index which showed that as DM yield increased N% in the herbage declined. This is a function of the ratio between metabolic and structural N requirements rather than caused by ontogeny alone. Specific leaf N was determined at two harvests and appeared constant at a given point in time (1.0-1.6 g N/m² leaf). In contrast, specific pseudostem N increased from 0.8-1.0 g N/m² pseudostem at an NNI of 0.4 in –N pastures to 2.6-3.0 g N/m² pseudostem at an NNI of 1.2 in the +N pastures. Differences between the yields of +N and –N pastures were caused by differences in radiation use efficiency (RUE) as determined by the linear relationship (R²=0.76) between RUE and the nitrogen nutrition index (NNI). In this thesis, empirical relationships for the effects of temperature, water availability and N were derived and the physiological mechanisms which underlie these descriptions were identified. These relationships provide clear and simple explanations of the effects of environmental variables on the productivity of cocksfoot based pastures which will enhance understanding of the benefits and limitations of cocksfoot, particularly in dryland farming systems.

The general goal of this research was to understand the agronomic and physiological changes of a lucerne crop in distinct physical radiation environments and to verify the potential of lucerne to grow under shaded conditions. To achieve this, the research was conducted in four main steps: (i) firstly, experimental data collection in the field using two artificial shade materials (shade cloth and wooden slats) under inigated and non-irrigated conditions; (ii) a second experiment with data collection in a typical temperate dryland agroforestry area under non-irrigated conditions; (iii) generation of a light interception sub-model suitable for shaded crops and (iv) a linkage between the light interception sub-model and a canopy photosynthesis model for agroforestry use. In experiments 1 and 2, lucerne crop was exposed to 6 different light regimes: full sunlight (FS), shade cloth (FS+CL), wooden slats (FS+SL), trees (T), trees+cloth (T +CL) and trees+slats (T+SL). The FS+SL structure produced a physical radiation environment (radiation transmission, radiation periodicity and spectral composition) that was similar to that observed in the agroforestry site (f). The mean annual photosynthetic photon flux density (PPFD) was 41 % under the FS+CL, 44% under FS+SL and 48% under T compared with FS in clear sky conditions. Plants were exposed to an intermittent (sun/shade) regime under both FS+SL and T, whereas under FS+CL the shaded light regime was continuous. The red to far-red (RIFR) ratio measured during the shade period under the slats was 0.74 and under the trees was 0.64. However, R/FR ratio increased to 1.26 and 1.23 during the illuminated period under FS+SL and T, respectively, and these were equivalent to the ratio of 1.28 observed under the FS+CL and 1.31 in FS. The radiation use efficiency (RUE) of shoots increased under the 5 shaded treatments compared with full sunlight. The pattern of radiation interception was unchanged by radiation flux, periodicity and spectral composition and all treatments had a mean extinction coefficient of 0.82. However, the magnitude of the decrease in canopy growth was less than those in PPFD transmissivity. The mean lucerne annual dry matter (DM) yield was 17.5 t ha⁻¹ in FS and 10 t ha⁻¹ under the FS+CL, FS+SL and T regimes. This declined to 3.4 t DM ha⁻¹ under T+CL (22% PPFD transmissvity) and 4.1 t DM ha⁻¹ under T+SL (23% transmissivity). A similar pattern of response was observed for leaf net photosynthesis (Pn) rates under the shade treatments compared with full sun. In addition, spectral changes observed under the trees and slats affected plant motphology by increasing the number of long stems, stem height and internode length compared with full sunlight. Thus, there were two main explanations for the increase in RUE under shade compared with full sun: (i) preferential partition of assimilates to shoot rather than root growth and/or (ii) leaves under shade were still operating at an efficient part of the photosynthetic light curve. The changes proposed for the canopy Pn model were appropriate to simulate the radiation environment of an agroforestry system. However, the model underestimated DM yields under the continuous and intermittent shade regimes. These were considered to be mainly associated with plant factors, such as overestimation in maintenance respiration and partitioning between shoots and roots in shade and the intermittency light effect on leaf Pn rates. Further investigation in these topics must be addressed to accurately predict crop yield in agroforestry areas. Overall, the lucerne crop responded typically as a sun-adapted plant under shade. It was concluded that lucerne yield potential to grow under intermediate shade was superior to most of C3 pastures previously promoted in the literature.

The annual and seasonal water use efficiency of six pasture combinations were calculated from the ‘MaxClover’ Grazing Experiment at Lincoln University. Pastures have been established for six years and are grazed by best management practices for each combination. Measurements for this study are from individual plots of four replicates of ryegrass (RG)/white clover (Wc), cocksfoot (CF)/Wc; CF/balansa (Bal) clover; CF/Caucasian (Cc) clover; CF/subterranean (Sub) clover or lucerne. Water extraction measurements showed soils for all dryland pastures had a similar plant available water content of 280±19.8 mm. Dry matter measurements of yield, botanical composition and herbage quality were assessed from 1 July 2008 until 30 June 2009. Lucerne had the highest annual yield of 14260 kg DM/ha/y followed by the CF/Sub at 9390 kg DM/ha/y and the other grass based pastures at ≤ 6900 kg DM/ha/y. All pastures used about 670±24.4 mm/y of water for growth. Lucerne had the highest annual water use efficiency (WUE) of 21 kg DM/ha/mm/y of water used (total yield/total WU). The WUE of CF/Sub was the second highest at 15 kg DM/ha/mm/y, and the lowest was CF/Wc at 9 kg DM/ha/mm/y. The CF/Sub pastures had the highest total legume content of all grass based pastures at 21% and as a consequence had the highest annual nitrogen yield of 190 kg N/ha. This was lower than the monoculture of lucerne (470 kg N/ha). Ryegrass/white clover had the highest total weed component in all pastures of 61%. For dryland farmers spring is vital for animal production when soil temperatures are rising and moisture levels are high. The water use efficiency at this time is important to maximize pasture production. In spring lucerne produced 8730 kg DM/ha, which was the highest dry matter yield of all pastures. The CF/Sub produced the second highest yield of 6100 kg/DM/ha. When calculated against thermal time, CF/Sub grew 5.9 kg DM/ºCd compared with lucerne at 4.9 kg DM/ºCd. The higher DM yield from lucerne was from an extra 400 ºCd of growth. The highest seasonal WUE of all pastures occurred in the spring growing period. Linear regressions forced through the origin, showed lucerne (1/7/08-4/12/08) had a WUE of 30 kg DM/ha/mm (R2=0.98). Of the grass based pastures, CF/Sub produced 18 kg DM/ha/mm (R2=0.98) from 1/7 to 10/11/08 from 270 mm of water used. The lowest spring WUE was 13.5 kg DM/ha/mm by CF/Bal pastures which was comparable to the 14.3±1.42 kg DM/ha/mm WUE of CF/Wc, CF/Cc and RG/Wc pastures. During the spring, CF/Sub clover had the highest spring legume component of the grass based pastures at 42% and produced 120 kg N/ha. This was lower than the 288 kg N/ha from the monoculture of lucerne. Sub clover was the most successful clover which persisted with the cocksfoot. Based on the results from this study dryland farmers should be encouraged to maximize the potential of lucerne on farm, use cocksfoot as the main grass species for persistence, rather than perennial ryegrass, and use subterranean clover as the main legume species in cocksfoot based pastures. By increasing the proportion of legume grown the water use efficiency of a pasture can be improved. When pastures are nitrogen deficient the use of inorganic nitrogen may also improve pasture yields particularly in spring.

Variables for the accelerated ageing (AA) test, methods for reducing fungal contamination during the AA test, using the conductivity test as a vigour test, the effect of seed size on seed vigour and the relationship between laboratory test results and field perfonnance in selected Brassica spp were investigated. In the first experiment, three seed lots of turnip rape hybrid (B. rapa x campestris), turnip (B. campestris) and forage rape (B. napus); and seven seed lots of Asian rape (B. napus), six seed lots of Asian kale (B. oleraceae var. alboglabra L.) and five seed lots of choisum (B. rapa var. pekinensis) with germinations above 90% were aged at two different temperatures (41 and 42°C ± 0.3°C) and three ageing times (24, 48 and 72 ± 15 minutes). The second experiment was divided into three sections. In the first, the same seed lots and species were aged at one temperature (41°C) and time (72 h), but either 40 ml of saturated salts; KCl (83%RH), NaCl (76%RH), NaBr (55%RH); or distilled water (96%RH) were used as the ageing solutions. In the second, one turnip rape hyprid seed lot was aged at three temperatures (41, 42 and 45°C) and two times (72 and 96h), again using the three saturated salts and distilled water as ageing solutions. In the third, three turnip rape hybrid seed lots and three Asian kale seed lots were surface sterilised (1 % sodium hypochlorite) prior to ageing at one temperature (41°C) and time (72 h). In the third experiment, the same species and seed lots used in experiment one at their original seed moisture content (SMC) were tested for conductivity after soaking in deionised water for 4, 8, 12, 16, 20 and 24 h. They were then re-tested after the SMC had been adjusted to 8.5%. In the fourth experiment, three seed lots of forage rape and three seed lots of Asian kale were graded into three seed size categories; large (retained on a 2.0 mm screen), medium (retained on a 1.7 mm screen) and small (passed through a 1.7 mm screen). Graded seeds were then tested for standard germination, AA (41°C/48 h) and conductivity (measured at 16 and 24 h). In the final experiment, the relationships between laboratory tests for the six species (each consisting of three seed lots), field emergence from three sowings, and cold room emergence were evaluated. Both time and temperature influenced post-AA germination. Increasing the ageing period from 48 to 72 hours at 41°C, and 24 to 48 hours at 42°C resulted in decreased mean germination percentage for all species but not always clear separation of seed lots. While there were sometimes few differences between ageing at 41°C and 42°C, the former is preferred because it is already the temperature used for other species. For Asian rape, choisum and turnip, the previously recommended testing conditions of 41°C/72 h provided good seed lot separation, but for Asian kale and turnip rape hybrid, AA testing at 41°C/48 h provided better results. Seed moisture content after ageing ranged from 29-37% depending on species. Fungal growth on seeds during the ageing period appeared to reduce post-ageing germination in some seed lots . Substituting saturated salts for distilled water did not stress seed lots in the AA test, due to the lowered RH%, the exception being seed lots 1210 and 1296. For forage and Asian species, seed lot germination mostly remained above 90% when aged for 72 h at lowered RH%. Increasing the ageing duration from 72 to 96 hours resulted in some decreases in post-AA germination but no clear separation of seed lots. Surface sterilising the seeds prior to the AA test resulted in a lower incidence of contaminant fungi which was associated with a lower percentage of abnormal seedlings. The conductivity test was mostly able to identify vigour differences among forage and Asian vegetable brassica seed lots. Differences in conductivity readings were observed among seed lots in all species. Increasing the period of imbibition resulted in increased conductivity from most seed lots but radicle emergence occurred after 16-20 h of imbibition. Variation was observed in the time to reach 95% maximum of the imbibition curve for most species. Conductivity readings at 16 h would avoid possible influences of radicle emergence on results. Adjusting the SMC to 8.5% resulted in reduced variation in conductivity among replicates of seed lots, due to a reduction in imbibition damage. Seed size had a significant effect on both post-AA germination and conductivity results. In forage rape, large size seeds had higher post-AA germination cf. medium cf. small size seeds. In Asian kale, large size seeds had higher post-AA germination compared with small size seeds. For both forage rape and Asian kale, large size seeds had lower conductivity readings cf. small size seeds. The correlation analyses demonstrated significant relationships between AA testing and field emergence parameters (percentage emergence, emergence index and emergence rate). Significant relationships were also observed between conductivity testing and these field emergence parameters. Based on the correlation analysis, AA testing at 41°C/48 hand/or 42°C/48 h could be recommended to be used as an AA test for turnip and Asian rape; and 41°C/48 hand/or 41°C/72 h for Asian kale and choisum. Based on the correlation analysis, conductivity testing at 16 h can be used to predict the field emergence potential of forage and Asian vegetable seed lots. Vigour tests were consistently able to provide better indicators of field perfonnance than the standard germination test, although these relationships did vary with the different field sowings.

Bumble bees (Bombus spp.: Apidae) are valuable pollinators of many crop and wildflower species. However, in some situations their potential is limited. Evaluation of, and management to improve bumble bee efficacy should include spatial information which is currently limited. Distance and direction determine the success of gene flow via pollen cross-over within and between plant populations at several scales. Studies of movement by bumble bees at large scales in semi-natural and intensively managed habitats are scarce. Few studies of bumble bee dispersal from the nest exist, particularly in relation to crops. At a small scale, directional rather than random movement between flowers has benefits for pollen flow. Results to date of directionality studies at small scales and their interpretation are inconsistent. The purpose of this thesis was to assess distances and directions moved by foraging bumble bees at a range of scales in two contrasting farm habitats in order to predict their pollination potential. A novel method was developed to mark automatically all the occupants of nests of bumble bees B. terrestris (L.) placed around a Lucerne seed crop Medicago sativa L. in New Zealand. Reobservation data from eight nests showed that of bumble bees which foraged within the crop, 81 % travelled ≤ 50 m and 56% ≤ 20 m from their nest. Results should be interpreted with extreme caution because fewer than 1 % of bumble bees marked at nests were reobserved in the crop. Because it was not established where the other 99% of the bumble bees went, foraging areas for nests could not be calculated as anticipated. Theories to explain the non-specificity of bumble bees to the crop include; resource depletion near nests, competition with honey bees in the crop, or an evolved strategy to disperse in order to minimise nest predation. Lucerne flowers contained a significantly lower concentration of sugar in nectar, and significantly fewer pollen grains than did those of purple loosestrife Lythrum salicaria L., a species on which bumble bees appeared to forage in preference Lucerne. The higher rewards offered by L. salicaria may have diverted bumble bees from the less-rewarding Lucerne crop. In a Norwegian meadow system, all foraging bouts by bumble bees B. lucorum (L.) within a patch of wood cranesbill flowers Geranium sylvaticum L. were random with respect to direction. This result is not consistent with predictions, based on optimal foraging theory, that movement should be directional to enable optimal pollen flow, and to avoid revisitation of just-emptied flowers by the pollinator. A medium-scale study of several bumble bee species moving between patches of northern wolfsbane Aconitum septentrionale Koelle in Norway revealed considerable loyalty by bumble bees to patches in which they were marked. In a different landscape-scale study (over 5 ha), several bumble bees exhibited a high degree of loyalty to areas in which they were marked (87% were reobserved ≤ 50 m from marking points). These restricted movement patterns are discussed in terms of potential pollen flow. Of 260 bumble bees marked, only five were recorded crossing between meadows, which could be a result of innate loyalty to small forage areas, an artefact of the sampling technique used, or forest boundaries acting as physical impediments to movement. In the future, spatial data of the type collected in this thesis will aid in the management of bumble bee populations to achieve both commercial and conservation goals. Spatial data can be applied to predict the optimal placement of artificially-reared nests, predict suitable isolation distances for pure seed crops, and aid in the positioning of supplementary forage sources and nest-site refuges.

The association between individual plant performance and seed yield variability within and between field pea crops was investigated. In 1988/89 six F8 genotypes with morphologically distinct characteristics were selected from a yield evaluation trial. Analysis of the individual plant performance within these crops indicated an association between low seed yields and the location and dispersion of plant harvest index (PHI) and plant weight (PWT) distributions. The analyses also showed there was a strong linear relationship between the seed weight (SWT) and PWT of the individual plants within each crop, and that the smallest plants tended to have the lowest PHI values. A series of 20 simulations was used to formalize the relationships between SWT, PWT and PHI values within a crop into a principal axis model (PAM). The PAM was based on a principal axis which represented the linear relationship between SWT and PWT, and an ellipse which represented the scatter of data points around this line. When the principal axis passed through the origin, the PHI of a plant was independent of its PWT and the mean PHI was equal to the gradient of the axis. However, when the principal axis had a negative intercept then the PHI was dependent on PWT and a MPW was calculated. In 1989/90 four genotypes were sown at five plant populations, ranging from 9 to 400 plants m⁻². Significant seed and biological yield differences were detected among genotypes at 225 and 400 plants m⁻². The plasticity of yield components was highlighted, with significant genotype by environment interactions detected for each yield component. No relationship was found between results for yield components from spaced plants and those found at higher plant populations. The two highest yielding genotypes (CLU and SLU) showed either greater stability or higher genotypic means for PHI than genotypes CVN and SVU. Despite significant skewness and kurtosis in the SWT, PWT, and PHI distributions from the crops in this experiment, the assumptions of the PAM held. The lower seed yield and increased variability in PHI values for genotype CVN were explained by its higher MPW and the positioning of the ellipse closer to the PWT axis intercept than in other genotypes. For genotype SVU, the lower seed yield and mean PHI values were explained by a lower slope for the principal axis. Both low yielding genotypes were originally classified as having vigorous seedling growth and this characteristic may be detrimental to crop yields. A method for selection of field pea genotypes based on the PAM is proposed. This method enables the identification of weak competitors as single plants, which may have an advantage over vigorous plants when grown in a crop situation.

The contamination of process pea (Pisum sativum L.) crops by the immature fruit of black nightshade (Solanum nigrum L.) and hairy nightshade (S. physalifolium Rusby var. nitidibaccatum (Bitter.) Edmonds) causes income losses to pea farmers in Canterbury, New Zealand. This thesis investigates the questions of whether seed dormancy, germination requirements, plant growth, reproductive phenology, or fruit growth of either nightshade species reveal specific management practices that could reduce the contamination of process peas by the fruit of these two weeds. The seed dormancy status of these weeds indicated that both species are capable of germinating to high levels (> 90%) throughout the pea sowing season when tested at an optimum germination temperature of 20/30 °C (16/8 h). However, light was required at this temperature regime to obtain maximum germination of S. nigrum. The levels of germination in the dark at 20/30 °C and at 5/20 °C, and in light at 5/20 °C, and day to 50 % germination analyses indicated that this species cycled from nondormancy to conditional dormancy throughout the period of investigation (July to December 2002). For S. physalifolium, light was not a germination requirement, and dormancy inhibited germination at 5/20 °C early in the pea sowing season (July and August). However, by October, 100% of the population was non-dormant at this test temperature. Two field trials showed that dark cultivation did not reduce the germination of either species. Growth trials with S. nigrum and S. physalifolium indicated that S. physalifolium, in a non-competitive environment, accumulated dry matter at a faster rate than S. nigrum. However, when the two species were grown with peas there was no difference in dry matter accumulation. Investigation of the flowering phenology and fruit growth of both species showed that S. physalifolium flowered (509 °Cd, base temperature (Tb) 6 °C) approximately 120 °Cd prior to S. nigrum (633 °Cd). The fruit growth rate of S. nigrum (0.62 mm/d) was significantly faster than the growth rate of S. physalifolium (0.36 mm/d). Because of the earlier flowering of S. physalifolium it was estimated that for seedlings of both species emerging on the same date that S. physalifolium could produce a fruit with a maximum diameter of 3 mm ~ 60 °Cd before S. nigrum. Overlaps in flowering between peas and nightshade were examined in four pea cultivars, of varying time to maturity, sown on six dates. Solanum physalifolium had the potential to contaminate more pea crops than S. nigrum. In particular, late sown peas were more prone to nightshade contamination, especially late sowings using mid to long duration pea cultivars (777-839 °Cd, Tb 4.5 °C). This comparison was supported by factory data, which indicated that contamination of crops sown in October and November was more common than in crops sown in August and September. Also, cultivars sown in the later two months had an ~ 100 °Cd greater maturity value than cultivars sown in August and September. Nightshade flowering and pea maturity comparisons indicated that the use of the thermal time values for the flowering of S. nigrum and S. physalifolium can be used to calculate the necessary weed free period required from pea sowing in order to prevent the flowering of these species. The earlier flowering of S. physalifolium indicates that this species is more likely to contaminate pea crops than is S. nigrum. Therefore, extra attention may be required where this species is present in process pea crops. The prevention of the flowering of both species, by the maintenance of the appropriate weed free period following pea sowing or crop emergence, was identified as potentially, the most useful means of reducing nightshade contamination in peas.

The vegetative and reproductive development of balansa clover (Trifolium michelianum Savi.) were quantified in relation to the environmental drivers of each phenophase in field and controlled environments. In a grazed experiment over 6 years, balansa clover sown with cocksfoot (Dactylis glomerata) contributed 1.6 t DM/ha/year, or ~20% of the total DM production. However, grazing management for increased seed production during flowering in the establishment year strongly influenced balansa clover regeneration. The earliest closed plot (September) averaged between 2.2 and 4.3 t DM/ha/year of balansa clover across all six years. In an incubator, balansa clover required 29°Cd for germination with an optimum temperature of 14°C and a maximum of 40°C. The base temperature for germination was 0°C. A field experiment determined that 38°Cd were required for emergence with an optimum soil temperature (Topt) of 8.5°C. The time from emergence until the first leaf appeared, the phyllochron and timing of axillary leaf appearance were compared with perennial ryegrass (Lolium perenne) and white clover (Trifolium repens L.). The rate of each was found to increase linearly with temperature. The balansa clover cultivar ‘Frontier’ required 97°Cd from sowing for the first leaf to appear, had a phyllochron of 47°Cd and secondary leaves appeared after 490°Cd. For each vegetative stage, the base temperature was 2.5°C. The timing of flower appearance depended on the quantity and direction of change of the photoperiod at emergence. A balansa clover plant, cv. ‘Bolta’, which emerged on 1 December into an increasing photoperiod of 15.6 hours flowered after 574°Cd (Tbase = 2.5°Cd) or 58 days after emergence. In contrast, if the plant emerged on 16 January into a similar but decreasing photoperiod it took 1503°Cd or 227 days to flower. This length of time became progressively shorter until remaining constant after the shortest day. In contrast, ‘Frontier’ took a constant 390 and 690 °Cd in increasing and decreasing photoperiods, respectively. The time which an individual inflorescence took from pollination until seeds were physiologically mature was 250 °Cd for both ‘Bolta’ and ‘Frontier’. The re-establishment of balansa clover each year relied on a large seed set (>1000 kg/ha) in the establishment year. The continued survival of balansa clover would then depend on a similar seeding event within a 4-5 year period to maintain the seed bank. Management considerations for balansa clover persistence and survival are discussed.

Leafy vegetables, lettuce (Lactuca sativa L. cv. Green Oakleaf), pak choi (Brassica sinensis L. cv. Oriental Taisai) and rocket (Eruca sativa L.), were planted in an open field at Lincoln University on January 2005. Plants were harvested at 5 cm cutting height above the growing point with three different harvest start times, early start (ES), mid start (MS) and late start (LS) of harvest respectively. There were three harvests during the growing season with a 4-week interval between harvests. Generally, lettuce produced significantly higher total FW/plant (208 g) than pak choi or rocket (123 and 102 g total FW/plant, respectively). Lettuce also produced significantly higher total FW/plant than pak choi or rocket in each treatment. Lettuce produced significantly more total saleable leaf FW/plant in the ES, MS and LS treatment (137.5, 120.9 and 169.3 g FW/plant), compared with pak choi (52.9, 100 and 92 g FW/plant) or rocket (31.5, 92.2 and 56.4 g FW/plant). Pak choi produced higher total saleable leaf FW/plant than rocket in the ES and LS treatments, but a similar total saleable leaf FW/plant in the MS treatment. The best time to start harvesting was the LS treatment for lettuce, while pak choi and rocket produced better yields in the MS and LS treatments. Results for total DW/plant showed that different harvest start times did not affect the total DW/plant in lettuce. However, pak choi and rocket produced less total DW/plant in the ES treatment compared to the MS or LS treatments. This was due to a faster recovery by lettuce. In addition, lettuce produced significantly higher DW/plant during regrowth at the second and third harvests than pak choi or rocket, even though it was significantly lower at the first harvest. It is likely that after harvesting greater carbohydrate reserves and greater remaining leaf area produced greater regrowth potential in lettuce. These results suggest that lettuce has the most regrowth potential, while rocket has more than pak choi in this reaping and regrowth system. When plants were harvested at the same cutting level, lettuce had the most remaining leaf area of the three species. This remaining leaf area for lettuce could be another reason for faster recovery and more regrowth potential. More reserves and remaining leaf area may also be the reason for more regrowth potential in rocket compared to pak choi. Another important reason for the better performance of lettuce was that temperatures during the growing season were in the range of optimum temperatures (12-21 ºС), except for the regrowth between the second and third harvests in the LS. This relates to higher photosynthetic rates and in turn leads to faster recovery and regrwoth. Lettuce was the most suitable crop in the reaping and regrowth system in this experiment. However, rocket might also be appropriate for this system, particularly if the price is high enough to make it economically viable.

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: The aim of this study was to determine the effect of a grass herbicide, a broadleaf herbicide with some grass control capabilities, method of tillage (tine and no-tillage) at planting of wheat as well as different medic cultivars on the regeneration, dry matter (OM) production and quality of a medic pasture. The trial was conducted at Langgewens experimental farm in the Swartland wheat producing area. Nine medic cultivars of three different species were evaluated after being sprayed with either haloxyfop-R-methyl (HAL) ester or imazamox (IMI) and subjected to either a tine tillage or a no tillage treatment at planting of wheat. Soil samples were taken during January 2000 to determine the size of the medic and weed seedbank as well as the degree of dormancy in the medic seeds, while OM samples were taken throughout the growing season to determine the OM production of the different medic cultivars and weed species. OM samples taken during October 1998 on the same pasture, were used to determine the crude protein (CP) and neutral detergent fibre (NOF) content of the pasture. The samples were subjected to in vitro digestion and the digestibility of pasture CP (OCP), NOF(ONOF) and DM (DOM)were determined. Results showed that seedling establishment differed between cultivars used, herbicide treatments applied as well as the crop stage in the rotation. The cultivars produced more seedlings where IMI was applied compared to HAL as well as where the area consisted of two year pasture compared to one year pasture (1998) and one year wheat (1999). After a year of pasture and a year of wheat, cultivars Sephi and Paraggio produced the most seedlings, while Caliph and Orion produced the least. Caliph however, showed a very high degree of seed dormancy while Orion's low seedling establishment was due to its sensitivity to the IMI herbicide used. Little difference was found between the nine cultivars early in the season (July - August) with regard to cumulative OM production, except for Orion, whose growth was severely damaged by the IMI treatment. At the end of the growing season (October), the cultivar Caliph's cumulative OM production (2010.1 kg/ha) was significantly higher than all the other cultivars, except for Parabinga (1053. 4 kg/ha). Oifferent pasture samples, of which the botanical composition was known, was analysed for CP, NOF, OOM, OCP and ONOF. There was no significant difference in pasture composition during 1998 but variation in the pasture composition did however cause the IMI treatment, compared to the HAL treatment, to have a lower ONOFand OOMcontent. A modelling procedure was used to predict the pasture quality parameters (CP, NOF, OOM,OCP and ONOF) from the pasture composition (medic hay, medic pods, grassy and broadleaf weeds). This prediction of CP, NOF, OOM, ONOF and OCP from the pasture components had a relative low accuracy (49 -74.1 %) and a further refinement of this model for possible use on farms in order to improve grazing management and animal production is advised. In conclusion it could be said that broadleaf weed control caused a definite increase in medic seed and OMproduction, but Orion should not be used with an IMI herbicide. All the cultivars, except for Orion, produced enough seedlings up to the second year to ensure sustainability of the medic pasture. All the cultivars, except for Orion, produced a sufficient amount of OM early in the growing season. Caliph however, produced by far the most OM later in the growing season. A reduction of broadleaf weeds and medic pods will increase the digestibility of NOFand OMand therefore increase the quality of the pasture. Pods however are an important part of summer forage and the aim should therefore rather be to reduce the number of broadleaf weeds in the pasture.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van 'n gras en breëblaar onkruiddoder (wat sekere grasse beheer), metode van bewerking tydens die saai van koring asook nege verskillende medic kultivars op die regenerasie, droë materiaal produksie en kwaliteit van medic weidings te bepaal. Die proef is gedoen op Langgewens proefplaas wat geleë is in die Swartland koring produserende gebied. Nege medic kultivars is geëvalueer nadat die weiding met of haloxyfop-R-metiel ester (HAL) of imazamox (IMI) onkruiddoders gespuit is en onderwerp is aan of 'n vlak tand of geen bewerking tydens die saai van koring. Grondmonsters is geneem in Januarie 2000 om die grootte van die medic en onkruid saadbank asook om die graad van dormansie in die verskillende medic kultivars se sade te bepaal. Droë materiaal monsters is gedurende die 2000 groeiseisoen geneem om die droë materiaal produksie van die verskillende medic kultivars asook onkruid spesies te bepaal. Droë materiaal monsters is gedurende Oktober 1998 geneem en gebruik om die ruproteïn (CP) en neutraaloplosbare vesel (NDF) inhoud van die weiding te bepaal. Die monsters is in vitro verteer en die verteerbaarheid van CP (OCP), NDF (ONOF) en droë materiaal (DOM) is bepaal. Resultate wys dat saailing vestiging verskil tussen die verskillende kultivars wat gebruik is, verskillende onkruiddoder behandelings asook die stadium van die weidings/koring. Die kultivars het meer geproduseer waar die weiding met IMI behandel is in vergelyking met waar HAL toegedien is, asook waar koring nog nie gesaai is nie. Na 'n jaar van weiding en 'n jaar van koring, het die kultivars Sephi en Paraggio die meeste saailinge, en Caliph en Orion die minste saailinge gehad. Caliph het egter 'n hoë graad van dormansie in sy saad getoon, terwyl die swak vestiging van Orion die gevolg is van die kultivar se hoë sensitiwiteit teenoor IMI. Min verskil is gevind tussen die nege kultivars, vroeg in die groei seisoen (Julie - Augustus), wat kumulatiewe droë materiaal produksie betref, behalwe vir Orion wat erg beskadig is deur die IMI behandeling. Aan die einde van die groeiseisoen (Oktober 2000) was die kumulatiewe droë materiaal produksie van die kultivar Caliph (2010.1 kg/ha) betekenisvol hoër as al die ander kultivars behalwe vir Parabinga (1053.4 kg/ha). Weidingsmonsters, waarvan die botaniese samestelling bekend was, is ontleed vir CP, NDF, DDM, DCP en DNDF. Daar is geen betekenisvolle verskille gevind in die botaniese samestelling van die weidingmonsters geneem in 1998 nie,maar die variasie in botaniese samestelling het veroorsaak dat IMI in vergelyking met HAL 'n laer DNDF and DDM inhoud het. 'n Model is opgestel wat die weidingskomponente (medic hooi, medic peule, gras en breëblaar onkruide) gebruik om die kwaliteits parameters (CP, NDF, DDM, DCP en DNDF) van die weiding te skat. Hierdie skatting van CP, NDF, DDM, DCP en DNDF deur van die weidingskomponente gebruik te maak het 'n relatiewe lae akuraatheid gehad (49 -74.1 %) en verdere verfyning van hierdie model vir moontlike gebruik op plase, ten einde weidings bestuur en diere produksie te verbeter, word voorgestel. Die gevolgtrekking kan gemaak word dat breëblaar onkruidbeheer 'n definitiewe verbetering in die medic saailing en droë materiaal produksie van die medies te weeg gebring het, maar die kultivar Orion behoort nie saam met 'n IMI gebruik te word nie. AI die getoetste kultivars, behalwe Orion, het voldoende saad oorlewing vertoon tot en met die tweede jaar van die rotasie om lewensvatbaarheid van die sisteem te verseker en alle kultivars, behalwe Orion, het voldoende droë materiaal produseer vroeg in die groeiseisoen. Caliph het egter laat in die groeiseisoen by verre die meeste droë materiaal geproduseer. 'n Vermindering in die hoeveelheid breëblaar onkruide en peule in die weiding sal tot 'n verhoging in die verteerbaarheid van NDF en DM lei en dus 'n verhoging in die kwaliteit van die weiding tot gevolg hê. Peule is egter 'n belangrike bron van voedsel aan weidende diere gedurende droë somermaande en die verbetering van weidings moet eerder gedoen word deur te poog om breëblaar onkruide te beheer.

Nos sistemas agropecuários (SA) o meio-ambiente, o solo, os animais e as plantas são componentes indissociáveis no processo de produção. Além disso, nesses sistemas o tempo de produção é relativamente longo. Essas características dos SA incrementam o risco e a incerteza associados às alternativas de decisão tomadas no processo de produção. Uma ferramenta que pode ser utilizada para auxiliar esse processo são os modelos matemáticos. Os modelos são uma representação simplificada da realidade e permitem estimar a resposta (e.g., produção) de um sistema face a alterações no processo e/ou descrever e compreender alguns dos processos que ocorrem dentro deste. Este trabalho teve como objetivos (i) testar o modelo Stockpol ® nas condições e sistemas de produção de ruminantes em pastagens brasileiros, (ii) validar um modelo de acúmulo de forragem em função de variáveis climáticas, e (iii) avaliar modelos para estimar consumo de forragem em sistemas de produção de ruminantes em pastagens. Para esse propósito foram identificadas publicações com informações suficientes que pudessem ser utilizadas nos exercícios de validação e avaliação modelos testados. As informações selecionadas sobre os sistemas de produção utilizados no Brasil foram catalogadas em três bancos de dados: pastagens, bovinos e indicadores de preços e insumos. Esse trabalho de organização dos bancos de dados permitiu identificar áreas carentes de pesquisa (como, por exemplo, a estacionalidade de produção forrageira e consumo de forragem por animais em pastejo) além da necessidade de se padronizar os procedimentos metodológicos, para que se possa comparar e integrar os resultados obtidos diversas regiões do Brasil. Apesar das limitações encontradas, se forem realizados ajustes nos parâmetros e/ou a inclusão de novas variáveis no modelo Stockpol ® , esse poderá vir a ser uma ferramenta de auxílio à pesquisa e ao processo de tomada de decisão nos sistemas de produção de ruminantes em pastagens do Brasil. O Modelo de Unidades Fototérmicas (UF) proposto é adequado para estimar a produção de Cynodon spp. desde que os fatores de variação sejam unicamente fotoperíodo e temperatura. Nesse modelo as simulações deverão ser realizadas para períodos entre 28 e 42 dias, e a temperatura base utilizada entre 13 e 15 ºC. No futuro, mais variáveis (e. g. balanço hídrico) poderão ser incorporadas ao modelo a fim de melhorar a exatidão das suas estimativas. O modelo avaliado para estimar consumo de forragem por ruminantes em pastejo deverá ser reparametrizado e/ou utilizar a oferta de folhas (massa de folhas verdes dividida pelo peso vivo animal, ambos numa mesma área de pastagem), quando aplicado a sistemas que utilizem pastagens de clima tropical. O modelo para estimar desempenho não estimou corretamente o ganho de peso dos animais, provavelmente devido à superestimativa do custo energético do pastejo e/ou da subestimativa do valor nutritivo da dieta selecionada pelos animais. Espera-se que solucionado essa questão, o modelo de desempenho animal possa trabalhar em conjunto com os modelos de UF e de consumo de forragem para que assim seja possível realizar simulações de um sistema de produção de ruminantes nas condições climáticas brasileiras e com pastagens de clima tropical.
In agricultural systems, environment, soil, animals and plants are indissociable components of the production process. Furthermore, the production time-frame is relatively long. These characteristics enhance risk and uncertainty associated with decision alternatives made during the process. One tool which can aid in decision-making in these processes is the use of mathematical modeling. Models are simplified representations of reality and allow for the estimation of responses of the system (e.g., production) as the process is altered or for the description and understanding of processes within the system. The objectives of the present study were to (i) test the Stockpol ® model under the conditions and as a predicting tool for ruminant production systems in Brazil, (ii) validate a herbage accumulation model based on climatic variables, and (iii) evaluate models that estimate forage intake on pasture-based animal production systems. For these purposes, the available literature was surveyed in order to identify the datasets that would fulfill the necessary requirements in terms of amount of information needed for the validation and evaluation exercises. The information were then catalogued in three separate datasets: pasture, animal, and economic indicators. This work allowed for the identification of research areas where information is short (such as the seasonal distribution of annual forage production as well as forage intake by grazing animals), besides the need for standardization of research methods and procedures so that research data generated in different environments and by different research groups in Brazil can be compared on the same basis. Despite the many limitations, if the existing parameters are reviewed or adjusted and/or new input variables are incorporated, the Stockpol ® model may become both a research and a decision-making tool for pasture-based animal production systems in Brazil. The Photothermal Units (PU) model proved suitable as it gave adequate predictions of forage yield of Cynodon spp. grasses considering only daylength and temperature as input variables. In this model, predictions seem to be most accurate when the base-temperature is between 13 and 15 ºC. In the future, more input variables, such as the hidric balance (to fine-tune the water budget) may be incorporated into the model to enhance its prediction ability. The model evaluated to predict forage intake by grazing ruminants will likely need reparametrization and/or use green leaf allowance (green leaf dry mass divided by total liveweight at any one point in time) to be useful in predicting intake on tropical pastures. The model used to predict performance gave poor estimates of weight gain, probably due to the overestimation of the energy cost of grazing and/or the underestimation of the nutritive value of the diet selected. It is expected that, once these issues have been resolved, the performance model can operate in conjunction with both the PU and the intake models so that the major components of the system can be simulated under Brazilian conditions

Kiwifruit are of huge economic importance for New Zealand representing 29 percent of total horticultural exports. Fruit size is the biggest determinant of what consumers are willing to pay, and there is also a positive relationship between consumer preference for flavour and percentage dry matter. The two main cultivars exported from New Zealand are Actinidia chinensis ‘Hort 16A’ (gold kiwifruit) and A. deliciosa ‘Hayward’ (green kiwifruit). Under current commercial practice the only product allowed for use on kiwifruit to increase fruit size in New Zealand is Benefit®. Benefit® has been shown to induce different results when applied to A. chinensis and A. deliciosa, whereas synthetic plant growth regulators such as the cytokinin-like substance N-(2- chloro-4-pyridyl)-N’-phenylurea (CPPU) have been found to promote similar increases in fresh weight of fruit in both cultivars. Final fruit size is determined by both cell division and cell enlargement. It was been shown that fresh weight can be increased in both of the major Actinidia cultivars even though their physiology differs. Hormonal control of fruit size in relation to cell division and cell enlargement phases of fruit growth was studied in both A. chinensis and A. deliciosa. CPPU was applied to both cultivars in a growth response experiment where fruit were collected throughout the growing season. The objective of this experiment was to create growth curves, to compare and contrast the effect on A. chinensis and A. deliciosa, and to provide material for hormone analysis. Application of CPPU was found to significantly increase the fresh weight of both A. chinensis and A. deliciosa fruit (46.98 and 31.34 g increases respectively), and alter the ratio of inner and outer pericarps of A. chinensis fruit. CPPU and Benefit® were applied individually and together to both cultivars. It was found that only A. chinesis fruit were affected by the application of Benefit®; fresh weight was increased by 26.38 g, and percentage dry matter was significantly reduced. There was a statistically significant (p < 0.05) interaction between CPPU and Benefit® when applied to A. chinensis. 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) was applied to A. deliciosa on two application dates at three concentrations and was found to decrease fresh weight of fruit, but significantly increase percentage dry matter regardless of application date or concentration. Lastly CPPU and 1-naphthalene acetic acid (NAA) were applied to A. deliciosa at two application dates and in all combinations. Application date affected the response to both a low concentration of CPPU and NAA. A synergistic interaction was observed when CPPU was applied early plus NAA late (CPPU early (4.53 g increase) plus NAA late (13.29 g) < CPPU early plus NAA late (33.85 g). Finally endogenous hormone content was studied. Methods were developed and tested for the simultaneous analysis of both indole-3-acetic acid (IAA) and cytokinins. Freeze dried fruit were purified using Waters Sep-pak® cartridges and Oasis® columns then IAA was quantified by high pressure liquid chromatography. Preliminary results indicate a correlation between application of CPPU and endogenous IAA, high concentrations of IAA correlated well with periods of rapid fruit growth particularly for CPPU treated fruit.

There is an extensive debate on the potential environmental impact of dairy farms and in particular the effect of dairy farms on the nitrogen cycle and the effect that this has on ecosystems. Within New Zealand and in particular in the South Island, the expansion of dairying and the adoption of new dairy systems has led to this becoming an increasingly important issue, locally through its effect on water quality and the environment and nationally and internationally through the production of green house gases. Increases in nitrogen usage at the expense of clover nitrogen fixation, irrigation, stocking rate and the introduction of dairy cows onto light free draining soils previously the preserve of arable or sheep farming has led to concern as to the effect intensive pastoral dairying may have on the nitrogen dynamics of the farm and the environment. This study is designed to assess how changes in grazing management in particular changes in pre-grazing and post-grazing residuals alter the clover/ryegrass balance on the farm and the effect that this has on the farm’s nitrogen dynamics. The effects of qualitative changes in grazing management on pasture composition are well established but little is known of the effect of quantitative changes in pasture management on composition, in particular the effect of grazing residuals. There are a number of detailed models of the physiological processes in the energy and nutrient cycling in plants, animals and the soil. There are a smaller number of whole farm models that through integration and simplification of component models attempt to represent the flux of nutrients though a dairy farm. None of these whole farm models is currently able to model the nitrogen flux through a dairy farm at a sufficient level of resolution to capture differences in pasture composition as these occur spatially, temporally and in response to grazing management. This project sought to better understand the nitrogen dynamics on a dairy farm by constructing and then linking component models – a pasture composition and growth model, a cow model, an excretal return model, a soil model and a water balance model – within a whole farm management schedule. The formal null hypothesis is that the mechanistic, mathematical model constructed for this PhD cannot capture and explain the full range of the changes in soil water content, soil nitrogen status, pasture production and composition and animal production, following the alteration in management of the dairy farm between 2002 and 2004. Individual component models were constructed by the author using the computer software package (Matlab) and validated against data extracted from the literature. The models were then converted into one simulation package using C-sharp as the source code language by Elizabeth Post, Senior Computer Scientist at Lincoln Ventures Ltd, Lincoln, New Zealand and the author. This model was then used to investigate the nitrogen dynamics of a dairy farm: the relationship with pasture composition and whether small changes in pasture residuals make a difference to pasture composition and nitrogen dynamics. Two different simulations were run based on the management practice of Lincoln University Dairy farm (LUDF) over two dairy seasons (2002-03 and 2003-04) and validated against the data recorded on this farm. In 2002-03, 50 cows were over wintered and 580 cows were subsequently milked on 200ha. Post grazing residuals where maintained at 1600-1750KgDM/ha. In 2003-04, 125 cows were overwintered and 635 cows were milked on 200ha with post grazing residuals maintained at 1400KgDm/ha. All models operate on a daily time step. Within the pasture model composition is described by 9 state variables describing different components of the pasture and pasture growth is modelled mechanistically from a calculation of component photosynthesis. A further 9 state variables describe the nitrogen composition of the pasture components. The soil model is a variable two layer, mechanistic representation, parametised for the shallow, stony soils of LUDF. Soil water status is an input for the pasture model while water uptake by the growing plants affects the soil water balance within the soil model. Animal intake and production are modelled mechanistically with model cows described in terms of their age, genetic merit, body weight, breed, pregnancy status, conception date and body condition score. Each cow type produces a different quantity of urinary and faecal excretion which varies with dry matter intake, milk yield and the sodium and potassium status of the pasture. Excretal nitrogen composition is predicted within a separate model which calculates daily nitrogen excretion in faeces, urine and milk. Excretions are deposited randomly over the grazed area and account is taken of overlapping excretions that are created on the same day and overlaps that occur with older excretal patches deposited in previous grazing rounds. Each excretal patch has its own associated pasture, water and soil model reflecting the differences in nitrogen status between patches. Grazing preference is expressed within the model between different classes of excretal patch and between excretal patches and the base pasture and between clover and grass. Supplementary silage is conserved and fed according to the management schedule of LUDF. Cows calve, become pregnant and are dried off within the model according to the relevant records from LUDF. Cows are deemed to arrive on the farm on the day of calving and to leave on the day that drying off is finished (a 5 day procedure within the model), except for those cows that are overwintering which remain on the farm. The soil model has multiple nitrogen/carbon pools and is dynamically linked to all the other models. External nitrogen losses from the system are modelled as volatilisation, leaching and denitrification, with pasture nitrogen uptake from the soil model and fixation by clover from the atmosphere. Both the individual component models and the final assembled composite model were successful in matching the available data in terms of pasture and animal production, pasture composition, soil water balance and nitrogen status and external losses. The model indicates that the low residual, high stocking rate farm returns more excreta to the soil. However, this is countered by a reduction in the amount of dead material returned to the paddock and this reduces the relative size of the pool of nitrogen in the dead organic matter. This produces a relative lack of substrate for the soil microbes which are thus unable to exploit all of the nitrogen in the available pool. Soil ammonium and nitrate pools are also increased from the increase in faecal and urinary return so precipitating an immobilising flux from these larger pools to the smaller pool of nitrogen available to the soil microbes. However, the relative inability of the soil bacteria to fully exploit this means that the production of soil organic live matter and the resulting mineralising flux from the dead organic matter pool through the available pool to the ammonium and nitrate pools is reduced. The larger ammonium and nitrate pools will also be associated with increased external losses from the system as denitrification, leaching and volatilisation are increased. The increase in the clover percentage within the sward in 2003-04 led to greater nitrogen fixation and the model suggests that some of the extra nitrogen is effectively captured by the animals in increased production. However, the reduction in the return of dead matter coupled with an increase in excretal return and the consequent increase in the mineral nitrogen pools within the soil lead to greater losses of nitrogen from the soil.

A series of experiments was carried out on cultivated oat (Avena sativa L. cv Amuri) to examine the efficacies of fluazifop-butyl and glyphosate against water stressed plants, plants grown in low and high nitrogen and plants treated with gibberellic acid (GA₃). Avena sativa L. was used as a test plant and on completion of the experiments, further studies were carried out on the weed species wild oat (Avena fatua L.). In the laboratory, plants maintained at wilting point for five days before and nine days after spraying and treated with fluazifop-butyl (0.5 kg a.i./ha) appeared healthy 32 days after herbicide application, while plants supplied with water throughout the experiment were completely chlorotic/necrotic and had main stem detachment from within the leaf sheaths. In the field, plants maintained unirrigated until 14 days after spraying with fluazifop-butyl (0.25 kg a.i./ha) or glyphosate (0.18 kg a.i./ha) showed greater tolerance to the herbicides than plants irrigated regularly. Values for seed head yield for water stressed and irrigated plants, 45 days after applying fluazifop-butyl, were 66 g and zero g dryweight/m² respectively. Comparable values for glyphosate treated plants were 65 g and 25 g dryweight/m². Radiolabel studies indicated that in comparision with well watered plants, water stressed plants absorbed 20% less applied ¹⁴C-glyphosate. In addition, the proportion of absorbed ¹⁴C-glyphosate translocated from the treated leaf was 15% less under water stress conditions. Uptake of ¹⁴C-fluazifop-butyl was similar under well watered and water stress conditions and was 30-40% of that applied. The proportion of absorbed ¹⁴C-activity which was transported was very low, but was greater under well watered conditions (7.6%) than under water stress conditions (4.4%). Under well watered conditions in the laboratory and field, fluazifop-butyl (0.25 kg a.i./ha) and glyphosate (0.18 kg a.i./ha) were less toxic at low nitrogen than high nitrogen. For example, 34 days after spraying with fluazifop-butyl under laboratory conditions total plant dry weight was 1.51 g and 0.56 g at 1.0 mol/m³ and 10 mol/m³ applied nitrate respectively. As with soil water content, soil nitrogen content had no effect on uptake of fluazifop-butyl. However, the proportion of absorbed fluazifop-butyl which was translocated out of the treated lamina was greater under high nitrogen conditions (26.1 %) than under low nitrogen conditions (9.3%). Under laboratory conditions, addition of 200 µg GA₃to the leaf sheaths two days prior to spraying with fluazifop-butyl or glyphosate increased the efficacy of both herbicides at low nitrogen. Similarly, under field conditions application of GA₃ (0.21 kg/ha) two days prior to spraying with glyphosate increased the performance of the herbicide against Avena sativa L. growing in a nitrogen depleted soil. At harvest, seed head yield for GA₃ treated and non-treated plants was zero and 7.4 g dry weight/m² respectively. Experiments with Avena latua L. showed that this species was tolerant of fluazifop-butyl and glyphosate when grown in low water or low nitrogen conditions. Under water stress conditions, pre-treatment with GA₃ increased the phytotoxicity of fluazifop-butyl to Avena latua L. Similarily, GA₃ enhanced the phytotoxicity of glyphosate to Avena latua L. grown under low nitrogen conditions. Reduced performance of fluazifop-butyl under stress conditions involves a reduction in translocation of herbicide to meristems, but other factors are likely to be involved. It was concluded that for glyphosate, reductions in uptake and translocation of the herbicide are important factors causing reduced performance of this herbicide under stress conditions. Possible reasons for GA₃ enhancement of fluazifop-butyl and glyphosate activity under stress conditions are discussed and the potential of growth regulators as adjuvants is considered.

Despite the importance of a high white clover (Trifolium repens) content in temperate pastoral systems in terms of livestock performance and nitrogen fixation, the proportion of white clover in grass-clover pastures is often low (<20%). This thesis examined in two experiments whether the white clover content of pastures could be improved by sowing white clover with alternative grass species to diploid perennial ryegrass (Lolium perenne L.). In a pasture experiment, DM production, pasture composition and morphology of grass-clover mixtures was measured over the establishment year (January 2007 to January 2008) where white clover was sown in fine mixtures with diploid perennial ryegrass, tetraploid perennial ryegrass, timothy (Phleum pratense L.) and cocksfoot (Dactylis glomerata L.). Pastures were irrigated and rotationally grazed with on-off grazing with Coopworth ewe hoggets. Total annual DM production of pasture was more than 20% higher in tetraploid (12521 kg DM ha⁻¹) and diploid (11733 kg DM ha⁻¹) perennial ryegrass than timothy (9751 kg DM ha⁻¹) and cocksfoot (9654 kg DM ha⁻¹). However, timothy (5936 kg DM ha⁻¹) and cocksfoot (5311 kg DM ha⁻¹) had more than four times higher white clover annual DM production than tetraploid (1310 kg DM ha⁻¹) and diploid (818 kg DM ha⁻¹) ryegrass. Pasture growth rate at the first three harvests in autumn was significantly greater in tetraploid and diploid ryegrass than timothy and cocksfoot. Timothy and cocksfoot had a higher proportion of white clover than tetraploid and diploid perennial ryegrass throughout the entire year. This was due to more and larger white clover plants in timothy and cocksfoot plots. In a grazing preference experiment, the partial preference of sheep for white clover offered in combination with the same grass species as in the pasture experiment was measured in five grazing tests in May, September, October, November and December 2007. Pastures were sown in January 2007. Paired plots (grass and clover both 4.2 m x 10 m) were grazed by three Coopworth ewe hoggets between 9am and 5pm, and preference was recorded by decline in pasture mass and visual scan sampling for grazing time. Grazing preference for clover was generally low throughout these tests (e.g. average apparent DM intake from clover = 47%; average grazing time from clover = 44%). Several explanations are proposed for this low preference including a high N content and intake rate of the grass relative to the clover. No significant differences were found among the grass treatments in total grass grazing time, total clover grazing time, ruminating time, the proportion of grazing time on clover, selective coefficient for clover and DM intake percentage from clover at any date. There was no significant change in overall sward surface height (SSH) decline among grass treatments throughout all the tests except December 2007 when the overall SSH decline for cocksfoot was significantly lower than the other species. The study indicated that the rapid growth rate of perennial ryegrass in the early phase of pasture establishment, rather than differences in partial preference, was the key factor limiting white clover content in the mixed swards relative to cocksfoot and timothy pastures. It is concluded that high clover-containing pastures capable of delivering high per head performance can be established through the use of slow establishing pasture species such as timothy and cocksfoot.

Genotypic differences in growth and yield of two common bean (Phaseolus vulgaris L) cultivars to Rhizobium inoculation and management were investigated. In 2003-04, the two bean cultivars (Scylla and T-49) were combined with three inoculant treatments (strains CC 511 and RCR 3644, and a control of no inoculation), two fertiliser levels (0 and 150 kg N ha⁻¹) and two irrigation treatments (irrigated and rainfed). There was no nodulation on either cultivar. To further investigate the symbiotic relationship, 16 rhizobial isolates, including the two used in the first field experiment, were combined with the cultivar Scylla and evaluated in a greenhouse. Subsequently, five Rhizobium isolates were chosen for further field evaluation, based on signs of early nodulation in the greenhouse trial. The second field experiment in 2004-05 combined the five inoculant strains (RCR 3644, UK 2, H 20, PRF 81, PhP 17 and a control) with two bean cultivars (Scylla and T-49). In the greenhouse, nodule number varied from 7 (UK 2) to 347 (H 441) nodules plant⁻¹ at 51 DAS and from 13 (UK 1) to 335 (CIAT 899) nodules plant⁻¹ at 85 DAS. In 2004-05, in the field, nodulation was also variable, ranging between 1 and approximately 70 nodules plant⁻¹, with higher nodules numbers plant⁻¹ being found on cultivar T-49. Of the isolates used in the field, strains H 20, PRF 81 and PhP 17 produced 70, 25 and 12 nodules plant⁻¹ at 70, 40 and 54 DAS respectively. Nodules formed were of various sizes and more than 80 % were pink to dark red in colour denoting the presence of leghaemoglobin and active N fixation. The remaining nodules were either green or white. The importance of selecting an appropriate cultivar for the growing conditions was highlighted in these experiments. Leaf area index, leaf area duration intercepted radiation and final utilisation efficiency were significantly affected by cultivar. In both seasons cv. T-49 reached maturity (dry seed) before Scylla, while unirrigated plants reached green pod maturity seven days before irrigated plants. Plants of cv. Scylla gave a final TDM of 730 g m⁻²; compared to the 530 g m⁻² produced by T-49. The average growth rate was 7.0 and 5.2 g m⁻² day⁻¹ for Scylla and T-49 respectively (2003-04). Plants receiving 150 kg N ha⁻¹ produced 665 g m⁻² TDM which was 12 % more than was produced by unfertilised plants. The application of 150 kg N ha⁻¹ gave an average growth rate of 6.4 g m⁻² day⁻¹ compared to 5.7 g m⁻² day⁻¹ from plants with no N. Inoculation in the field had no significant effect on TDM in both seasons. Temperature affected growth and DM accumulation. Accumulated DM was highly dependent on cumulative intercepted PAR. Air temperatures below the base temperature (10 °C) affected growth in 2004-05, resulting in plants accumulating just 0.24 g DM MJ⁻¹ PAR during early growth. This increased to 2.26 g DM MJ⁻¹ PAR when the temperature was increased above the base temperature. There was a strong relationship between LAI and intercepted PAR. A LAI of 4.0-4.5 was required to intercept 90-95 % of incident solar radiation. Cultivar significantly (p < 0.001) affected radiation use efficiency (RUE). Scylla had a RUE of 1.02 g DM MJ⁻¹ PAR compared to T-49 at 1.18 g DM MJ⁻¹ PAR. Seed yield was significantly (p < 0.001) affected by cultivar and fertiliser application. Cultivar Scylla produced 467 g m⁻² which was 76 % more than T-49, while a 12 % increase in seed yield was observed in N fertilised plants over unfertilised plants. Only cultivar significantly affected HI, while the yield components that had the greatest effect on seed yield were hundred seed weight and pods plant⁻¹. Inoculation significantly (p< 0.05) affected 100 seed weight (2004-05). Plants inoculated with strain H 20 had the highest 100 seed weight at 25.2 g with cv. Scylla producing larger seeds than T-49. The belief that local environmental conditions play a major role on field survival of bacteria, led to the use of PCR methods to identify field nodulating organisms. Amplification of genomic DNA from parent isolates using primers fC and rD generated a single band for each isolate. Isolates were identified to the species level as either Rhizobium or Agrobacterium, using the highly conserved internally transcribed spacer (ITS) region and are known to nodulate common bean. The DNA extracted from the isolates recovered from nodules of field grown beans gave multiple bands with primers fC and rD. Five distinct banding patterns were observed. All of these were different from those of parent isolates. Sequencing of the 16S rRNA demonstrated that nodules of field grown beans in Canterbury were inhabited by Pseudomonads either alone or in association with other root nodulating organisms. The inability to identify the inoculant strains in nodules of field grown beans does not rule out their infection and nodulating function in the cultivars used. The results suggest the possibility of both Rhizobium and Pseudomonads cohabiting in the nodules of field grown beans. The aggressive nature of Pseudomonads on artificial media, possibly out competing the inoculant rhizobia is proposed, leading to the inability to identify the inoculant strain from the nodules of the field grown beans by PCR methods. The need to identify the nodule forming or nodule inhabiting bacteria in the nodules is necessary to classify the importance of these organisms and their economic benefit to agricultural production. This study also underlines the importance of using PCR methods to gain valuable insights into the ecological behaviour of Rhizobium inoculants and nodule inhabiting organisms.

This study was undertaken to research the principles and practices behind increased pasture productivity on Longslip Station, Omarama. A range of landscape - soil - climate - plant systems were identified, then analysed and the legume responses measured. By isolating cause and effect and appreciating the driving variables of each system, lessons learnt could be reliably and objectively transferred to the rest of the farm. Extrapolation to the balance of the property (15,150 ha) permitted immediate large-scale development and engendered confidence to lending institutions, Lands Department, catchment authorities and ourselves. Soil (land) cannot be well managed and conserved unless it is mapped reliably and its characteristics measured and interpreted by skilled observers (Cutler, 1977). Soil resource surveys, and their interpretation, are an essential ingredient of rational resource evaluation and planning. This thesis is a figurative and comparative survey and study of the soil catenary bodies, resident vegetation, legume establishment and pasture production characteristics of a 400 hectare catchment, in relation to, and as influenced by soil landscape unit, slope component, altitude, aspect and time. The inherent diversity in landform, soil properties and vegetation communities in a single catchment in the high country has not previously been fully studied or appreciated. This has lead to blanket recommendations for fertilizer, seed and management regimes both within and between properties and even regions. This study reports on the diversity of, yet predictable change in soil properties with slope position (upper, middle and lower) aspect and altitude in terms of both soil physical properties e.g. soil depth and water holding capacity and soil chemical properties such as pH, BS%, %P, %S, %N and %C. The composition of the resident vegetation and its differential response to oversowing and topdressing and subsequent change through time is reported and discussed. Finally an epilogue gives an insight into the problems and frustrations of farming practices in the high country from a motivation and personal perspective and political point of view that it is essential to come to terms with.

Manure production and nutrient management in pasture-based dairy production systems by Walter Svinurai The effect of dietary treatments on nutrient excretion was determined and an attempt to improving the retention of excreted nitrogen in stored manure using Aloe ferox leaf gel (AFLG) and pine bark was conducted at a pasture-based dairy farm. The animal mass-balance method was used to determine nutrient excretion by cows fed on three dietary treatments, Lolium perrene-based treatment (LP), Lolium multiforium-based treatment (LM) and Lolium perenne- Trifolium repens -based treatment (LTF). In separate experiments, slurry from dairy cows fed LM was amended with AFLG and pine bark at concentrations of 25, 50, 75 and 100 g/l and stored under anaerobic conditions for 16 days. The highest and lowest excretions of N, P and K were observed in LM and LP treatments, respectively. Increasing dietary N improved K and N retention in milk and, consequently increased milk urea nitrogen (MUN) and N excretion (P < 0.05). The concentrations of AFLG affected N and P retention in manure (P < 0.05). The highest retention in total Kjeldahl nitrogen (TKN) of the initial was 42% AFLG at 25g/l inclusion rate. Ammonium nitrogen (AMN) concentration increased significantly due to the interactive effect of AFLG inclusion rate and time. Pine bark powder significantly improved N and P retention in manure at all concentrations. The retention in TKN was higher (P < 0.05) at 25g/l pine bark powder than other concentrations. The interaction effect of inclusion rate and time increased iii AMN (P < 0.05). Dietary treatments significantly affected nutrient excretion, and AFLG and pine bark considerably improved N retention in stored slurry. Findings from the filed trial suggest the need for more attention on managing dietary nutrients in the post-rainy and cool-dry season when growth of pasture influenced choice of dietary treatments that led to high nutrient excretion. Field simulation of the additives to determine their efficacy and environmental hazards was recommended.

Herbicide sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate glass-legume ratios. A study was conducted to investigate the viability of sod suppression by sheep grazing or mowing, as alternatives to herbicide, during pasture renovation with no-till seeding of red clover (Trifolium pratense L.) or white clover (Trifolium pratense L.). Sod suppression methods evaluated were: strategically timed mowing or sheep grazing to 5 or 10 cm at seeding and during legume establishment, or similarly managed mowing or sheep grazing with an additional defoliation to 5 cm the previous fall. Additional treatments included suppression by herbicide and, unsuppressed and unseeded controls. Treatments were evaluated by determining clover plant population, botanical composition, forage yield and quality. Physical (mowing or grazing) and herbicide sod suppression resulted in similar clover plant populations; clover yields tended to be higher with herbicide suppression. However, increasing the intensity of physical suppression increased clover yields. Forage quality was increased only with sod suppression by grazing or herbicide when compared with the unimproved control. Although, for grazing this was attributed to a more frequent defoliation regime and not to the renovation itself. Unlike suppression with herbicide, physical suppression did not decrease total seasonal forage yields in the renovation year when compared with controls.

Thesis (MScAgric)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Poor water management and poor water use efficiency (WUE) have been identified as one of the major problems experienced by vegetable growers in most of the developing countries, including South Africa. This poor management and poor utilization of water have led to a drastic decline in the quality and quantity of available water. In South Africa agriculture uses about 50% of available water. Increasing water demand for domestic, industrial and mining uses, may decrease agriculture's share to less than the current 50%, henceforth, better utilization of this resource is imperative. Selection of a good irrigation system can limit water loss considerably. Some irrigation systems have a potential to save more water than others do. Since irrigation systems affect the WUE of crops, care should be taken when selecting an irrigation system under conditions of limited water quantity. Ebb-and- Flood watering systems have been introduced for effective sub-irrigation and nutrient delivery within closed systems. Such a system was adapted in South Africa, to develop a vegetable production unit for use by families in rural communities, while saving substantial amounts of water. A need to further improve the WUE of this system was subsequently identified. Two studies were conducted at the experimental farm of the University of Stellenbosch (Department of Agronomy). The first trial was conducted under controlled conditions in a glasshouse, and the second under open field conditions. In the first trial, Beta vulgaris (Swiss chard) and Amaranthus spp. ('Imbuya') were grown in two root media; gravel and pumice. In addition, an 'Ebb-and-Flood' and a 'Constant level' system were used with nutrient solutions at two electrical (EC) conductivity levels 1.80 and 3.60 mS cm-I. The results of this (2x2x2x2) factorial experiment indicated that a combination of the 'Ebb-and-Flood' system with gravel as a root medium produced the best results at a low EC, when 'imbuya' was used. A high total WUE was found with 'imbuya', (7.35 g L-I) at EC 1.80 mS cmicompared to a relatively low WUE of 5. 90 g L-I when the 3.60 mS cm-I nutrient solution was used. In the second trial, 'Imbuya's' foliage dry mass, leaf area and WUE was evaluated under field conditions at the Stellenbosch University experimental farm, during the summer of2002. The experimental farm (33°55'S, 18°52'E) is situated in the cooler coastal wine grape-producing region of South Africa with a relatively high annual winter rainfall. This trial was conducted on an alluvial soil, with clay content of 25% and a pH of 5.9 (KC!). A closed 'Ebb-and-Flood' system was compared with two open field irrigation systems ('Drip' and 'Flood') using nutrient solutions at two electrical conductivity levels (1.80 and 3.60 mS cm-i) in all three cases. Foliage dry mass, leaf area as well as WUE was best with 'Drip' irrigation, when a nutrient solution with an electrical conductivity of 3.60 mS cm-i was used. In spite of the fact that additional ground water was available for the soil grown 'Drip' and 'Flood' treatments, the 'Ebb-and-Flood' system outperformed the 'Flood' treatment, especially when the nutrient solution with an EC of 3.6 mS cm-i was used. Insufficient root aeration in the flooded soil could have been a contributing factor. The fact that the 'Ebb-and-Flood' and 'Drip' systems gave the best results when the high EC solution was used to fertigate the plants, may indicate that the plants could have hardened due to the mild EC stress, better preparing them to adapt to the extreme heat that was experienced in the field.
AFRIKAANSE OPSOMMING: Swak: bestuur van water en 'n swak: water-gebruik-doeltreffendheid (WOD) is as een van die belangrikste probleme geïdentifiseer wat deur groente produsente in die meeste ontwikkelende lande, insluitend Suid-Afrika, ervaar word. Hierdie swak bestuur en benutting van water het daartoe bygedra dat 'n drastiese afname in die kwaliteit asook in die kwantiteit van beskikbare water ervaar word. In Suid-Afrika gebruik die landbou-sektor ongeveer 50% van die beskikbare water. Toenemende water behoeftes vir huisgebruik, industrieë en die mynbou mag hierdie 50% aandeel van die landbou sektor laat krimp. Beter benutting van hierdie skaars hulpbron is dus noodsaaklik. Die keuse van goeie besproeiingsisteme mag waterverliese merkbaar beperk aangesien sekere sisteme se water-besparingspotensiaal beter as ander is. Aangesien besproeiingstelsels die WOD van gewasse beïnvloed, is spesiale sorg nodig waar 'n besproeiingstelsel onder hierdie toestande van beperkte waterbronne gekies moet word. 'Ebb-en-Vloed' sisteme kan aangewend word om water en voedingselemente van onder in 'n wortelmedium te laat opstoot en in 'n geslote sisteem te laat terugdreineer. So 'n sisteem is in Suid-Afrika ontwikkel waarmee groente vir families in landelike gebiede geproduseer kan word terwyl water bespaar word. 'n Behoefte om die WOD van hierdie produksiesisteem verder te verbeter is egter geïdentifiseer. Twee ondersoeke is by die Universiteit van Stellenbosch se proefplaas (Departement Agronomie) gedoen. Die eerste proef is onder beheerde omgewingstoestande in 'n glashuis uitgevoer en die tweede onder veld toestande. In die eerste proef is Beta vulgaris (Snybeet) en Amaranthus spp. ('Imbuya') in twee tipes wortelmedia; gruis en puimsteen verbou. 'n 'Ebb-en-Vloed' asoook 'n 'Konstante vlak' besproeiingsisteem is gebruik terwyl voedingsoplossings ook by twee peile van elektriese geleiding (EC) teen 1.80 en 3.60 mS cm-I toegedien is. Die resultate van hierdie (2x2x2x2) fakroriaal eksperiment het aangetoon dat 'n kombinasie van die 'Ebb-en-Vloed' sisteem met gruis as 'n wortelmedium die beste resultate teen 'n lae EC lewer waar 'imbuya' gebruik is. Die WOD met 'imbuya' was hoog (7.35 g L-1) by 'n EC van 1.80 mS cm-I, vergeleke met 'n relatief lae WOD van 5. 90 g L-1 waar die 3.60 mS cm-I voedingsoplossing gebruik is. In die tweede proef is 'Imbuya' se droë blaarmassa, blaar oppervlakte en WOD onder veldtoestande op die Universiteit van Stellenbsoch se proefplaas in die somer van 2002 ge-evalueer. Die proefplaas (33°55'S, 18°52'E) is in die koeler kusstreke van die wyndruif produksiegebied in die winterreëngebied van Suid-Afrika geleë. Hierdie proef is op alluviale grond met 25% klei en 'n pH van 5.9 (KCi) uitgevoer. 'n Geslote 'Ebb-en-Vloed' sisteem is met twee veld-besproeiingsisteme vergelyk ('Drup' en 'Vloed') terwyl voedingsoplossings teen twee peile van elektriese geleiding (1.80 en 3.60 mS cm-I) in al drie gevalle gebruik is. Blaar droëmassa, blaaroppervlakte asook die WGD was die beste met 'Drup' besproeiing waar die EC van die voedingsoplossing 3.60 mS cm-I was. Ten spyte van die feit dat ekstra grondwater vir die 'Drup' and 'Vloed' behandelings beskikbaar was, het die 'Ebben- Vloed' stelsel beter as die 'Vloed' behandeling gedoen veral waar die voedingsoplossing se EC 3.6 mS cm-I was. Swak wortelbelugting was waarskynlik die rede waarom vloedbesproeiing swak produksie gelewer het. Die feit dat die 'Drup' en die 'Ebb-en-Vloed' behandelings in die veldproef die beste gedoen het waar die EC hoog was, mag moontlik met die gehardheid van die plante verband hou wat aan ekstreem warm en dor toestande blootgestel was.

Food security for a growing population presents a significant challenge for crop production, with increasing pressures upon agriculutral productivity. There is a vast need to improve crop yield and quality using an efficient approach that does not present negative environmental impacts. A novel interrogation technique that is able to provide information of the overall health of a plant, would be extremely beneficial in an agriculutral, as well as research, setting. This information could be utilised to better understand the mechanisms of plant functions, including stress responses. Vibrational spectroscopy encompasses a range of techniques that are able to derive chemically specific information from a biological sample in a rapid, nondestructive and cost-effective manner. Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy are two such approaches and have been readily implemented across biological samples. However, their applications in the field of plant science have been relatively underexploited. This is largely associated with the presence of water and fluorescent metabolites found in plant tissues. The application of attenuated total reflectance (ATR)-FTIR and spontaneous Raman spectroscopy for in vivo plant monitoring to elucidate spectral alterations indicative of healthy plant growth in a non-destructive manner. These approaches are able to characterise the biochemical signature of leaves at distinct developmental stages, and correspond to known biological processes within the leaf such as cell wall expansion. This information is useful prior to monitoring studies as normal leaf growth could be considered background variance. No significant local or systemic effects manifest as a consequence of interrogation with these techniques, establishing this as a non-destructive approach for plant system investigations. Raman microspectroscopy as a tool for monitoring nutrient uptake at the leaf surface is also considered, alongside complementary ion probe and elemental analysis. Such a technique is useful in the agrochemical production of foliar fertilisers, where the efficiency of specific formulae can be rapidly compared. This can also further the current understanding of nutrient transport into plant tissues, as well as translocation. Agriculturally relevant levels of calcium were applied to the leaf surface and uptake was successfully illustrated at concentrations as low as 15 mM using Raman microspectroscopy. Ion probe analysis also complemented these findings, with elemental analysis unable to detect this subtle uptake of nutrients. This assay is now being implemented in agrochemical practise as a fertiliser screening method. Deficiencies in essential nutrients such as calcium are detrimental to crop yield and thus are a potential target for improving crop production. A range of spectroscopic methods, including the use of synchrotron radiation, were utilised to presymptomatically detect these deficiencies prior to their onset in live samples. Coupled with multivariate analysis, these techniques discriminate between deficient and control samples with high sensitivity and specificity, without extensive sample preparation that traditional analytical techniques require. These results suggest that Raman and ATRFTIR spectroscopic approaches could highly valuable in the field, where plant health and nutrient status could be assessed rapidly in situ. Here it is shown that these issues can be overcome and that qualitative spectral measurements can be obtained from plant samples. Due to the non-destructive nature of these approaches, they can be applied for a wider range of crop screening investigations, including the efficiency of nutrient uptake, as well as distinguishing nutrient deficiencies presymptomatically. As such, these spectroscopic methods may be implemented to unearth further details regarding nutrient use efficiency during crop production.

This thesis looks at the role of wild pollinators in providing services to crops. Two data chapters (2 and 3) are accompanied by a modelling chapter (4) which build on the findings of the field studies. The thesis ends with an overview of the trends in pollinator populations and how these relate to the needs of farmers in the UK (chap-ter 5). It is often assumed that commercial pollinators are appropriate substitutes of wild pollinators on farms; however this view neglects the differing roles that particular pollinator taxa might play in providing pollination services. For example, crops with a long growing system may require multiple pollinators to ensure pollination throughout the season. Strawberries in Scotland have an extremely long growing season, flowering from April to August. Chapter 2 presents a study showing season-al complementarity between different pollinating taxa across strawberry farms in Scotland. Pollinators of strawberries also differed in their responses to weather pa-rameters indicating that preserving multiple pollinator taxa could ensure yields un-der different weather scenarios. The requirements of a long-growing season and ad-verse weather may be specific to strawberry production in Scotland, but the valua-tion of multiple taxa can be generalised to systems with differing needs, and also to different ecosystem services. Wild bees are not only valuable for providing complementary services to commercial pollinators, but are also valuable in the longer term as it is unknown whether com-mercial pollinators will be available in the future. There are threats to the supply of honeybees which have already triggered price rises; such supply shocks could force farmers to leave production or to seek other ways of providing pollination, including supporting wild pollinators. However farm management pressures, in particular pes-ticide use, could threaten the ability of wild pollinators to continue to support crop production. The interplay of pesticides and pollination is discussed in chapter 3 and 4. Chapter 3 presents an experiment undertaken on soft-fruit farms which had and had not used the neonicotinoid, thiacloprid, and shows that nests exposed to thia-cloprid had higher worker mortality, and lower male production than those at con-trol farms. This has implications both for pollination services now, as worker mor-tality will reduce the number of bees visiting farms, and also for the maintenance of future pollination services through decreased reproductive capacity of exposed nests. Chapter 4 uses a theoretical model to link pesticide use and habitat use to pollina-tion services, and shows that the use of commercial pollinators could mask the de-cline in wild populations, making local extinctions more likely. Chapter 5 sets out the status and extent of pollinators in the UK, along with popu-lation trends, trends in habitat and trends in pesticide use to provide an overview of how well pollination services are likely to meet the ongoing needs of crop farmers.

Some aspects of the presence of systemic endophytic fungi in agriculturally important New Zealand grasses were studied in relation to plant breeding. Seedling resistance to adult Argentine stem weevil feeding in perennial ryegrass, Italian ryegrass and tall fescue was found to be related to the presence of their respective Acremonium endophytes in the seed rather than to plant genetic resistance. In addition a study of perennial ryegrass revealed that this resistance was independent of endophyte viability. The seedling resistance conferred by the endophyte of Italian ryegrass was found to be beneficial for field establishment. This endophyte differs from that in perennial ryegrass and tall fescue in that it does not confer resistance to Argentine stem weevil on mature plants, but only on seedlings. The extent of plant genetic seedling tolerance to adult Argentine stem weevil feeding was limited to broad inter-specific differences, with tall fescue more tolerant than perennial ryegrass and both of these more tolerant than Italian ryegrass. This ranking corresponds with previous observations on feeding preference on mature plants. A study of factors affecting the concentration of endophyte mycelia in infected seed of perennial ryegrass revealed that plant genetic factors had little effect. The major factors studied were: 1) the endophyte concentration in the maternal parent plant directly influenced the endophyte concentration in the seed. 2) nitrogen fertilizer applications to a seed crop reduced the concentration of mycelia in the seed, with earlier applications having a greater effect. 3) application of the fungicide propiconazole (Tilt) to a seed crop reduced the endophyte concentration in the seed. 4) the endophyte concentration in the seed was found to directly influence the endophyte concentration in seedlings, six month old plants and that of seed harvested from a first year seed crop. As there have been no previous reports of tetraploid perennial ryegrass cultivars with endophyte an experiment was conducted to determine if these could be developed by the standard procedure of colchicine treatment. The results revealed that endophyte was retained following colchicine treatment.

This study investigated commensal feeding interactions between the European harvestman (P. opilio L.) and the predatory mites Balaustium spp. and Anystis baccarum L. It also investigated the feeding behaviour of P. opilio. Experiments were conducted in the laboratory using standardised temperature, humidity, photoperiod and experimental arenas, with eggs of the brown blowfly (Calliphora stygia F.) as prey facsimiles. Due to initial difficulties in obtaining enough predatory mites, mite feeding was manually simulated piercing blowfly eggs with a minuten pin. P. opilio consumed significantly more freeze-killed than live blowfly eggs, indicating that freezing induced chemical and/or physical changes to blowfly eggs that are detected by P. opilio. Significantly more manually pierced eggs were consumed by P. opilio compared with unpierced ones, demonstrating that piercing caused a chemical and/or physical to the egg and increased the feeding rates of P. opilio. Different densities of eggs had no effect on the numbers eaten by P. opilio and placing single pierced eggs next to groups of unpierced eggs also had no effect on the numbers of unpierced eggs eaten. These results suggest that P. opilio does not exhibit klinokinesis or orthokinesis to intensify its search for prey around the area where previous prey were located. P. opilio ate significantly more brown blowfly eggs that had previously been fed on by mites, demonstrating that a short term commensal interaction existed. However, further work is required to demonstrate if the relationship is commensal in the longer term. A comparison between hand-pierced and mite-pierced eggs showed that P. opilio ate significantly more of the former indicating that mite and hand piercing were quantitatively different. The potential for, and importance of, other commensal or mutual relationships between predators in agroecosystems is discussed. The lack of klinokinesis and orthokinesis in P. opilio is compared with other predators and parasitoids that do exhibit these behaviours. The means by which prey are detected by P. opilio are discussed in relation to interpreting behaviours such as prey inspection. Concerns about the effect of pre-treatment and handling of sentinel prey and the problems of using prey facsimiles are raised.

A field experiment was conducted to examine the responses in growth, total dry matter (TDM), seed yield and nitrogen (N) accumulation of Kabuli chickpea cv. Principe and narrow-leafed lupin cv. Fest to different irrigation levels and N fertilizer on a Templeton silt loam soil at Lincoln University, Canterbury, New Zealand in 2007/08. The irrigation and fertilizer treatments were double full irrigation, full irrigation, half irrigation and nil irrigation and a control, full irrigation plus 150 kg N ha⁻¹. There was a 51 % increase in the weighed mean absolute growth rate (WMAGR) by full irrigation over no irrigation. The maximum growth rates (MGR) followed a similar response. The growth rates were not significantly decreased by double irrigation. Further, N fertilizer did not significantly improve crop growth rates. With full irrigation MGRs were 27.6 and 34.1 g m⁻² day⁻¹ for Kabuli chickpea and narrow-leafed lupin, respectively. Seed yields of fully-irrigated crops were trebled over the nil irrigation treatment. With full irrigation, seed yield of chickpea was 326 and that of lupin was 581 g m⁻². Seed yield of the two legumes was reduced by 45 % with double irrigation compared with full irrigation. Nitrogen fertilizer did not increase seed yields in either legume. Increased seed yield with full irrigation was related to increased DM, and crop growth rates, seeds pod⁻¹ and seeds m⁻². Crop harvest index (CHI) was significantly (P < 0.05) increased by irrigation and was related to seed yield only in narrow-leafed lupin. With full irrigation, the crops intercepted more than 95 % of incoming incident radiation at leaf area indices (LAIs), 2.9 and 3 or greater in Kabuli chickpea and narrow-leafed lupin, respectively. In contrast, without irrigation the two legumes achieved a maximum fraction of radiation intercepted of less than 90 %. With full irrigation, total intercepted photosynthetically active radiation (PAR) was increased by 28 % and 33 % over no irrigation for Kabuli chickpea and narrow-leafed lupin, respectively. Fully-irrigated Kabuli chickpea intercepted a total amount of PAR of 807 MJ m⁻² and fully-irrigated narrow-leafed lupin intercepted 1,042 MJ m⁻². Accumulated DM was strongly related to accumulated intercepted PAR (R² ≥ 0.96**). The final RUE was significantly (P < 0.001) increased by irrigation. With full irrigation the final RUE of Kabuli chickpea was 1.49 g DM MJ⁻¹ PAR and that of narrow-leafed lupin was 2.17 g DM MJ⁻¹ PAR. Total N accumulation of Kabuli chickpea was not significantly affected by irrigation level. Kabuli chickpea total N was increased by 90 % by N fertilizer compared to fully-irrigated Kabuli chickpea which produced 17.7 g N m⁻². In contrast, total N accumulated in narrow-leafed lupin was not increased by N fertilizer but was decreased by 75 % with no irrigation and by 25 % with double irrigation (water logging) compared to full irrigation with a total N of 45.9 g m⁻². Total N was highly significantly related to TDM (R² = 0.78** for Kabuli chickpea and R² = 0.99** for narrow-leafed lupin). Nitrogen accumulation efficiency (NAE) of narrow-leafed lupin was not affected by irrigation or by N fertilizer. However, the NAE of Kabuli chickpea ranged from 0.013 (full irrigation) to 0.020 (no irrigation) and 0.017 g N g⁻¹ DM (full irrigation with N fertilizer). The N harvest index (NHI) was not affected by irrigation, N fertilizer or legume species. The NHI of Kabuli chickpea was 0.50 and that of narrow-leafed lupin was 0.51. The NHI was significantly (r ≥ 0.95 **) related to CHI.

A metapopulation is defined as a set of potential local populations among which dispersal may occur. Metapopulation theory has grown rapidly in recent years, but much has focused on the mathematical properties of metapopulations rather than their relevance to real systems. Indeed, barring some notable exceptions, metapopulation theory remains largely untested in the field. This thesis investigates the importance of metapopulation structure in the ‘real world’, firstly by building additional realism into metapopulation models, and secondly through a 3-year field study of a real metapopulation system. The modelling analyses include discrete-and continuous-time models, and cover single species, host-parasitoid, and disease-host systems, with and without stochasticity. In all cases, metapopulation structure enhanced species persistence in time, and often allowed long-term continuance of otherwise non-persistent interactions. Spatial heterogeneity and patterning was evident whenever local populations were stochastic or deterministically unstable in isolation. In metapopulations, the latter case often gave rise to self-organising spatial patterns. These were composed of spiral wave fronts (or ‘arcs of infection’ in disease models) of different sizes, and were related to the stability characteristics of local populations as well as the dispersal rates. There was no evidence for self-organising spatial patterns in the host-parasitoid system studied in the field (the weevil Sitona discoideus and its braconid parasitoid Microctonus aethiopoides), and a new model for the interaction suggested that this is probably due to the strong host density-dependence and stabilising parasitism acting on local populations. Dispersal may be important because of very high mortality in dispersing weevils, which may be related to the scarcity of their host plant in the landscape. If this is the case, the model suggested that local weevil density may be sensitive to the area of crop grown. Stochastic models showed that species in suitably large metapopulations may persist for very long times at relatively low overall density and with very low incidence of density-dependence. This suggests that metapopulation processes may explain a general inability to detect density-dependence in many real populations, and may also play an important part in the persistence of rare species. For host-parasitoid metapopulation models, persistence often depended on the way in which they were initialised. Initial conditions corresponding to a biological control release were the least likely to persist, and the maximum host suppression observed in this case was 84%, as compared with 60% for the corresponding non-spatial models and >90% often observed in the field. Metapopulation structure also allowed persistence of ‘boom-bust’ disease models, although the dynamics of these were particularly dependent on assumptions about what happens to disease classes at very low densities. Models assuming infinitely divisible units of density, models incorporating a non-zero extinction threshold, and individual-based models all gave differing results in terms of disease persistence and rate of spatial spread. Fitting models to overall metapopulation dynamics often gave misleading results in terms of underlying local dynamics, emphasising the need to sample real populations at an appropriate scale when seeking to understand their behaviour.

This study consisted of two sheep grazed dryland pasture experiments. Experiment l compared sheep production from 3-year-old cocksfoot based pastures grown in combination with white, Caucasian, subterranean or balansa clover with a ryegrass-white clover pasture and a pure lucerne forage. Sheep liveweight gain per head from each pasture treatment and the pure lucerne stand was recorded in the 2006/07 and 2007/08 seasons. The cocksfoot-subterranean clover pasture provided equal (381 kg LW/ha in 2006) or higher (476 kg LW/ha in 2007) animal production in spring and gave the highest total animal production (646 kg LW/ha) averaged across years of the five grass based pastures. However, total annual liveweight production from lucerne was higher than any grass based pasture mainly due to superior animal production during summer when lucerne provided 42-85% higher animal production than any of the grass based pastures. In Experiment 2, the effect of stocking rate (8.3 (low) and 13.9 (high) ewes + twin lambs/ha) and time of closing in spring on lamb liveweight gain, pasture production and subterranean clover seedling populations was monitored over 2 years for a dryland cocksfoot-subterranean clover and ryegrass-subterranean clover pasture in Canterbury. In both years, twin lambs grew faster (g/head/d) in spring at low (327; 385) than high (253; 285) stocking rate but total liveweight gain/ha (kg/ha/d) was greater at high (7.26; 7.91) than low (5.43; 6.38) stocking rate. Ewes also gained 0.5 and 1.5 kg/head at the low stocking rate in 2006 and 2007 respectively but lost 0.2 kg/head in 2006 and gained 0.3 kg/head at high stocking rate in 2007. Mean subterranean clover seedling populations (per m²) measured in autumn after grazing treatments in the first spring were similar at both low (2850) and high (2500) stocking rate but declined with later closing dates in spring (3850, 2950, 2100 and 1700 at 2, 4, 6, 8 weeks after first visible flower). Seedling populations measured in autumn after grazing treatments in the second spring were also unaffected by stocking rate (low 1290, high 1190) but declined with later closing dates in spring (1470, 1320 and 940 at 3, 5 and 8 weeks after first flowering, respectively). The effect of stocking rate and closing dates in spring on pasture and clover production in the following autumn was similar to the effects on seedling numbers in both years. However, clover production in the following spring was unaffected by stocking rate or closing date in the previous year at the relatively high seedling populations generated by the treatments. This was presumably due to runner growth compensating for lower plant populations in pastures that were closed later in spring. Subterranean clover runner growth in spring may not compensate in a similar manner if seedling numbers in autumn fall below 500/m². Mean annual dry matter production from cocksfoot and ryegrass pastures grown with and without annual clovers pasture production ranged from 6.4 to 12.4 t DM/ha/y but stocking rate (8.3 vs. 13.9 ewes/ha) during spring did not affect annual pasture production. Pastures overdrilled with annual clovers yielded 23-45% more dry matter production than pastures grown without annual clovers. The study confirms the important role of subterranean clover in improving pasture production and liveweight gains of sheep in dryland cocksfoot and ryegrass pastures. Lowering stocking rate from 13.9 to 8.3 ewes/ha was a less effective method of increasing seed production of subterranean clover in dryland pastures although it did lead to increased liveweight gain per head.

The use of nitrogen (N) fertilizer is generally restricted on mixed species forage systems due to its stimulatory effect on grasses which increases competition with legume species. Reduced legume growth from this competition can compromise forage nutritive value and prospective yields. The controlled-release nature of several enhanced efficiency fertilizer N products holds the potential to improve legume persistence in mixed species pastures while providing supplemental N required by the grass component. The studies contained in this dissertation evaluated the effect of different enhanced efficiency N formulations (ATU, ESN, methylene urea, SuperU, and a 75% ESN: 25% urea blend) and untreated urea on yield, nutritive value, and legume persistence in a ‘Wrangler’ bermudagrass and ‘Durana’ white clover mixture (2014-2016 growing seasons), ‘KY-31’tall fescue and ‘Kenland’ red clover mixture (2015-2016 growing seasons), and ‘KY-31’ stockpiled tall fescue (2015-2017). The three studies were conducted at the University of Kentucky Spindletop Research Farm in Lexington, KY in a randomized complete block design. In the bermudagrass-white clover study, all enhanced efficiency N sources maintained white clover populations similar to the unfertilized grass/clover control, but only ESN caused greater clover composition than standard urea. Total forage yields increased linearly with N rate in all years, but dry weather conditions in the second and third years resulted in lower total yield. Forage nutritive value followed general trends throughout each growing season, but ESN’s ability to maintain clover resulted in higher nutritive value. In the tall fescue-red clover, total forage yields curvilinearly increased with N rate in 2015 but did not vary in 2016. ESN and ESN+urea blend treatments retained clover composition similar to that of the unfertilized control. Stockpiled forage yield increased with higher N rates. Enhanced efficiency N fertilizers with the ability to control N release can enhance forage yield while maintaining clover in mixed species swards.

Els fongs patògens de plantes causen importants pèrdues en les collites, posant en perill la seguretat i qualitat alimentària. Els pèptids antimicrobians (AMPs) mostren una activitat lítica potent i duradora específicament enfront de microorganismes, de manera que tenen un gran potencial com a nous fungicides naturals per al control dels fongs patògens. La seva explotació requereix de sistemes de producció ràpids, eficaços, econòmics i segurs. El principal objectiu d’aquest treball era desenvolupar sistemes de producció sostenibles de AMPs, i la seva caracterització en el control d’infeccions fúngiques per avançar en la seva aplicació en l’agricultura. Les proteïnes antifúngiques (AFPs) secretades per fongs filamentosos són un grup de AMPs rics en cisteïnes, molt estables, actius específicament enfront de fongs. En aquest estudi vam demostrar que les plantes de Nicotiana bentamiana són una excel·lent biofactoria de AFPs mitjançant expressió transitòria usant un nou vector derivat del virus de mosaic del tabac. Utilitzant aquest sistema de producció en plantes, hem produït eficientment dues AFPs molt actives enfront de fongs fitopatògens, la AfpA de Penicillium expansum i la AfpB de Penicillium digitatum. Hem descobert que el compartiment subcel·lular on s’acumulen les AFPs té un impacte important en la producció obtinguda, probablement perquè la seva compartimentació evita la toxicitat cap a les cèl·lules vegetals. Els valors més alts es van obtenir quan les proteïnes es van acumular en els vacúols, aconseguint fins 0,170 mg / g de fulla en el cas de la proteïna més activa AfpA i fins a vuit vegades més per a la AfpB (1,2 mg / g de fulla). També vam demostrar que els extractes crus de plantes que contenen AFP són actius enfront a fongs, sense necessitat de purificar les proteïnes reduint considerablement el processament del material vegetal i els costos de producció. Per tant, el sistema desenvolupat és eficient per a la producció de AFPs, i també és econòmic i segur ja que es basa en plantes. A més, hem desenvolupat un sistema alternatiu per a la producció del pèptid antifúngic PAF102 que prèviament no s’havia pogut produir biotecnològicament. Aquest sistema es basa en acumular el pèptid en les gotes lipídiques (LDs) mitjançant la fusió a una proteïna oleosina de plantes. Mitjançant aquesta estratègia, hem produït PAF102 en llavors d’arròs en quantitats de 20 mg per gram de llavor. No obstant això, la producció en llavors és lenta i per accelerar el procés hem transferit la tecnologia de la fusió a oleosinas de plantes al sistema de Pichia pastoris. Usant aquest nou sistema hem obtingut rendiments comercialment rellevants amb produccions de 180 mg / l de cultiu en només 4 dies. L’acumulació de PAF102 a les LDs de les llavors d’arròs i del llevat facilita enormement la seva extracció per simple flotació en solucions denses, permetent la recuperació de pèptid biològicament actiu. Finalment, hem demostrat que tant AfpA i AfpB produïdes en plantes, com els extractes de plantes enriquits en aquestes proteines, són eficaços en la prevenció d’infeccions fúngiques en cultius econòmicament rellevants, com ara la podridura grisa causada per Botrytis cinerea en fulles i fruits de tomàquet, la piriculariosis causada per Magnaporthe oryzae, o les infeccions de les llavors d’arròs per Fusarium proliferatum. Els nostres resultats proporcionen un sistema de producció sostenible de AFPs i demostren la seva eficàcia en la protecció de les plantes contra les infeccions fúngiques, donant ferm suport per al seu ús com a “fungicides verds” eficaços i respectuosos amb el medi ambient en la protecció de cultius, mentres són al canmp o durant el periode postcollita.
Los hongos patógenos de plantas causan importantes pérdidas en las cosechas, poniendo en peligro la seguridad y calidad alimentaria. Los péptidos antimicrobianos (AMPs) muestran una actividad lítica potente y duradera específicamente frente a microorganismos, por lo que tienen un gran potencial como nuevos fungicidas naturales para el control de los hongos patógenos. Su explotación requiere de sistemas de producción rápidos, eficaces, económicos y seguros. El principal objetivo de este trabajo era desarrollar sistemas de producción sostenibles de AMPs, y su caracterización en el control de infecciones fúngicas para avanzar en su aplicación en la agricultura. Las proteínas antifúngicas (AFPs) secretadas por hongos filamentosos son un grupo de AMPs ricos en cisteínas, muy estables, activos específicamente frente a hongos. En este estudio demostramos que las plantas de Nicotiana bentamiana son una excelente biofactoría de AFPs mediante expresión transitoria usando un nuevo vector derivado del virus de mosaico del tabaco. Utilizando este sistema de producción en plantas, hemos producido eficientemente dos AFPs muy activas frente a hongos fitopatógenos, la AfpA de Penicillium expansum y la AfpB de Penicillium digitatum. Hemos descubierto que el compartimento subcelular donde se acumulan las AFPs tiene un impacto importante en la producción obtenida, probablemente porque su compartimentalización evita la toxicidad hacia las células vegetales. Los valores más altos se obtuvieron cuando las proteínas se acumularon en las vacuolas, alcanzando hasta 0,170 mg/g de hoja en el caso de la proteína más activa AfpA y hasta ocho veces más para la AfpB (1,2 mg/g de hoja). También demostramos que los extractos crudos de plantas que contienen AFP son activos frente a hongos, sin necesidad de purificar las proteínas reduciendo considerablemente el procesamiento del material vegetal y los costes de producción. Por lo tanto, el sistema desarrollado es eficiente para la producción de AFPs, y también es económico y seguro ya que se basa en plantas. Además, hemos desarrollado un sistema alternativo para la producción del péptido antifúngico PAF102 que previament no había podido producirse biotecnológicamente. Este sistema se basa en acumular el péptido en las gotas lipídicas (LDs) mediante la fusión a una proteína oleosina de plantas. Mediante esta estrategia, hemos producido PAF102 en semillas de arroz en cantidades de 20 mg por gramo de semilla. Sin embargo, la producción en semillas es lenta y para acelerar el proceso hemos transferido la tecnología de la fusión a oleosinas de plantas al sistema de Pichia pastoris. Usando este nuevo sistema hemos obtenido rendimientos comercialmente relevantes con producciones de 180 mg/l de cultivo en sólo 4 días. La acumulación de PAF102 en las LDs de las semillas de arroz y de la levadura facilita enormemente su extracción por simple flotación en soluciones densas, permitiendo la recuperación de péptido activo frente a hongos patógenos. Finalmente, hemos demostrado que tanto AfpA y AfpB producidas en plantas, como los extractos de plantas enriquecidos estas proteinas, son eficaces en la prevención de infecciones fúngicas en cultivos económicamente relevantes, tales como la podredumbre gris causada por Botrytis cinerea en hojas y frutos de tomate, el quemado del arroz causado por Magnaporthe oryzae, o las infecciones de las semillas de arroz por Fusarium proliferatum. Nuestros resultados proporcionan un sistema de producción sostenible de AFPs y demuestran su eficacia en la protección de las plantas contra las infecciones fúngicas, apoyando firmemente su uso como "fungicidas verdes" eficaces y respetuosos con el medio ambiente en la protección de cultivos y postcosecha.
Plant diseases caused by pathogenic fungi are responsible of important crop losses endangering food security and safety. Antimicrobial peptides (AMPs), exhibiting potent and durable lytic activity specifically against microorganisms, have a great potential as novel natural fungicides for the control of pathogenic fungi. However, viable exploitation of AMPs requires fast, cost-efficient, and safe production systems. The main goal of this work was to develop a sustainable platform for the production of bioactive AMPs, and to characterize them in the control of fungal infections in plants to advance in their application in agriculture. Antifungal proteins (AFPs) secreted by filamentous fungi are a group of highly stable cysteine-rich AMPs that specifically target fungal cells. In this study, we demonstrate that Nicotiana benthamiana plants are an excellent biofactory for producing AFPs through transient expression using a new vector derived from the tobacco mosaic virus. Using this plant-based production system we efficiently produced two different bioactive AFPs, the Penicillium expansum AfpA and Penicillium digitatum AfpB. We found that the subcellular compartment where AFPs are accumulated has an important impact on protein yield, probably avoiding toxicity towards plant cells. The highest yields were achieved when targeting AFPs to vacuoles, reaching up to 0.170 mg/g of fresh leaves of the highly active AfpA and eight times more of AfpB (1.2 mg/g of leaf). We also show that plant crude extracts containing AFPs are fully active against plant pathogens without requiring further protein purification, thus reducing significantly downstream processing. Therefore, the developed system is efficient for the production of AFPs, and also it is economic and safe since it is based on plants. We also developed an alternative system for the production of the linear PAF102 antifungal peptide that was recalcitrant to be produced in biological systems. This system is based on targeting the peptide to lipid droplets (LDs) through the fusion to a plant oleosin protein. Using this oleosin fusion technology, we produced PAF102 in rice seed LDs, reaching moderate yields of about 20 mg of peptide per gram of grain. Production on rice seeds is long process in order to speed the process, we successfully transferred the plant oleosin fusion technology to the Pichia pastoris system. We produced commercially relevant yields of PAF102 in these yeast LDs, reaching values of 180 mg/l of culture in only 4 days. The accumulation of PAF102 in the LDs of rice seeds and yeast facilitated its downstream extraction and recovery by simple flotation on dense solutions, with the recovered PAF102 being biologically active against pathogenic fungi. Finally, we demonstrate that in planta produced AfpA and AfpB, either purified protein or protein extracts enriched with these two proteins, are efficient in controlling important fungal diseases on economically relevant crops, including Botrytis gray mold disease in tomato leaves and fruits, blast disease in rice plants and Fusarium proliferatum infection in rice seeds. Our results provide a sustainable production system of AFPs, and evidence their efficacy on protecting plants from fungal infection, strongly supporting the use of AFPs as environmental friendly and effective “green fungicides” in crop and postharvest protection.
Universitat Autònoma de Barcelona. Programa de Doctorat en Biologia i Biotecnologia Vegetal

Chinese water chestnut (Eleocharis dulcis (Burm. f.) Trin. ex Henschel) is a new aquatic vegetable to Australia. Lack of research on this crop greatly limits the understanding of its production performance. Therefore, studies on several aspects of this crop were undertaken to provide a scientific basis for improvement in yield and quality.

Firstly, the genetic relationship of Chinese water chestnuts growing in Australia was assessed by using random amplified polymorphic DNAs (RAPDs). For the genetic

analysis of wild putative E. dulcis, three primers separated the samples from 9 out of 10 sites into two distinct groups: E. dulcis and E. sphacelata. In the genetic analysis of samples from cultivated E. dulcis plants, 96 RAPD markers generated by 14 primers separated the samples from Taiwan (var. Shu-Lin), Hangzhou, China (cv. Da Hong Bao), New South Wales, Australia (unknown variety) and the USA (unknown variety) from the rest of the samples from Australia. The remaining samples were too closely related (0.74-4.4% dissimilarity) to be differentiated.

Secondly, the possibility to extend availability of fresh Chinese water chestnut corms by physiological manipulation (photoperiod control) was evaluated in four

photoperiod experiments. When measured, above -ground growth and dry matter production of the whole plants were not significantly affected by photoperiods (8-24 h). However, corm formation was strongly retarded by long days and promoted by the photoperiod which was shorter than a critical value. Under shorter days, significantly more dry matter was shifted towards corms as well as rhizomes, an

effect that became more pronounced as the period of treatment was lengthened.

Thirdly, Chinese water chestnut production in relation to harvest date and cold storage of 'seed' corms was investigated in two experiments. In the first experiment,

March -planted plants were harvested from July to September. Mature corms from each harvest were subsequently stored at 4°C. In terms of corm formation and

maturation as well as soluble sugar concentration in mature corms, the harvests in August were more favorable. After storage at 4°C for 86 d (harvest on 24 September)

to 159 d (harvest on 15 July), no sign of rot nor flesh deterioration was observed. Loss of fresh weight ranged from 0.46% to 6% with the lower value associated with

the shorter storage duration. Corm germination was also favored by shorter storage period. The highest values for the number of sprouts and stems per viable corm and

the length of the longest stem per viable corm were obtained from the harvests on 29  July (139 d storage), 13 August (130 d storage) and 27 August (116 d storage)

respectively. In the second experiment, corms harvested on different dates over the period July to November were stored at 4°C for four different periods prior to planting. Both harvest date and cold -storage duration exhibited significant influence on soluble solid content (°Brix) with the highest values for the first harvest and no cold storage, although the average °Brix value was low for all treatments. Harvest

date and cold -storage duration also showed significant effects on corm sprouting performance evaluated as the number of sprouts and stems, and the length of the

longest stem per viable corm. Average yield per plant showed little difference across `seed' corm harvest dates with the exception of the last. The fresh weight of individual corms was significantly affected by 'seed' corm harvest date but not by storage duration.

Fourthly, the possibility of Chinese water chestnut in vitro culture was investigated with several different explants and culture media. Among all the explants examined, only young rhizome nodes and tips, dormant buds and corm skin with bud scars (buds removed) responded to in vitro culture by the production of shoots or shoot clusters. Root initiation was readily stimulated in the derived microshoots. The test

tube plantlets were successfully transferred to the screenhouse, and their subsequent performance compared favorably with that of corm -derived plants. 

Lastly, a putative Chinese water chestnut disease, tip yellowing and brown stem lesions, which was observed in the greenhouse and in the field, was studied. As no

corresponding symptoms showed up when healthy plants were inoculated with spores derived from the isolates obtained from affected tissue, a nutritional disorder,

perhaps potassium deficiency, was therefore suggested to have been responsible for the symptoms.

Instrument criteria, in terms of wavelength range, wavelength resolution, signal to noise ratio, sensitivity and illumination/detector were defined for the use of near infrared (NIR) spectroscopy in the assessment of soluble solids content (SSC) in intact fruit in an in-line system. Techniques for predictive model generation and transfer of predictive models across a number of systems were assessed in tenns of root mean squared error of prediction (RMSEP). A comparative study of components making up an NIR spectroscopic system established that for the application of assessment of SSC in intact fruit, quartz halogen light sources could provide adequate low cost radiant energy and prisms could provide cheap, more efficient dispersion and higher throughput than flat diffraction gratings. Three wavelength dispersion elements (single equilateral prism, two prisms in series and a ruled diffraction grating) were separately assessed. Calibration perfonnance for sucrose in a water-cellulose matrix was significantly degraded by a signal to noise ratio (SNR) <5000: 1, and when wavelengthresolution was decreased beyond a FWHM of 16 nm (at 912 nm). Therefore either photo- diode arrays or binned charge-coupled devices could be used as photodetecting elements if SNR is maintained above this level. A body-transmittance optical path was preferred over reflectance optics to eliminate the 'noise' from specularly reflected light. However, physicaly contacting the fruit with an optical barrier to separate illuminated and detected regions constrained process rates. Therefore, an illumination/detector configuration was designed to allow rapid, non-contact spectral measurements to be made. This configuration supported comparable calibration statistics for assessment of SSC of intact melons as a 'contact' configuration (e.g. root mean squared error of cross validation (RMSECV) of 0.740 and 0.650 Brix non-contact and contact, respectively). Predictive models developed using partial least squares (PLS) regression were significantly more accurate than those developed using multiple linear regression, principal component regression or parallel regression. Wavelength selection techniques were examined. Predictive PLS models based on knowledge of spectrally important wavelengths (for SSC, 630 to 1040 nm) were superior to models based on other wavelength selection techniques. Assessment of data pre-treatment techniques showed that, in most cases, mean centred and autoscaled absorbance data provided the best results. Nine methods for transfer of calibration between instruments were compared against the performance of a simple model updating (MU) technique. While MU gave consistently better predictions on slave instruments, this approach requires maintenance of calibrations on every instrument. Of the established standardisation methods, direct standardisation of the wavelet coefficients was the most efficient. These design criteria were used in the construction of a prototype fruit sorting system, with performance assessed over a period of two years. The hardware components of this system proved adequately robust to endure the rigours of a pack-house environment and the accuracy of the sorting achieved an RMSEP of 11 0.7° Brix (standard deviation and range of sse in sample set, 1.5° and 8.5°, respectively). 111

Accurate predictions of the timing of harvest and crop yield are of major benefit to large scale commercial tomato growers as they support efficient utilisation of resources and enable planting schedules to be managed so that there is a regular supply of product to the market. The predictive tools available to field tomato growers are limited as most tomato crop models have been developed for greenhouse conditions and indeterminate tomato cultivars. As the success of a crop yield forecasting system strongly depends on the crop simulation models ability to quantify the influence of weather and management practices on plant development, data describing effects of these factors on the key developmental events of flowering and fruit maturity are valuable. In this study the effects of a range of management factors and planting times on flowering and fruit maturation were assessed in field trials and commercial crops. Analysis of commercial crop data from 217 crops grown over three production seasons in the Bundaberg region in Queensland, Australia demonstrated the dominant effect of temperature on crop development and also identified differences in developmental rate due to soil type. Replicated field trials revealed a small but significant effect of crop pruning strategies on flowering time and harvest date. Varying the fruit load on plants pruned to produce different branching patterns induced no significant changes in the photosynthesis rate of the plants, indicating that plasticity in source sink relations exist with new shoots from the axils of the leaves replacing fruit as the major sink in plants with reduced fruit load. It was also observed that varying the branching patterns in field grown tomato had a significant impact on assimilate partitioning and that this response resulted in a significant branching pattern effect on harvesting date of the crops. The fruit maturation rate and first harvesting time of commercial field grown tomato was influenced by pruning strategy, with the optimum strategy being that which maintained a desired source-sink ratio of vegetative and reproductive sink organs for optimum yield of the crops. Base thermal time and seasonal pattern models for prediction of harvest date were developed that provided improved predictability over the current calendar date model used by industry. No adequate prediction of yield was achieved, and much more work is needed in identification of the key factors causing the very large crop to crop differences in yield in commercial production in the study location.

Project aims to evaluate the pollination biology of C. papaya in regards to anemophily, entomophily and agamospermy. The variation in seasonal fruit set typical of subtropical climates is also investigated. The research aims to improve crop management strategies.. Papaws are one of the most significant fruits in central Queensland, yet there are specific problems associated with consistent fruit production in this subtropical region. This is the first time that a comprehensive analysis into the pollination mechanism of papaw has been conducted, in a country other than that of its origin. Additionally, research into factors influencing fruit set and seed set under subtropical climates has been performed. Earlier studies on the pollination biology of C. papaya have suggested that pollen transfer is wind and/or insect mediated. Whilst papaws grown in Australia are believed to be wind-pollinated, a diverse number of insect species have been proposed to fulfil pollinator function in other areas of cultivation, which reflects that the pollination mechanism in papaw is unknown. Contrary to all previously published research in the area, pollination of C. papaya is carried out by hawkmoths (Lepidoptera: Sphingidae). Seven pollinator species and a further four suspected pollinator species have been identified for the central Queensland region. All species belong to the same subfamily, the Macroglossinae. Contrary to anecdotes from growers, neither native or European bees, nor wind was of significance in the pollination of dioecious papaw cultivars and incidences of apomictic and parthenocarpic fruit set occurred though were rare. Sphingid pollinators showed marked patterns of seasonal occurrence. Weekly observations and light trap results conducted over two years in the vicinity of Rockhampton, indicated that adult sphingids were absent from the central Queensland region during winter from the middle of June until the middle of August. Their absence correlated with relatively low average weekly minimum temperatures of 10.4 °C and below. Overwintering of sphingids in the pupa stage in order to overcome adverse climatic effects7 was observed for two species. Seasonally occurring fruit set and periods of low seed set of C. papaya, under the subtropical central Queensland climate were due to three key factors - the availability and viability of pollen and the absence of sphingid pollinators. The overall stagnation of tree growth including a decrease in open flower numbers during winter also played a role. Individual papaw lines (particularly Hybrid 29) showed better adaptations to heat and cold stress in respect to pollen quantity and viability. Seed set, irrespective of viability status, increaSea fruit size by an average of 0.89 g/seed. The pollination mechanism by which nectarless pistillate flowers attract pollinator visitation has been identified and involves a multitude of stimuli, including those of olfaction, gustation, tactility and vision. Petals of both flower types show the same visual properties, of absorbing wavelengths of the UV-spectrum (<405 nm), selectively reflecting only those of longer wavelengths. Additionally, pattern fanning trichomes attached to scent glands are present on both pistillate and staminate C. papaya flowers. Mechanosensory receptors on the sphingids probosces exactly match trichome patterns and the presence of contact chemoreceptors suggests their involvement for foodsource recognition.. The results of this study provide an information base which can now be integrated into new horticultural practices with regard to pollination requirements of papaw grown under subtropical climates. In particular seasonal trends of pollinator abundance, pollen quantity and pollen viability could translate directly into strategies for improving fruit yield. Plantings of larval host plants in vicinity to papaw orchards could provide the frrst step towards the management of hawkmoth pollinators. The existence of apomictic seed formation in papaw establishes a basis for further studies concerning sex determination prior to anthesis (as it is only possible at this point of time), making use of the effects of heterosis yet circumventing the constant breeding programmes providing the Fl-crosses.. Further investigations into varietal differences of pollen quality and quantity during the subtropical growing season as well as the influence of seedlike structures on fruit set and flesh thickness may also prove useful in the selection of more suitable papaw cultivars grown under subtropical climates. Apart from objectives focusing on the fruit production of papaw, results obtained on the mechanisms of pollinator constancy, in particular the sensory recognition of floral parts by hawkmoth pollinators, offer a far more universal approach into plant-pollinator relationships, which presently are known to function by 'deceit'.

"Stevia, a zero calorie natural sweetener, is a new crop for Australia. It was approved in 2008 for use as a food ingredient by Food Standard Australia and New Zealand (FSANZ). Steviol Glycoside (SG) found in the leaves is responsible for the sweetness of Stevia. As a new crop to Australia, commercial cultivation of Stevia is yet to commence. The agronomic requirements of the crop in Australian conditions are yet to be determined. Therefore, the current study aims to lay the foundation for developing both agronomic practice and varietal selection for stevia cultivation in Australia"--Abstract.

Yield decline following continuous cropping cycles in Central Queensland has been attributed to the declining soil nitrogen status. In this study an assessment of the level of nitrogen fixation was made to assist in the selection of potential ley pasture legumes for use in rotational systems to achieve sustainable cropping yields.

Twenty one winter and summer growing legumes were evaluated for nitrogen fixation in glasshouse trials in two seasons. Nitrogen fixation was determined using the hydrogen evolution technique (an instantaneous measure of fixation rate) in an artificial media trial and the 15N natural abundance technique (an integral measure of fixation) in a soil based trial.

Climate is the most significant factor in determining plant growth and productivity (Buchdahl, 1996). Recent studies with general circulation models suggest that one of the consequences of increase in greenhouse gases may be greater variability in the climate of a region. Given the possibility of increased variations in climatic conditions, it is deemed that the study of the relationship between climate and crop yield would be useful. For a system which is too complex to be explained by the laws of physics, typically, the determination of the relationship is done through multiple regression analysis. The latter approach is adopted in this study.

Yields of four crops - wheat, barley, sunflower, and cotton - are related to minimum, maximum, and average values of rainfall, temperature, and humidity at planting time, flowering time, and harvesting time for the Fitzroy catchment region of Central Queensland. The most significant climatic factors affecting crop yield are identified. Regression models have been developed which are capable of forecasting the variability of crop production in the region due to climatic variations. Consistent genetic trends and use of existing management practices are assumed in such forecasting.

Furthermore, the complex interaction of climate on crop growth is addressed through the application of the statistical tool of path analysis. From the application of stepwise multiple regression analysis techniques, three explanatory variables are identified as important for each of wheat and barley yields and only one variable is identified for each of sunflower and cotton yields. The regression models are discussed in Section 5.3 of Chapter V. By using path analysis it is found that additional variables have indirect influence on wheat and barley yields. Multiple regression analysis could not identify these variables, which are significant but in an indirect way. The path diagram models are discussed in Section 5.4 of Chapter V. Path analysis allowed us to explore the existence of important variables with indirect influence, and the technique provided us with greater information in predicting changes in yields from the vagaries of climate than is ordinarily available from econometric and regression models.

Involves study of the grass seed industry in Central Queensland by conducting a market survey to determine the existing mechanisation in the seed industry and the problems faced by farmers. The main aim of the study is the design of an improved, effective grass seed harvester.. This research project sponsored by the Centre for Agricultural Technology(CAT) is seen as assistance to the Agricultural and Beef Industries which are among the major contributing industries to the Australian economy. The project involves a study of the grass seed industry in Central Queensland by conducting a market survey to determine the existing mechanisation in the seed industry and the problems faced by this group of farmers. The main aim of the study was to arrive at a design of an improved and more effective novel grass seed harvester, specifically designed by considering all the characteristics unique to grass seeds and the details which earlier research had indicated would help to increase the quality and the total yield, from the current 40-60% to about 80-95%. Earlier research on an air-assisted brush type of harvester indicated the problem of having to draw the seeds through the fan before separation. This seemed to cause trauma to the seeds which revoked the seed germination capacity. This research work has therefore been focused on designing a seed separator to be located ahead of the fan which could successfully separate the seeds of various shapes and sizes, from the large volume of conveying air required for suction, before entering the fan. A curved duct concentrator and a uniflow cyclone were selected as part of the experimental work and a theoretical approach was developed to understand and define the problems unique to the separation of the grass seeds. The results of tllese experiments and their comparison with the previous existing separators and harvesters have been discussed in this thesis. The technique for fan design for the harvester and finally the design specifications of a self driven harvester and a tractor mounted harvester were developed by incorporating all the harvester units, i.e the header unit, the separator and the fan.

Irrigation of heavy soils can result in temporary anoxic conditions in the rhizosphere. The aeration of the subsurface drip irrigation water was calculated to deliver an amount of oxygen that is significant to root respiration (equivalent to some hours of respiration need). Broadacre cotton (Gossypium hirsutum L.) irrigated with aerated water developed significantly more extensive and heavier (17.3%) root systems, canopies that enabled greater light interception (2.6% ), and produced significantly higher lint yields ( 16%) due to more bolls per plant (15%) in the 05/06 season. The increased yields of aerated plants were associated with improved gross production water use index (GPWUI), irrigation water use index (IWUI) and crop water use index (CWUI) by 16.9, 16.8 and 15.5% respectively. These improvements in yields and water use efficiencies in response to aeration were ascribed to enhanced root development and performance. Although trends were similar across two seasons, the differences were not significantly different in the first (04/05) season, a result attributed to inadequate replication in the trials of that year. A chickpea ( Cicer arietinum L.) crop grown in rotation to cotton produced significantly higher yields (26.9%; 359 vs. 283 g m-2), IWUI (27%, 2400 vs. 1890 g m-3) and GPWUI (26.8%; 1750 vs. 1380 g m-3) under aerated SDI, compared to nonaerated SDI. The aeration effect was more pronounced when drippers were placed at depth (25 and 35 em, compared to 5 and 15 em) (chickpea pot experiment). Aerated chickpea irrigated at the deepest emitter depth produced significantly higher yields (by 1 0.9%) and GPWUI (21 %) than their non-aerated counterparts. A field sorghum (Sorghum bicolor L.) crop grown following the second chickpea crop did not respond to the aeration treatment in terms of yield or water use efficiency (WUE), a result attributable to either the effect of a relatively wet season where the contribution of irrigation to total water use was less than 50%, or to a relative insensitivity of sorghum to soil anoxia. Aeration of SDI water improved cotton plant growth (larger root systems, heavier above-ground biomass and higher yield) for irrigation water with an electrical conductivity of0.78 dSm-1, but not at higher levels. The ratios of cotton leaf K+:Na+, Ca2+:Na+ and Mg2+:Na+ were increased (by 45.7%, 31.7% and 34.9%, respectively) by the aeration treatment, compared to the control, suggesting a higher level of salt exclusion by the root in the aerated treatments. This result is interpreted as due to maintenance of membrane integrity under aerobic conditions. Aeration of SDI has the potential to make a major contribution to sustainable water use for irrigated agriculture on heavy soils. The benefits of aeration of SDI in terms of both crop yield and water use efficiency improve the economic feasibility of this irrigation method.

Project tests the hypothesis that floral induction and flowering time in Sorghum bicolor L. can be "regulated by in-crop canopy modification", with the result that farmers would be better able to manage their corps to avoid severe crop water stress at flowering.

An opportunity exists for Australia to satisfy the expanding Asian fresh produce markets, because of our climate, space and technology to expand and enhance production of fruit and vegetables. Growers always strive to obtain maximum yields of high quality produce from their fields. Many factors such as climate, suitable cultivars, cultivation practices, soil, availability of water and nutrients can influence yields of high quality produce. An important and effective method to reduce costs is to improve productivity while maintaining quality. East Gippsland, the focus of this study, has a significant opportunity and potential for the production of fresh whole and fresh - cut packaged, branded vegetables for the domestic and export markets. The aim of this research was to investigate the effects of current irrigation practices on overall yield and the occurrence of hollow stem in broccoli and to compare the outcomes from different irrigation systems.

Spiders are naturally occurring predators of insects in agroecosystems. The use of broad spectrum pesticides in agriculture is likely to disrupted spider communities and have a negative impact on their role as biocontrollers. The overall abundance, the species richness, diversity and guild structure of spiders in tropical mango orchards in central Queensland were investigated in this study. Experiments were performed to assess the potential of spiders as natural predators to pest insects in mango orchards. The effects of pesticides on the spider communities were assessed to establish the extent to which the communities were disrupted and the extent of recovery from this type of disturbance. The short term (acute) and long term (chronic) effects were investigated. The spiders in unsprayed mango orchards were relatively high in abundance, species richness and species diversity. Spiders were present in significant numbers at all sampling times,both day and at night, and during all seasons. The results suggest that spiders do not capture large numbers of prey. However spider exhibit a diversity of capturing techniques so that they capture a variety of insects. The most common guild was the orb-weavers. The spider abundance and diversity four days after spraying with methidathion suggested that recovery of spider after disruption such as the use of pesticides' occurs quickly. Presumably this recovery occurs due to spiders moving into the orchard from surrounding bush land. The long term use of pesticide does appear to disrupt the community and as evidenced by decreases in the abundance, species richness and diversity of spiders. While it is unlikely that pesticide usage will be eliminated in most commercial mango orchards, this study demonstrates that spiders are potentially important biocontrollers and that they are adversely affected by pesticide use. In the longer term, it will be desirable to develop IPM strategies to minimise pesticide use and maximise the role of spiders as biocontrollers. Such strategies will depend on studies such as this one and extensions of it.