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1
Farhoodi, Alireza. « Lime requirement in acidifying cropping soils in South Australia ». Title page, table of contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phf223.pdf.
Texte intégralRésumé :
"August 2002" Bibliography: leaves 230-254. Field sites and soils from cropping studies in the mid-north of South Australia were used to address questions of soil responses to lime and the influence of acidifying inputs. The study showed that LMWOAs associated with different stubbles can help to ameliorate toxicity through complexation with A1.
2
Thomas, Benjamin Mark. « The role of vesicular-arbuscular mycorrhizal fungi in Linum usitatissimum L. production in Southern Australian soils ». Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pht4541.pdf.
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Bibliography: leaves 106-132. This project investigated the role of VAM fungi in the growth and nutrition of Linum usitatissimum L. in agricultural soils in southern Australia. It had two general aims: (1) to examine the role of indigenous VAM fungi in the growth and nutrition of linseed in field soil collected near Clare, South Australia; and (2) to examine the effect of VAM fungi on the Zn nutrition of Linola.
3
McLaughlin, Michael John. « Phosphorus cycling in soil under wheat-pasture rotations / ». Title page, contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phm1615.pdf.
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4
Wallace, Ashley J. « The effect of environment, soil type and farm system management on nitrogen use efficiency and nitrous oxide emissions from cereal crops in south eastern Australia ». Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232432/1/Ashley_Wallace_Thesis.pdf.
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This thesis outlines findings from a series of field experiments measuring the efficiency with which wheat and barley crops grown in south eastern Australia utilise nitrogen (N) fertiliser, with particular focus on loss of N as emissions of the greenhouse gas: nitrous oxide. N use efficiency varied significantly across regions, seasons and management strategies, while nitrous oxide emissions were highest in high rainfall environments or under irrigation compared with lower rainfall environments. Strategies which match the rate and timing of fertiliser application to crop demand resulted in greater efficiency, offering opportunities to reduce the greenhouse footprint of crop production.
5
Dennis, Jeremy Ian. « Chocolate spot of faba beans in South Australia ». Title page, contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09A/09ad411pdf.pdf.
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Bibliography: leaves 81-100. Entry of inoculum into a crop and disease development in the crop cannot be prevented because spores are airborne and there is a lack of highly resistant varieties. This makes complete control of chocolate spot unlikely. It should however, be possible to improve current levels of disease control through the integration of the factors identified in the study.
6
Taylor, Sharyn Patricia. « The root lesion nematode, Pratylenchus neglectus, in field crops in South Australia ». Title page, contents and summary only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09pht2462.pdf.
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Includes bibliographical references (leaves 241-25). Aims to evaluate sampling procedures; assess the extent and magnitude of yield loss caused by Pratylenchus neglectus; assess the population dynamics of Pratylenchus neglectus in cereals; determine whether resistance occurs in field crops; and, assess whether variation occurs between geographically isolated species of Pratylenchus neglectus
7
Valizadeh, Reza. « Summer nutrition of sheep based on residues of annual crops and medic pastures ». Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phv172.pdf.
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Chen, Juan. « Mobility and environmental fate of norflurazon and haloxyfop-R methyl ester in six viticultural soils of South Australia / ». Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09AEVM/09aevmc518.pdf.
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Fletcher, Cheryl Florence. « Spatial variability of weeds, soils and crops in fields of the south Peace River region, Alberta ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40049.pdf.
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Odeh, Inakwu Ominyi Akots. « Soil pattern recognition in a South Australian subcatchment / ». Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09pho23.pdf.
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Lotfollahi, Mohammad. « The effect of subsoil mineral nitrogen on grain protein concentration of wheat ». Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phl882.pdf.
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Copy of author's previously published work inserted. Bibliography: leaves 147-189. This project examines the uptake of mineral N from the subsoil after anthesis and its effect on grain protein concentration (GPC) of wheat. The overall objective is to examine the importance of subsoil mineral N and to investigate the ability of wheat to take up N from the subsoil late in the season under different conditions of N supply and soil water availability. Greenhouse experiments investigate the importance of subsoil mineral N availability on GPC of wheat and the factors that contribute to the effective utilisation of N. The recovery of N from subsoil, the effect of split N application on GPC and short term N uptake by the wheat at different rooting densities are also studied.
12
Norrish, Shane A., University of Western Sydney, of Science Technology and Environment College et School of Environment and Agriculture. « Soil and water interactions controlling wheat crop response to phosphorus fertiliser in north-western New South Wales ». THESIS_CSTE_EAG_Norrish_S.xml, 2003. http://handle.uws.edu.au:8081/1959.7/613.
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This thesis examines the response to P fertiliser by wheat crops growing in the vertosol soils of the low rainfall areas of the northern grain zone of eastern Australia. Farmers in this region depend on water accumulated from rainfall over a fallow period and stored in the subsoil to increase wheat grain yield beyond that normally achievable from in-crop rainfall and to decrease the production risks due to rainfall variability. The large variability in stored water, seasonal rainfall and subsoil properties result in extremely varied yield and yield responses to P fertiliser between seasons and between sites. Finally, as a practical guide to predicting wheat response to P fertilizer: 1/. current sampling strategies of determining P only in the surface 10 cm appear to be adequate for soils with bicarbonate P concentrations greater than 15 mg/kg. 2/. For soils with lower concentrations in the surface, sampling of 80 cm is recommended. Crops with a mean concentration of bicarbonate P greater than 7 mg/kg between 10 - 80 cm are unlikely to respond to P fertiliser. 3/. No increase in profitable grain yield response was found for fertiliser applications greater than 10 kg P/ha.Doctor of Philosophy (PhD)
13
Isaac, Gura. « Crop rotation and crop residue management effects under no till on the soil quality of two ecotopes in the Eastern Cape, South Africa ». Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2934.
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The degradation of soil quality due to undesirable farming practices has reached alarming scales in the Eastern Cape and this has had negative repercussions on soil productivity and the environment in general. There is growing evidence that conservation agriculture (CA) practices involving minimal mechanical disturbance, maintaining permanent surface cover and embracing diverse crop rotations increase soil organic carbon (SOC) and therefore has potential to mitigate soil quality deterioration. A study was carried out at two sites located in two ecotopes to investigate the effects of crop residue retention and crop rotations in a no till system on overall soil quality using the Soil Management Assessment Framework (SMAF) as the soil quality assessment tool. The CA study trials were laid out in 2012 at two different locations, one at the Phandulwazi Agricultural High school within the Phandulwazi Jozini ecotope and the other one at University of Fort Hare Research Farm within the Alice Jozini ecotope. The experiment was laid out as a split-split plot arrangement in a randomized complete block design with three replicates. Tillage treatments were applied on the main plots while crop rotation treatments were applied as subplots. Crop residue retention treatments were applied as sub-sub plots. The rotational treatments were maize-fallow-maize (MFM), maize-fallow-soybean (MFS), maize-wheat-maize (MWM) and maize-wheat-soybean (MWS). The initial assessment of the overall soil quality of the two ecotopes using the SMAF soil quality index (SQI) revealed that the soils at the Alice site were functioning at 80% while the soils at the Phandulwazi site were functioning at 79 percent of their optimum capacity. The slight difference in the soil quality of the two ecotopes could be attributed to their different soil organic C contents where the Alice Jozini ecotope had significantly higher soil organic C contents than the Phandulwazi Jozini ecotope. After 3 years of continuous treatment application, crop residue retention significantly improved most of the measured soil quality parameters. Generally across the sites, more soil organic C, microbial biomass C (MBC), ß-glucosidase (BG) activity, mineral N, extractable P and K, Cu, Zn, Mn, Fe, and macro-aggregates were recorded in treatments where crop residues were retained. Crop rotations alone did not have a significant impact on most of the measured soil quality indicators. The crop rotations influenced significantly the availability of mineral N across the two sites, highlighting the importance of using a legume in rotations on available N for the subsequent crops. Most of the measured soil attributes were not significantly influenced after 3 years of continuously applying combined treatment of CA components. Mineral N (NO3 + NH4), K, Zn and Fe were significantly impacted on by the interactions of CA components at the Phandulwazi site, while N, Cu, Zn and Mn were significantly increased at the Alice site. Low response of SOC to combined CA treatments in the short-term prompted the need to examine treatment effects on individual soil carbon fractions. The interaction of crop rotation and residue management techniques were significant on the fine particulate organic matter – C fractions and microbially respired C. These soil C fractions were more sensitive to short-term treatments of combined CA components than SOC and MBC, therefore they can be used as short-term indicators of CA effects on SOM. Soil organic carbon, MBC, extractable P and K, soil pH, EC, b, AGS (aggregate stability) and BG activity were measured and the Soil Management Assessment Framework (SMAF) used to calculate soil quality index (SQI) values for each treatment. The combination of the crop rotations with crop residue retention showed the potential to significantly improve SQI values in the long term. The highest soil quality improvement at both sites was achieved by the maize-wheat-soybean (MWS) rotation with crop residue retention.
14
Bagheri, Kazemabad Abdolreza. « Boron tolerance in grain legumes with particular reference to the genetics of boron tolerance in peas ». Title page, summary and contents only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phb144.pdf.
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Sheldon, Bonita Joy. « Heavy metal uptake and accumulation in agricultural crops in urban areas of the Western Cape ». Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/2006.
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Thesis (MTech (Physical Sciences))--Cape Peninsula University of Technology, 2005.A research study into heavy metals in the Cape Town area, found significant amounts of potentially toxic metals such as lead, cadmium, chromium and iron leaching into the underground aquifer. A further additional study conducted on a community garden in Khayelitsha, showed that vegetable crops have the tendency to accumulate certain heavy metals if they are present in soil and water resources. This study was centered around the Philippi Horticultural Area, which is a large significant farming area within the Cape Metropolitan Region. The significance of the study lies in the fact that at least 50% of the local farmers' produce is sold directly to street traders, residents, local supermarket-chains and restaurants. The remainder of the produce is sold at the Epping Market. The purpose of this study was to investigate heavy metal accumulation in various vegetable crop species taken from some of the local farms in the Phillipi Farming area with the objective to: • investigate heavy metal accumulation in various vegetable crop species taken from some local farms in the Phillipi Farming area. • determine the concentrations of heavy metals present in water and soil resource since these will be the primary source of heavy metals to the vegetables. • determine the soil pH and soil organic matter as these two factors would determine the bie-availability ofthe heavy metals. • identify those crops that pose a definite health risk by means of comparing the determined results to the allowed limits.
16
Shrestha, Hari Ram. « Post-fire recovery of carbon and nitrogen in sub-alpine soils of South-eastern Australia / ». Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/6963.
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The forests of south-eastern Australia, having evolved in one of the most fire-prone environments in the world, are characterized by many adaptations to recovery following burning. Thus forest ecosystems are characterized by rapid regenerative capacity, from either seed or re-sprouting, and mechanisms to recover nutrients volatilized, including an abundance of N2 fixing plants in natural assemblages. Soil physical, chemical and biological properties are directly altered during fire due to heating and oxidation of soil organic matter, and after fire due to changes in heat, light and moisture inputs. In natural ecosystems, carbon (C) and nitrogen (N) lost from soil due to fires are recovered through photosynthesis and biological N2 fixation (BNF) by regenerating vegetation and soil microbes.This study investigated post-fire recovery of soil C and N in four structurally different sub-alpine plant communities (grassland, heathland, Snowgum and Alpine ash) of south-eastern Australia which were extensively burnt by landscape-scale fires in 2003. The amount and isotopic concentration of C and N in soils to a depth of 20 cm from Alpine ash forest were assessed five years after fire in 2008 and results were integrated with measurements taken immediately prior to burning (2002) and annually afterwards.
Because the historical data set, comprised of three soil samplings over the years 2002 to 2005, consisted of soil total C and N values which were determined as an adjunct to 13C and 15N isotopic studies, it was necessary to establish the accuracy of these IRMS-derived measurements prior to further analysis of the dataset. Two well-established and robust methods for determining soil C (total C by LECO and oxidizable C by the Walkley-Black method) were compared with the IRMS total C measurement in a one-off sampling to establish equivalence prior to assembling a time-course change in soil C from immediately pre-fire to five years post-fire. The LECO and IRMS dry combustion measurements were essentially the same (r2 >0.99), while soil oxidizable C recovery by the Walkley-Black method (wet digestion) was 68% compared to the LECO/IRMS measurements of total C. Thus the total C measurement derived from the much smaller sample size (approximately 15 mg) combusted during IRMS are equivalent to LECO measurement which require about 150 mg of sample.
Both total C and N in the soil of Alpine ash forests were significantly higher than soils from Snowgum, heathland and grassland communities. The ratio of soil NH4+ to NO3- concentration was greater for Alpine ash forest and Snow gum woodland but both N-fractions were similar for heathland and grassland soils. The abundance of soil 15N and 13C was significantly depleted in Alpine ash but both isotopes were enriched in the heathland compared to the other ecosystems. Abundance of both 15N and 13C increased with soil depth.
The natural abundance of 15N and 13C in the foliage of a subset of non-N2 fixing and N2 fixing plants was measured as a guide to estimate BNF inputs. Foliage N concentration was significantly greater in N2 fixers than non-N2 fixers while C content and 13C abundance were similar in both functional groups. Abundance of 15N was depleted in the N2 fixing species but was not significantly different from the non-N2 fixers to confidently calculate BNF inputs based on the 15N abundance in the leaves.
The total C pool in soil (to 20 cm depth) had not yet returned to the pre-fire levels in 2008 and it was estimated that such levels of C would be reached in another 6-7 years (about 12 years after the fire). The C and N of soil organic matter were significantly enriched in 15N and 13C isotopes after fire and had not returned to the pre-fire levels five years after the fire. It is concluded that the soil organic N pool can recover faster than the total C pool after the fire in the Alpine ash forests.
17
Shi, Xianzhong. « Hyperspectral sensing of acid sulphate soils and their environmental impacts in South Yunderup, Western Australia ». Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/1820.
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Several sources of hyperspectral data were used to map the occurrence and spread of acid sulfate soils (AAS). Surface evolution of mineralogy during controlled oxidation of sulphidic material showed the formation of secondary iron minerals linked to soil pH ranges. Spectral characterization, image classification and PLSR of hyperspectral data successfully mapped the occurrence of surface and subsurface acid conditions and related toxicity by linking mineralogy to pH.
18
George, Suman Jacob. « Effects of land-use change on phosphorus forms in South-West Australian soils ». University of Western Australia. School of Earth and Geographical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0078.
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[Truncated abstract] Eleven sites, each with the trio of land uses: Eucalyptus globulus plantation, pasture and natural vegetation, representing from the Mediterranean climate, high rainfall region (<550 mm annually) of south-western Australia were investigated to assess medium-term changes in the P-supplying capacity of soils in eucalypt plantations growing on agricultural land. The natural vegetation soils were a benchmark for comparing soil P change since land clearing and development for agriculture. The experimental framework provided an ideal basis for studying changes in P forms since land clearing and fertilization for agriculture and the ensuing conversion to plantations (on an average 9 years ago). Conventional soil P indices measure plant available P that is more relevant to short duration annual crops and pastures. To predict medium-term P availability, P forms were determined using Hedley et al.’s (1982) fractionation scheme and fractions were grouped using the Guo and Youst (1998) criteria into readily, moderately and sparingly available P. The P species were also determined by 31P NMR spectroscopy of 0.5M NaOH-0.1M EDTA extracts. Hedley et al.’s (1982) inorganic P extracted by anion exchange resin and by NaHCO3 are widely considered to be approximations to the actual plant available P. The availability to plants of other P fractions is less certain and this is examined in an experiment to compare the plant availability of various P fractions in soils from fertilized and unfertilized land uses following exhaustive cropping in the glasshouse. The soil texture for the sites studied included coarse sand, loamy sand, clayey sand, and sandy loam. Surface soils (0-10 cm) have pH(CaCl2) in the acidic range (mean 4.4) and there is no significant difference due to differences in land use (P<0.05). The soils are of low EC (1:5 H2O) - 6 mS m-1. There is an almost 5-fold variation in organic C among sites (from 1.4% to 8%) but organic C values did not show any significant effect (P<0.05) of changes in land use. To evaluate the degree of similarity of soils within each triplet set at a site principal component analysis was carried out on those soil chemical⁄mineralogical characteristics that were least likely to be affected by changes in land use practices. This analysis showed good matching of the triplet of sub-sites on the whole, especially for the duo of pasture and plantation land uses. This degree of matching of the trio of land uses was considered while interpreting the effects of land use on the forms and behaviour of soil P, and variations due to various extents of mismatch were mostly addressed using statistical techniques including regression analysis to interpret sub-site difference
19
Firth, Hamish. « Development of a financial model to examine the financial viability of Mallee Eucalyptus crops in South Western Australia ». Thesis, Firth, Hamish (2019) Development of a financial model to examine the financial viability of Mallee Eucalyptus crops in South Western Australia. Masters by Coursework thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/50274/.
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In the current state of environmental change being experienced by the world, businesses and governments are looking for renewable resources which can be used to produce the products which are currently produced by harmful, non-renewable resources. More locally there is a large issue in regards to salinity affecting soils across the wheatbelt of Western Australia and therefore the production performance of farms in this region.
A species of plant that has been identified to help manage salinity issues in soils and that is native to the Western Australian wheatbelt is the Mallee Eucalyptus. Across the various subspecies it is able to grow across all of the Western Australian wheatbelt and grows well in lower rainfall areas of 350 to 600mm per year where other tree species struggle to grow. It is possible to grow Mallee Eucalypts in a belt configuration around existing crops or in a block configuration taking up a whole field themselves. There have been some efforts to increase the amount of Mallee Eucalypts included in agricultural projects since the mid 1990’s. It is estimated that about 14000 hectares have been planted so far and Mallee Eucalypts are not currently a common part of a farm planting mix.
There are many products able to be produced from Mallee Eucalyptus which can act as revenue streams for farmers however there is not the supply of biomass currently to support a Mallee Eucalyptus based industry nor the production capacity installed to make use of any supply created.
This research creates a model through gathering relevant values from academic papers and government based reports in order help farmers assess the financial viability of Mallee Eucalypts based on the specific conditions faced on their farm. The research found that there are currently products which are profitable such as woodchips and bioelectricity for most farm sizes above the very small. There are also products such as lignocellulosic ethanol and an Integrated Mallee Processing plant which are profitable given a sufficient amount of Mallee biomass produced. There are some products such as wood pellets, bio oil, eucalyptus oil and activated carbon which are currently not profitable due to similar production costs and selling prices. It was determined that an external catalyst, most likely from the government, is required to increase the utilisation of Mallee Eucalypts due to the large number of other possible sources to produce the same products. An increase in utilisation of Mallee Eucalypts should build the foundation of a Mallee based production industry and then through increased investment in the respective technologies lead to more products becoming profitable.
20
Kitchen, Julie Louise. « Nutrition and nutrional value of wheat grown in organic and conventional farming systems in South Australia ». Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phk618.pdf.
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Njaimwe, Arnold Ngare. « Tillage and crop rotation impacts on soil, quality parameters and maize yield in Zanyokwe Irrigation Scheme, South Africa ». Thesis, University of Fort Hare, 2010. http://hdl.handle.net/10353/460.
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Intensive tillage and monoculture cropping practices reduce soil C accumulation hence increasing soil vulnerability to chemical, physical and biological degradation. This study focussed on enhancing biomass production of wheat and oat winter cover crops as a means of increasing C sequestration in the low organic C soils of the central part of Eastern Cape Province. The specific objectives were (i) to evaluate the short-term effects of no till and cereal-fallow based crop rotations on; soil organic matter related parameters, pH and electrical conductivity, (ii) soil bulk density, water retention and aggregate stability, (iii) soil microbial biomass C and N, mineralizable N, soil respiration, and dehydrogenase enzyme activity, (iv) grain yield, soil nutrient concentration (N, P and K) and their uptake by maize, and (v) to identify soil parameters with high sensitivity to tillage under maize-fallow-maize, maize-wheat-maize and maize-oat-maize rotational cover cropping practices. The experiment was laid out as a split-plot arrangement in a randomized complete block design with 4 replicates. Tillage treatments (CT and NT) were applied on the main plots which measured 8 × 18 m while crop rotation treatments were applied in the subplots which measured 8 × 6 m. The rotation treatments were maize-fallow-maize (MFM), maize-wheat-maize (MWM) and maize-oat-maize (MOM). Weed control in NT plots involved preplant application of glyphosate to control mainly the grass weeds while post emergence weed management was done using Atrazine (485 atrazine and 15 g l-1 triazines). Initial weed control in CT plots was achieved through ploughing to a depth of 20 cm followed by disking while post emergence weed iii management was done by hand hoeing. Soil parameters measured were; (i) particulate organic matter (POM), soil organic carbon (SOC), total nitrogen (TN), pH and electrical conductivity (EC), (ii) soil bulk density (b), moisture at field capacity (FC), aggregate mean weight diameter (MWD) determined by fast wetting (FW), slow wetting (SW), mechanical breakdown by shaking (MB) and the stability index (SI), (iii) soil microbial biomass C (MBC) and N (MBN), mineralizable N (MN), soil respiration (SR), and dehydrogenase enzyme activity (DHEA). No-till increased POM and TN compared to CT in Lenye and Burnshill, respectively. The MWM and the MOM rotations increased TN relative to the MFM rotation in Lenye. The MWM and MOM rotations enhanced SOC relative to MFM in all sampled soil depths at Burnshill and similar observations were made under MOM rotation in the 5-20 cm depth in Lenye. The MWM and MOM rotations tended to depress soil pH relative to the MFM rotation in both sampled soil depths in Lenye while NT reduced soil pH relative to CT on the surface soil layer in Burnshill. Soil EC and pH varied with depth across tillage practices but both parameters remained within the ideal range for successful crop production over the study period. Soil stability index (SI) and aggregate MWD determined by FW, SW and MB were higher in Lenye compared to Burnshill. The MOM rotation enhanced the SI relative to MFM and MWM rotations at both sites. Scanning electron microscope (SEM) showed that more organic C was incorporated into the soil under NT and MOM rotation compared to CT and MFM rotation which had few organic coatings on the soil particles. Microbial properties varied with plant biomass input as influenced by tillage and type of rotational cover crop at both sites. Like in other past studies, NT showed higher levels of MBC, MBN, NM and SR at the soil surface layer compared to CT in Burnshill. No till increased MN iv relative to CT in both sampled soil depths in Lenye and resulted in higher DHEA compared to CT in Burnshill. The MOM rotation increased MBC, MBN, MN relative to MFM rotation especially within surface soil layer. Similar observations were made with respect to MN and SR in both sampled soil layers at Lenye. By contrast, the DHEA was higher under the MFM relative to the MWM and MOM rotations in Lenye but similar under the MFM and MOM rotations in Burnshill. Maize grain yield was not affected by both tillage and crop rotations but varied with cropping season. Comparable grain yields observed under the two tillage practices with similar fertilizer application rates indicated the advantage of NT over CT in saving on labour costs in maize production without compromising yields. High plant biomass retention under NT relative to CT contributed to high soil N and P levels under the former compared to the latter tillage practice especially on soil surface layer at both study sites. Principal component analysis (PCA) revealed that soil chemical and biological parameters closely linked to organic matter, namely SOC, MN, MBC and MBN showed the highest sensitivity to tillage and crop rotation treatments. Soil aggregate MWD determined by SW and b were the physical parameters which were highly altered by agronomic management practice. The MWM and MOM rotations were clustered together and clearly separated from the MFM rotation and this observed trend only applied to the 0-5 and 5-20 cm depths in Lenye site only. No till, MWM and MOM rotations enhanced POM, SOC and TN relative to CT and MFM rotation suggesting these practices have greater potential to improve soil chemical properties compared to intensive tillage and maize monoculture based production practices. Reduced soil b under MOM rotation and improved SI under NT compared to MFM and CT, respectively v indicate that these practices have the potential to improve degraded soils. Although not significantly different, NT values for MBC, MBN, MN, SR and DHEA were higher compared to CT indicating the potential of the practice to improve soil biotic activity relative to conventional tillage practices. No till enhanced surface soil nitrate N and extractable P compared to CT at both sites revealing the long-term potential of NT in improving the supply of these essential plant nutrients compared to CT. Principal component analysis showed that SOC, MN, K, P, MBC, MBN, soil aggregate MWD determined by SW and b were the most sensitive parameters to tillage and crop rotations. Therefore, these parameters could constitute the minimum data set for assessments of the impact of selected CA practices on soil quality attributes.
22
Weggler-Beaton, Karin M. « The beneficial and detrimental effects of sewage sludge applications in South Australia ». Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phw4113.pdf.
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Crawford, Michael Cameron. « Quantification of the belowground inputs of organic carbon by the annual pasture legume barrel medic (Medicago truncatula Gaertn.) ». Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phc8988.pdf.
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Bibliography: leaves 164-193. This study aims to quantify the belowground input of organic carbon by barrel medic using techniques that account for root death and decomposition as well as root secretion and exudation. It also investigates the effect of defoliation on carbon allocation within the plant so as to determine the potential for optimising carbon input to the soil through grazing management.
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Mupambwa, Hupenyu Allan. « Winter rotational cover crops effects on soil strength, aggregate stability and water conservation of a hardsetting cambisol in Eastern Cape Province, South Africa ». Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/453.
Texte intégralRésumé :
Winter rotational cover crops (WRCC) are often used to boost soil fertility and plant nutrition. However, selection and use of WRCC for soil physical improvement is usually overlooked. The objective of this study was to determine the effects of WRCC on soil strength, aggregate stability and water conservation of a hardsetting soil. The soil physical properties were determined after four rotations of growing monocultures of vetch (Vicia dasycarpa cv. Max), lupin (Lupinus angustifolius cv. Tanjil) and oats (Avena sativa cv. Sederberg) and after two rotations of growing bicultures of oats (Avena sativa cv. Pallinup) and vetch (Vicia dasycarpa cv. Max) across two soil layers, 0 to 15 cm and 15 to 30 cm. The individual WRCC and a weedy fallow constituted the treatments in the monoculture study whilst in the biculture study the various combinations of WRCC namely; 90% oat plus 10% vetch (O90V10); 70% oat plus 30% vetch (O70V30) and 50% oat plus 50% vetch (O50V50) and a weedy fallow constituted the treatments. After four rotations with cover crop monocultures, oats significantly (P ≤ 0.05) reduced penetration resistance (PR) whilst vetch increased PR in both soil layers compared to the weedy fallow control. The effect of the biculture treatments was only experienced within the 15 to 30 cm depth. The treatments O50V50 and O70V30 increased the PR compared to the control. The WRCC in monoculture significantly increased the soil aggregate stability relative to the control in both soil layers. Vetch, lupin and oats resulted in a 41.7%; 20.4% and 15.7% increase in MWD in the 0 to 15 cm soil layer and 47.2%; 44.2% and 39.7% in the 15 to 30 cm depth, respectively. An increase in aggregate stability was associated with increased macro-aggregation. Under the biculture, WRCC slightly increased, non- significantly, the aggregate stability. Both hot water and dilute acid extractable polysaccharides showed no significant correlation with aggregate stability in the two studies. Oats monoculture resulted in a significant difference (P ≤ 0.05) on cumulative infiltration compared to the control. However, after 2 h vetch and lupin showed no significant difference from the control on cumulative infiltration. Oats resulted in a 7.8% increase in final infiltration rate (FIR) whilst vetch and lupin reduced FIR by 9% and 16.7% respectively, compared to the control. Bicultures of oats and vetch significantly (P ≤ 0.05) increased cumulative infiltration compared to the weedy fallow control. A similar significant increase in FIR was also observed under bicultures. The treatments O50V50; O90V10 and O70V30 resulted in a 163.3%; 113.3% and 105.4% increase in FIR respectively, compared to the control. Cover crop monocultures significantly (P ≤ 0.05) increased plant available water (PAW) compared to the weedy fallow, with vetch, oats and lupin resulting in a 28.3%; 22% and 23.9% increase respectively, in PAW. However, no significant differences were observed on PAW after two rotations with bicultures. Compared with winter weedy fallow, WRCC improved most of the soil physical properties under study, with the most suitable results expected under bicultures compared to monocultures. Under CA, selection of WRCC like oats, vetch and lupin, one should therefore take into consideration their effects on soil physical properties as a selection criterion and not biomass and fertility alone.
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Swarts, Derek Juan. « Soil community structure and litter decomposition under irrigated Eucalyptus Globulus in South Western Australia ». Connect to thesis, 2006. http://portal.ecu.edu.au/adt-public/adt-ECU2006.0051.html.
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Venter, Annari. « Comparing plant yield and composition with soil properties using classical and geostatistical techniques ». Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/23916.
Texte intégralRésumé :
Plant nutrient management plays a vital role in the success or failure of modern Lucerne production. In South Africa, Lucerne is produced under a wide range of climatic conditions, under dryland and irrigation and in some areas throughout the year. This means that there is a continuous demand for nutrients under a wide range of environmental conditions. The most important factors affecting the nutrient requirement of Lucerne is yield, the cutting schedule, climate and management practices. To enable site-specific crop requirements, the spatial variation of soil and plant properties within a field can be managed with the use of geostatistical techniques. Some work has also been done to evaluate the use of geostatistics in the design of agricultural field experiments to provide better field characterization and improve plot layout. The aim of this study was to compare plant yield and composition with soil properties using both classical and geostatistical techniques. The study was conducted from June 2001 to February 2002 on an 18ha Lucerne stand in the Brits district in the North West Province. A rectangular area of 160m X140m was demarcated as the study area and comprised of two soil units (Hutton and Shortlands forms). Seventy-two sampling points (nodes) were laid out on a 20m square grid, with an additional 90 sampling points laid out on a 2.5m square grid at six randomly selected node points. Soil (0-300 mm) and plant samples were taken within a 0.6m square at each of the sampling points for chemical analysis. Starting in June 2001, yield sampling was done on six occasions, at approximate intervals of 5 weeks. A randomized complete block design trail layout was superimposed on the geostatistical grid design and consisted of seven pseudo treatments, replicated four times. Basic statistical analysis were performed and spatial presentations of the variation of the plant and soil properties and Lucerne yield were made using geostatistical analyses. Analyses of variance were used to test for differences between pseudo treatments for all plant and soil properties. The two soils on the stud site, exhibited differences in certain properties, which caused a bi-modal population in the data. Poor correlations were found between plant nutrient uptake and soil properties as well as yield, with little or no resemblance when comparing their spatial distribution. This emphasizes the fact that the uptake of elements is not solely dependant on the concentrations thereof in the soil solution, but on other factors. Temporal variations in Lucerne yield were also observed. Although there were large differences in spatial variation of Lucerne yields across harvesting events, similar spatial patterns were evident. From an analysis of variance of the RCB design it was concluded that the experimental field was homogeneous enough to lay out a standard block design experiment. However, scrutiny of the structure of spatial variability of pH(H2O) revealed that the standard RCB designs did not provide homogeneous blocks with respect to soil variability. The consequent redesign of the experiment whereby all plots were randomly allocated to treatments and replications, led to dramatically different results: significant differences were obtained for plant and soil properties as a function of the pseudo treatments. From this study it is clear that spatial variability of soil and plant properties can jeopardize the results of a standard block design field experiment and it is therefore recommended that the layout of field experiments should be designed to the cognizance of the spatial variation of a soil property that correlated highly with a chosen response variate.Dissertation (MSc (Soil Science))--University of Pretoria, 2007.
Plant Production and Soil Science
unrestricted
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Marsudi, Nada D. S. « Identification and characterization of root nodule bacteria from South-Western Australia soils able to nodulate Acacia saligna ». Thesis, Marsudi, Nada D.S. (1997) Identification and characterization of root nodule bacteria from South-Western Australia soils able to nodulate Acacia saligna. Masters by Research thesis, Murdoch University, 1997. https://researchrepository.murdoch.edu.au/id/eprint/51836/.
Texte intégralRésumé :
One hundred and thirty root nodule bacterial strains were isolated from nodules of Acacia saligna grown in ten different soils from nine locations in South- Western Australia. These isolates were confirmed as root nodule bacteria by reinoculation onto their host plant (A. saligna). Based on their morphological characteristics and growth rates on yeast mannitol agar (YMA), thirty nine strains were classified as fast-growing rhizobia and ninety four as slow-growing bradyrhizobia. The fast-growing strains were found in all soils except one from Narrikup which had the lowest pH (4.62).
Selected strains (20 fast-growing and 20 slow-growing) were characterized for their ability to grow:
•at acid pH (5 ± 0.2), or at alkaline pH (8.8 ±0.1)
•at 37°C
•on mannitol, fructose, arabinose, lactose or sucrose as sole carbon sources
•in the presence of 1 -3% (w/v) NaCl
The slow-growing bradyrhizobia were more acid-tolerant than the fastgrowing rhizobia, while the fast-growing rhizobia were more alkali tolerant than the slow-growing bradyrhizobia. Most fast-growing rhizobia grew at 37°C, whereas only two slow-growing bradyrhizobia could grow at this temperature. Both fast- and slowgrowing root nodule bacteria grew on mannitol, fructose and arabinose as a sole carbon source. All of the fast-growing rhizobia utilized the disaccharides (lactose and sucrose), whereas the slow-growing bradyrhizobia did not. All the slow-growing bradyrhizobia were sensitive to salt and did not grew even at 1% (w/v) NaCl. All of the fast-growing rhizobia grew at 1% NaCl and some at 3% NaCl.
In order to investigate the diversity within a segment of the 16S rRNA genes of these root nodule bacterial strains, 10 fast-growing rhizobial strains and 10 slowgrowing bradyrhizobia were selected, with Sinorhizobium meliloti WSM 419 as a control strain. A 260-264 bp segment of DNA from each strain (corresponding to positions 44 to 337 in the Escherichia coli 16 S rRNA gene) was amplified using the polymerase chain reaction (PCR) method and the amplified DNA sequenced. The 16S rRNA (DNA) sequences were then compared and aligned to those known for reference root nodule bacterial strains from the GenBank Data Library leading to a phylogenetic unrooted tree for the strains from A. saligna.
Analysis of the 16S rRNA gene sequences confirmed that the root nodule bacterial strains able to nodulate A. saligna can be separated into fast- and slow-growing strains.
The fast-growing rhizobia can be divided into two groups. The first group consists of six strains which showed 96.5-100% similarity over 260 bp to Rhizobium leguminosarum biovar phaseoli U29388. The second group consists of four strains which showed 97.7-100% similarity over 260 bp to Rhizobium tropici U38469. The slow-growing bradyrhizobia could also be grouped together. Six strains showed 97.3- 99.2% similarity over 264 bp to Bradyrhizobium japonicum Z35330. Three strains showed 99.2-100% similarity over 264 bp to Bradyrhizobium sp. (Lupinus) X87273 and strain YL68 showed 100% similarity over 262 bp to Bradyrhizobium sp. (Lupinus) U69636. S. meliloti WSM419 showed 100% similarity over 260 bp to Sinorhizobium sp. Z78204.
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Nathan, Muhammad. « Clay movement in a saline-sodic soil toposequence ». Title page, contents and summary only, 2001. http://web4.library.adelaide.edu.au/theses/09A/09an274.pdf.
Texte intégralRésumé :
Includes bibliographical references (leaves 78-86) In the Herrmanns sub-catchment in the Mt. Lofty Ranges (near Mt. Torrens) soil sodicity was the dominant factor in causing clay to disperse in the eroded area along the foot slopes, wheras in non-eroded areas of the mid-slopes and on the stream banks, the dispersive power of sodicity was attenuated by the flocculative power of other soil properties.
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Huang, Chunyuan. « Mechanisms of Mn efficiency in barley ». 1996, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phh8739.pdf.
Texte intégralRésumé :
Bibliography: leaves 131-153. This thesis investigates the mechanisms of manganese (Mn) efficiency (genetic tolerance to Mn-deficient soils) in barley (Hordeum vulgare L.) at both physiological and molecular levels.
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Collins, Shane. « Residue composition influences nutrient release from crop residues ». University of Western Australia. School of Earth and Geographical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0171.
Texte intégralRésumé :
[Truncated abstract] A greater adoption of stubble retention, minimum-till and no-till farming practices for the purposes of conserving soil, water and fertility requires a greater understanding of the complexity of physical and chemical interactions between the soil and crop residues. There is currently insufficient knowledge to allow reliable predictions of the effects of different residue types in different environments on soil fertility and crop growth, owing to the many residue characteristics and environmental interactions that have been shown to affect decomposition or nutrient release. The role of fibre and nutrient composition in nutrient release from crop residues, and implications for residue management techniques, were studied. Canola, lupin and field pea residues, obtained from farmland in Meckering and Northam, Western Australia, were separated into upper and basal stems, leaves, and siliques or pods. This was done to provide materials with a wide range of chemical and physical characteristics, and also allowed consideration of differential residue management of plant organs, such as comparing harvested canola siliques and retained canola stubble. Pre-treatment by chopping and/or humidification was applied to residues to provide some information about the processes of nutrient release. Residues were subjected to simulated rainfall to assess nutrient leaching from plant material, and placed on soil in pots in constant-temperature glasshouse conditions to assess decomposition. Amounts and rates of change of residue fibre and nutrients were determined throughout leaching and decomposition. Energy Dispersive X-ray (EDX) microanalysis was used to assess the location of diffusible ions in air-dried residues and the effects of humidification on nutrient positioning and release. ... However, the release of calcium and magnesium depended on the decomposition of the more recalcitrant components such as cellulose and lignin, as supported by microscopy results showing changes in nutrient distribution following humidification. The proportionality of amounts of calcium and magnesium leached and released during decomposition is likely to suggest a similarity of chemical form more than similarity of function or position of the two elements. Management of crop residues for maximising and optimising the timing of release of different nutrients will need to take into account the placement of different plant types and parts, particle sizes distribution and pre-treatment of material to efficiently manage short- and long-term soil fertility to sustain crops, particularly on degraded soils. Significant nutrient release of potassium, sulphur and magnesium from crop residues can be achieved from surface placement, with the release of potassium and sulphur managed by modifying residue particle size through appropriate harvesting, ploughing or sowing implement selection. High nutrient uptake crops and plant parts where they can be economically viable to grow or separated by the harvesting technique are particularly valuable as sources of nutrients and soil organic matter.
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Puta, Usanda. « Effects of genetically modified maize (MON810) and its residues on the functional diversity of microorganisms in two South African soils ». Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/419.
Texte intégralRésumé :
Genetically modified (GM) crops are commercially cultivated worldwide but there are concerns on their possible negative impacts on soil biodiversity. A glasshouse study was conducted to determine effects of Bt maize residues on soil microbial diversity. Residues of Bt maize (PAN 6Q-308B) and non-Bt maize (PAN 6Q-121) were incorporated into the soil and corresponding maize seeds planted. The treatments were replicated three times. Fertilizer and water application were similar for both treatments. Rhizosphere and bulk soil was destructively sampled from each treatment and analyzed for microbial community level physiological profiles using Biolog plates with 31 different carbon substrates. Absorbance in the Biolog plates was recorded after 72 h of incubation at 20oC. Arbuscular mycorrhizal fungi spore counts were also determined. Field studies were conducted at the University of Free State and University of Fort Hare Research Farms to determine the effects of growing Bt maize on soil microbial diversity. One Bt maize cultivar (PAN6Q-308B) and non-Bt maize (PAN6Q-121) were grown in a paired experiment at University of Free State farm, while two Bt maize (DKC61-25B and PAN6Q-321B) and their near-isogenic non-Bt maize lines (DKC61-24 and PAN6777) were grown in a randomized complete block design with three replicates. Fertilization, weed control and water application, were similar for both Bt maize cultivars and their non-Bt maize counterparts. Rhizosphere soil samples were collected by uprooting whole plants and collecting the soil attached to the roots. The samples were analysed for microbial diversity and for arbuscular mycorrhizae fungal spore counts. Principal component analysis showed that soil microbial diversity was affected more by sampling time whereas genetic modification had minimal effects. Presence of residues also increased the diversity of microorganisms. Mycorrhizal fungal spores were not affected by the presence of Bt maize residues. Growing Bt maize had no effect on the soil microbial diversity in the rhizosphere.
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Harris, Mark Anglin. « Some organic amendments for heavy metal toxicity, acidity and soil structure in acid-sulphate mine tailings / ». Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phh3148.pdf.
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Horsnell, Tara Kathleen. « Quantifying thresholds for native vegetation to salinity and waterlogging for the design of direct conservation approaches ». University of Western Australia. School of Environmental Systems Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0082.
Texte intégralRésumé :
A field-based project was undertaken to develop and test a mechanism which would allow for the correlation of the health of vegetation surrounding playa lakes in south-west Australia with the natural variation in salinity and waterlogging that occurs spatially and temporally in natural systems. The study was designed to determine threshold ranges of vegetation communities using moderately extensive data over short temporal periods which will guide the design of potential engineering solutions that manipulate hydrological regimes to ultimately conserve and protect native vegetation. A pair of playa lake ecosystems, surrounded by primary production land, was modelled with hydro-geological data collected from March 2006 to March 2007. The data was used to determine the hydroperiods of vegetation communities fringing playa lakes and provide insight into the areas and species that are most affected by extreme rainfall events which are hypothesised to have a significant, rapid deleterious effect on the ecosystems. The methodology was multi-faceted and included; a detailed topographical survey; vegetation surveys; hydrological and hydro-geological monitoring over a 12 month period. 4 The hydro-geological data and vegetation data was linked with the topographical survey at a high resolution for spatial analysis in a Geographic Information System (GIS) to determine the degree of waterlogging experienced by vegetation communities over the monitoring period. The study has found that the spatial and temporal variability of hydroperiods has been reduced by rising groundwater levels, a result of extensive clearing of native vegetation. Consequently populations are becoming extinct locally resulting in a shift in community composition. Extreme summer rainfall events also have a significant impact on the health of vegetation communities by increasing the duration of waterlogging over an annual cycle and in some areas expanding the littoral zone. Vegetation is most degraded at lower positions in the landscape where communities are becoming less diverse and dominated by salt tolerant halophytic species as a result of altered hydrological regimes. Some species appear to be able to tolerate groundwater depths of less than 2.0 m from the surface, however there are thresholds related to the duration at which groundwater is maintained at this depth. Potential engineering solutions include groundwater pumping and diverting water through drains to maintain sustainable hydroperiods for vegetation in areas with conservation value. The effectiveness and efficiency of the engineering solutions can be maximised by quantifying thresholds for vegetation that include sustainable durations of waterlogging. The study has quantified tolerance ranges to salinity and waterlogging with data collected over 12 months but species may be experiencing a transition period where they have 5 sustained irreversible damage that will result in their eventual mortality. With long-term monitoring, the methodology developed and tested in the study can be used to quantify the long-term tolerance ranges that are important for the application of conservation approaches that include engineering solutions.
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Adolphson, Honi M. « Acari (Mite) Abundance And Diversity In Soil And Litter Layers Of Eucalyptus Globulus Labill (Tasmanian bluegum) Plantations In Southwest Western Australia ». Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2000. https://ro.ecu.edu.au/theses/1542.
Texte intégralRésumé :
With the increased planting of E. globulus monoculture plantations, concerns surround the impact these mass plantings will have on the soil environment and wider ecosystem. Soil and litter mites are the dominant saprophages of terrestrial ecosystems, contributing to decomposition processes through their comminution and grazing activities. Despite the importance of mites to decomposition processes, there have been no investigations to date of the litter and soil communities under these plantations within Australia. This study investigated the impact of Eucalyptus globulus subsp. globulus (Tasmanian bluegum) monoculture plantations on the diversity and abundance of the soil and litter acarine (mite) fauna. Mite communities under three 8 year-old E. globulus plantations sited on reclaimed pastureland were compared with an adjacent native E. marginata (jarrah) forest and a grazed pasture in the mediterranean-type region of southwest Western Australia. Sites were sampled in spring 1997 and new sites randomly selected in autumn 1998. Large seasona1 variations in abundance and diversity were found between the sampling periods of spring 1997 and autumn 1998, influenced considerably by soil moisture. Species richness was consistently higher in both the soil and litter layers under native jarrah forest, with the E. globulus plantations intermediate in species richness between the native forest and grazed pasture. A total of 114 mite species/morphospecies was recognized; 16 Mesostigmata, 52 Prostigmata, 45 Oribatida (Cryptostigmata) and 1Astigmata. Species diversity in the surface litter was higher under the native forest, reflecting the greater heterogeneity of the litter. Diversity in the underlying soil was similar for the native forest and E. globulus plantation, although there were considerable differences in species richness. Soil diversity in the pasture was very poor in comparison to the two forest systems, reflecting the absence of a litter layer and reduced niche dimensions. The monospecific E. globulus litter possibly reduced niche variety by simplifying the physical habitat and reducing the variety of resources available for the saprophagous fauna, of which the oribatid mites are a major component. Consequently, the number of families represented in the microphytophagous, phytophagous and predator functional groups under the E. globulus plantation may have been reduced. The most common oribatid families under the plantation were those often reported from disturbed habitats, Oppiidae and Tectocepheidae, and those common in many habitats, Oppiinae and Oppiellinae. An important management implication arising from this study is that these plantations would harbour a more diverse mite fauna if planted as a mixed tree stratum.
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Pearse, Stuart James. « Carboxylates in the rhizosphere of canola, wheat, lupins and pulses : their role in P acquisition from sparingly soluble forms ». University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0069.
Texte intégralRésumé :
[Truncated abstract] Native Australian soils contain very low amounts of phosphorus. The soils of southwestern Australia are ancient and highly weathered. Consequently, the availability of phosphorus in these soils is too low for cropping purposes, so the application of P is necessary to maintain productivity. When P is applied to soil, typically as soluble superphosphate, it tends to be transformed to increasingly less soluble forms over time. Sparingly soluble forms of soil P are relatively inaccessible to Triticum aestivum; however, many grain legumes have a higher P-acquisition efficiency, allowing them to access pools of soil P that T. aestivum cannot. The P-acquisition efficiency of some grain legumes has been attributed in part to their ability to release large quantities of carboxylates, coupled with the development of cluster roots for species such as Lupinus albus. There are a number of unexplained observations in terms of the P-acquisition efficiency of grain legume species and the way that those species respond to P fertilisation. This PhD project aimed to study carboxylate release from a range of crop species, and investigate its role in variation among species for acquisition of phosphorus from sparingly soluble forms (chapter 1). ... L. albus (chapter 5). There was considerable variation in P acquisition among accessions. The variation cannot be attributed to differences in carboxylate release, cluster-root development or whole root system rhizosphere extract pH as measured in this study. We hypothesise that the variation might be attributed to differences in the ratio of release of protons and other cations localised around cluster roots. In conclusion studies of carboxylate exudation and sparingly soluble forms should use more than a single form if the aim is to draw generalised conclusions on P-uptake efficiency from sparingly soluble forms. Comparative studies of a range of species are a useful tool for enhancing our understanding of root physiology. While the benefit of carboxylates for providing access to poorly soluble P has been demonstrated, questions remain as to potential other roles for carboxylates, particularly in species that do not form cluster roots. Variation in P uptake among accessions of L. albus is present, and more work on proton release and ion balance of root clusters is necessary to understand intraspecific variation.
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Roux, F. A. « Die invloed van spesifieke grond en klimaats parameters op wingerdprestasie, wynkwaliteit en -karakter ». Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1343.
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McDonald, Kathi. « Variation in morphology, salinity and waterlogging tolerance and resource allocation in strawberry clover (Trifolium fragiferum L.) : implications for its use in mildly saline soils in southern Australian farming systems ». University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0105.
Texte intégralRésumé :
[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater
38
Vagh, Yunous. « Mining climate data for shire level wheat yield predictions in Western Australia ». Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/695.
Texte intégralRésumé :
Climate change and the reduction of available agricultural land are two of the most important factors that affect global food production especially in terms of wheat stores. An ever increasing world population places a huge demand on these resources. Consequently, there is a dire need to optimise food production.
Estimations of crop yield for the South West agricultural region of Western Australia have usually been based on statistical analyses by the Department of Agriculture and Food in Western Australia. Their estimations involve a system of crop planting recommendations and yield prediction tools based on crop variety trials. However, many crop failures arise from adherence to these crop recommendations by farmers that were contrary to the reported estimations. Consequently, the Department has sought to investigate new avenues for analyses that improve their estimations and recommendations.
This thesis explores a new approach in the way analyses are carried out. This is done through the introduction of new methods of analyses such as data mining and online analytical processing in the strategy. Additionally, this research attempts to provide a better understanding of the effects of both gradual variation parameters such as soil type, and continuous variation parameters such as rainfall and temperature, on the wheat yields.
The ultimate aim of the research is to enhance the prediction efficiency of wheat yields. The task was formidable due to the complex and dichotomous mixture of gradual and continuous variability data that required successive information transformations. It necessitated the progressive moulding of the data into useful information, practical knowledge and effective industry practices. Ultimately, this new direction is to improve the crop predictions and to thereby reduce crop failures.
The research journey involved data exploration, grappling with the complexity of Geographic Information System (GIS), discovering and learning data compatible software tools, and forging an effective processing method through an iterative cycle of action research experimentation. A series of trials was conducted to determine the combined effects of rainfall and temperature variations on wheat crop yields. These experiments specifically related to the South Western Agricultural region of Western Australia. The study focused on wheat producing shires within the study area. The investigations involved a combination of macro and micro analyses techniques for visual data mining and data mining classification techniques, respectively.
The research activities revealed that wheat yield was most dependent upon rainfall and temperature. In addition, it showed that rainfall cyclically affected the temperature and soil type due to the moisture retention of crop growing locations. Results from the regression analyses, showed that the statistical prediction of wheat yields from historical data, may be enhanced by data mining techniques including classification.
The main contribution to knowledge as a consequence of this research was the provision of an alternate and supplementary method of wheat crop prediction within the study area. Another contribution was the division of the study area into a GIS surface grid of 100 hectare cells upon which the interpolated data was projected. Furthermore, the proposed framework within this thesis offers other researchers, with similarly structured complex data, the benefits of a general processing pathway to enable them to navigate their own investigations through variegated analytical exploration spaces. In addition, it offers insights and suggestions for future directions in other contextual research explorations.
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Schreuder, F. A. « An investigation into global distribution systems in the crop protection industry and the development of distribution system managment model for particular application in South Africa and Australia ». Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/21185.
Texte intégralRésumé :
Thesis (PhD)--Stellenbosch University, 2002.ENGLISH ABSTRACT: The traditional ways in which manufacturers of crop protection products exercised control over distribution systems have diminished in their impact. Control was based on quality products, the power of the brand, an installed customer base and a broad portfolio of mostly patented products. Manufacturers of crop protection products need to review the manner in which these products are marketed, which distribution system management models are to be used, and the importance that is placed on distribution system management in the marketing mix. The primary aim of this study was defined as: "The development of appropriate distribution system management models for application in South Africa and Australia~. The secondary aim was defined as: "Establishing the key factors which determine the relationship between manufacturers and distributorsn . The dominant economic characteristics of the global crop protection industry are deemed to consist of a global market valued at US $28,090 mio, a mature market in a decline phase, the rapid consolidation of industry players, increased generic product manufacturer activity and an overall decline in manufacturer profitability. In South Africa crop protection product manufacturers use approximately 46 independent distributors to market products on farms through 600 affiliated commissioned sales agents. In Australia the distribution of crop protection products is much more concentrated. Distribution is essentially controlled by five national distributors and their coupled salaried representatives. Manufacturers therefore rely on third parties for the marketing of their products to farmers in both countries. The applicable problem statement has been formulated to select a distribution system management model that will: (i) optimally balance direct distribution related cost and subsequent levels of control over distributors; (ii) maximise the probability that a distributor will buy and actively promote the complete product portfolio of a for high levels of interpersonal relationship maintenance; and (vi) manufacturers have to instill the philosophy that distribution system management is part of a manufacturer's strategic business and marketing focus and not simply a task to be performed by a third party.
AFRIKAANSE OPSOMMING: Die tradisionele maniare waarop die vervaardigers van oesbeskermingsprodukte beheer kan uitoefen oor verspreidingsisteme is nie meer so suksesvol nie. Beheer was gebaseer op kwaliteil produkte, die mag van die handelsmerk:n gevestigde klientebasis en 'n wye produktereeks,bestaande uit gepatenteerde produkte, Vervaardigers van oesbeskermingsprodulcte moet die wyse waarop hierdie produkte bemark word, watter verspreidingsisteem bestuursmodelle gebruik word en die belangrikheid wat geplaas word op die bestuur van die verspreidingsisteme in die totala bemarkingspoging in heroorweging neern. Die primere doelstelling van hierdie studie is: "Die ontwikkeling van toepaslike verspreidingsisteem bestuursmodelle vir toe passing in Suid-Afrika en Australia. "Die sekondere doelstelling is: "Die vas stelling van die sleutelfaktore wat die verhouding tussen velVaardigers (verskaffers) en verspreiders bepaar. Die dominante ekonomiese kenmerke van die globale oesbeskermingsindustrie is 'n markwaarde in VSA $ 28,090 miljoen, 'n stagnante mark in 'n agteruitgang lase, die drastiese konsolidasie van die industrie spelers, 'n toename in die aktiwiteite van die generiese produkvervaardigers en 'n algemene daling in die winsgewindheid van die vervaardigers. In Suid-Afrika gebruik die vervaardigers van die oesbeskermingsprodukte ongeveer 46 onafhanklike verspreiders om die produkte op plaasvlak te bemark met behulp van 600 geaffilieerde kommissie agente. Die verspreiding van oesbeskermingsprodukte is baie meer gekonsentreerd in Australie. Verspreiding word in wese beheer deur vyf nasionale verspreiders en hulle spanne van verkoopsteenwoordigers wat 'n salaris verdien. In beide lande moet velVaardigers van oesbeskermingsprodukte staatmaak op onafhanklike instansies vir die bemarking van hul produkte op plaasvlak. Die probleemsteiling is dus die uitdaging om 'n verspreidingsisteem bestuursmodel t9 ontwikkel wat: (i) . n optima Ie balans sal gee tussen direkte verspreidingskoste en gekoppelde vlakke van beheer oor verspreiders; (ii) die waarskynlikheid dat . n verspreider die betrokke produkreeks van die vervaardiger sal aankoop en aktief sal promoveer; (iii) dit kan bereik in . n mark waar verspreiders talle bronne het van soortgelyke produkte teen kompeterende pryse. Gebaseer op die sekondere navorsing wat gedoen is wit dit blyk dat daar 'n algemene konsensus is dat daar n nei9in9 weg is van transaksie spesifieke besigheidsverhoudings na besigheidsverhoudings gebaseer op vennootskap gebaseerde benaderings in die interaksie tussen vervaardigers (verskaffers) en verspreiders. Hierdie tipe besigheidsverhouding word gekenmerk deur hoe vlakke van onderlinge vertroue, wedersydse verbintenis, konflik hanteringsmeganismes en goeie wedersydse kommunikasie. Primere navorsing is in Suid-Afrika (253 respondente) en Australia (180 respondente) gedoen. Implikasies vir die konstruksie van verspreidingsisteem bestuursmodelle wat voortvloei uit hierdie navorsing sluit in die belangrikheid dat on vervaardiger on wye en gesogte produkreeks het, die vereiste dat produkte beproefde effektiwiteit het, produkte kompeterend geprys is, die vereiste vir hoe vlakke van verskaffer opvolgdiens en die vereiste vir goeie interpersoonlike verhouding tussen werknemers van beide die vervaardigers en die verspreiders. Hierdie elemente moet ondermeer gerugsteun word deur goeie kommunikasiesisteme. Die "idea Ie" verspreidingsisteem bestuursmodelle is vervolgens voorgestel vir beide Suid-Afrika en Australie, gebaseer op die bevindinge van ondermeer die sekondere- en primere navorsing. Hierdie mode lie het ten doel om toepaslike strukture en besigheidsbenaderings vir vervaardigers daar te stel om hulle behulpsaam te wees om die geidentifiseerde behoeftes van die verspreiders aan te spreek.
40
Jenkins, Sommer. « Ecophysiological principles governing the zonation of puccinellia (Puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) on saline waterlogged land in south-western Australia ». University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0133.
Texte intégralRésumé :
Puccinellia (puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) often show ecological zonation in saline landscapes, with puccinellia occurring in less elevated more saline/waterlogged locations, and tall wheatgrass occurring in more elevated less saline/waterlogged locations. The aims of this study were to: (a) characterize the observed ecological zonation at a field site, (b) quantify the effects of variables likely to explain growth differences of the two plants in glasshouse experiments, and (c) identify and compare anatomical and physiological mechanisms that explain these zonation patterns. At an experiment in the field near Kojonup (0522824E, 6244579N), puccinellia was found to colonise the lower more severely salinised and waterlogged zones of the landscape, with tall wheatgrass occupying the higher less affected zones. These differences in zonation were clearly associated with variance in soil salinity and water-table depth. Glasshouse experiments in soil revealed that low pH values, low calcium concentrations and variation in salinity alone did not explain the ecological zonation observed in the field. However, there was a substantial difference in the responses of the two plant species to waterlogging in combination with salinity. Puccinellia grew better under saline waterlogged conditions than tall wheatgrass, which was associated with better regulation of Na+ and K+ under saline/waterlogged conditions than in tall wheatgrass. Under non-saline conditions, waterlogging (hypoxia) decreased shoot weights in puccinellia by 15% and in tall wheatgrass by 20%. Similar growth results were obtained in nutrient solution culture, where waterlogging was simulated by lowering the oxygen in solutions through bubbling with N2 gas. Under saline hypoxic conditions, puccinellia, compared to tall wheatgrass, showed increased growth and maintenance of selectivity of K+ over Na+ across adventitious roots. Solution experiments revealed adaptive traits responsible for conveying better growth and ion maintenance present in puccinellia, but not tall wheatgrass, such as inducement of a barrier to radial oxygen loss in the basal regions of adventitious roots (not previously reported in the literature for puccinellia), formation of root aerenchyma and packing of cortical cells and suberin deposition in hypodermal and endodermal root cell layers. These results should assist in targeting pasture species, and predicting their growth response, in saline and waterlogged landscapes. Further work on examining the genetic material of puccinellia is warranted in order to identify genes that could be transferred into crop plants to convey salt and waterlogging tolerance.
41
Poulter, Rachel. « Investigating the role of soil constraints on the water balance of some annual and perennial systems in a Mediterranean environment ». University of Western Australia. Faculty of Agriculture, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0018.
Texte intégralRésumé :
This thesis compares the in situ water balance of common annual production systems (wheat, lupin, subclover and serradella) with a grazed perennial system (lucerne) at a site in the Avon Catchment, Western Australia. Using a physically-based water balance approach the value of a plant based solution in redressing the hydrological imbalance that has become a feature of much of the dryland agricultural region of Western Australia is investigated. The effectiveness of lucerne in providing greater available storage for buffering large rainfall events, as compared to the annual systems, is illustrated. Continued transpiration following out-of-season rainfall events maintains a larger available storage capacity. In contrast, the annual systems that are fallow over summer only withdrew a small fraction of water by soil evaporation between rainfall events. Under annual systems, the profile moisture store was sequentially increased to the extent that additional increments of rainfall could potentially contribute to deep drainage. A particular focus of this study has been to investigate the presence of soil constraints to root growth, and to assess how these constraints affect the water balance. A site survey indicated the soil penetration resistance was sufficient to impose a physical constraint to root growth. Published literature on the site shows soil acidity is also at a level imposing chemical constraints to root growth. A root growth model “Rootmodel”, for predicting root growth with and without soil constraints is examined in detail as a method for providing root growth parameters for inclusion into the numerical water balance model, SWIM based on Richard’s equation. Functions developed from “Rootmodel” adequately describe the effect of profile limitations to root growth, such as soil strength, moisture availability and temperature. Recommendations are made for inclusion of a growth suppressing function in “rootmodel” based on the chemical limitation of low pH. The effects of soil acidity on the root growth of several species is investigated experimentally and the resultant root data provided a reference point by which the simplified prediction of root growth built into SWIM could be adjusted using a linear reduction function. A similar linear reduction function is also employed to impose a physical constraint in the form of high penetration resistance.
42
Khetsha, Zenzile Peter. « The effect of potassium and water quality on the yield and oil quality of Rose Geranium (Pelargonium graveolens L.) ». Thesis, Bloemfontein : Central University of Technology, Free State, 2013. http://hdl.handle.net/11462/189.
Texte intégralRésumé :
Thesis (M. Tech. (Agriculture)) -- Central University of Technology, Free state, 2014The main objective of the study was to determine the effect of different potassium concentrations and water quality (salt) compared with the current scientifically accepted potassium threshold level and standardised water quality on the yield, oil composition and leaf morphology of rose geranium (Pelargonium graveolens L.) when grown in different potting-bag sizes and root media under temperature controlled condition. To achieve this objective, two trials were conducted. The first experiment evaluated potassium concentrations at 1.3, 3.3, 5.3 and 7.3 mmol L-1 and potting-bag size of 5 and 10 L. Treatments were arranged in a randomised complete block design assigned in a split plot layout. The main plots consisted of potassium concentration and the pottingbag sizes were allocated to sub-plots. Plant height, potassium content, linalool, geraniol, geranyl formate and the citronellol to geraniol ratio (C:G) were affected by potassium. Plant height, number of branches, the branch to height ratio (B:H), foliar fresh mass (FFM) and oil yield were significantly increased when 5 L potting bags were used. Plant foliar mass was significantly increased by the interaction between 5.3 mmol K L-1 and 5 L potting bags. In the second experiment salt levels applied at 1.6, 2.4, 3.2 and 4.0 mS cm-1 and root media (sand and sawdust) were evaluated. A split plot experimental layout was also used in this trial, with the salt levels allocated to the main plots. The sub-plots were allocated to the root medium. High salt level of 4.0 mS cm-1 reduced the number of leaves, plant height, number of branches, B:H ratio, leaf area, chlorophyll content and foliar fresh mass significantly. The number of leaves, leaf area and FFM were significantly increased where sawdust was used. Time of the day significantly affected stomatal conductance, and the opening of most stomata occurred at 10:00. Geranyl formate and the C:G ratio were significantly affected by salt at 4.0 mS cm-1. Salt induced the development of capitates trichomes. The abaxial leaf surface had a higher number of trichomes than the adaxial leaf surface. A strong polynomial (r2=0.97) relationship was found between capitates trichomes and salt levels. High densities of capitates trichomes were found at high salt level of 4.0 mS cm-1. Although the development of asciiform trichomes was induced, it was at an insignificant level. Trichome densities are therefore not affected by salt. It was therefore concluded that the application of 5.3 mmol K L-1 concentration and the use of 5 L potting bags improves the yield and oil quality of rose geranium. It was evident from this study that rose geranium might Salt induced have some degree of tolerance to salt. It was therefore concluded that rose geranium is a moderately salt-sensitive crop.
43
Farhoodi, Alireza. « Lime requirement in acidifying cropping soils in South Australia / by Alireza Farhoodi ». Thesis, 2002. http://hdl.handle.net/2440/21842.
Texte intégralRésumé :
"August 2002"Bibliography: leaves 230-254.
[11], 254 leaves : ill. (some col.), plates (some col.) ; 30 cm.
Field sites and soils from cropping studies in the mid-north of South Australia were used to address questions of soil responses to lime and the influence of acidifying inputs. The study showed that LMWOAs associated with different stubbles can help to ameliorate toxicity through complexation with A1.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002
44
Adcock, Damien Paul. « Soil water and nitrogen dynamics of farming systems on the upper Eyre Peninsula, South Australia ». 2005. http://hdl.handle.net/2440/37810.
Texte intégralRésumé :
In the semi - arid Mediterranean - type environments of southern Australia, soil and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia. The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence. Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other semi - arid environments worldwide. Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less. Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil. The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO [subscript 3] - N at sowing in 2000 and 2002, which conflicts with results from experiments in semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain. Estimates of proportional dependence on N [subscript 2] fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.
45
Thomas, Benjamin Mark. « The role of vesicular-arbuscular mycorrhizal fungi in Linum usitatissimum L. production in Southern Australian soils / Benjamin Mark Thomas ». Thesis, 2001. http://hdl.handle.net/2440/19876.
Texte intégralRésumé :
Bibliography: leaves 106-132.iv, 132 leaves : ill. ; 30 cm.
This project investigated the role of VAM fungi in the growth and nutrition of Linum usitatissimum L. in agricultural soils in southern Australia. It had two general aims: (1) to examine the role of indigenous VAM fungi in the growth and nutrition of linseed in field soil collected near Clare, South Australia; and (2) to examine the effect of VAM fungi on the Zn nutrition of Linola.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2001
46
Adcock, Damien Paul. « Soil water and nitrogen dynamics of farming systems on the upper Eyre Peninsula, South Australia ». Thesis, 2005. http://hdl.handle.net/2440/37810.
Texte intégralRésumé :
In the semi - arid Mediterranean - type environments of southern Australia, soil
and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping
sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia.
The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence.
Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other
semi - arid environments worldwide.
Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent
rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less.
Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil.
The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO₃ - N at sowing in 2000 and 2002, which conflicts with results from experiments in
semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain.
Estimates of proportional dependence on N₂ fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such
estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent
wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited
per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2005.
47
Valizadeh, Reza. « Summer nutrition of sheep based on residues of annual crops and medic pastures / by Reza Valizadeh ». Thesis, 1994. http://hdl.handle.net/2440/21502.
Texte intégralRésumé :
Bibliography: leaves 259-291.xiii, 291 leaves, [8 leaves of col. plates] : ill. (some col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Faculty of Agricultural and Natural Resource Sciences,1994
48
Currie, Dougal Robert. « Soil physical degradation due to drip irrigation in vineyards : evidence and implications ». Thesis, 2007. http://hdl.handle.net/2440/58642.
Texte intégralRésumé :
Drip irrigation is the most common method of water application used in Australian vineyards. However it places physical and chemical stress upon soil structure, which may affect soil physical properties, soil water availability and grapevine functioning. Common soil types within Australian vineyards appear vulnerable to soil degradation and there is emerging evidence of such degradation occurring. Two South Australian vineyards (one located at Nuriootpa in the Barossa Valley, the other in the McLaren Vale winegrowing region) were used to examine evidence of altered soil physical properties due to irrigation. Significantly higher soil strength and lower permeability was found under or near the dripper in irrigated soils. There was also evidence that irrigation increased subsoil bulk density at Nuriootpa. It was uncertain how irrigation caused these changes. While sodicity was present at Nuriootpa, it appeared the physical pressures exerted by irrigation, such as rapid wetting and prolonged wetness, also contributed. To gauge the severity of the degradation at Nuriootpa, a modelling study assessed the impact of higher soil strength and salinity on grapevine transpiration. The SWAP model (Soil- Water-Atmosphere-Plant) was modified and then calibrated using soil moisture data from Nuriootpa. Simulations were conducted for different irrigation regimes and the model output indicated that degradation led to a reduction in cumulative transpiration, which was almost entirely due to higher soil strength. However the reduction was relatively minor and there was evidence of water extraction by roots in all soil layers. Hence the degradation, in terms of higher soil strength and salinity, was not considered a significant management problem in the short - term. Evidence of increased waterlogging and its consequences require further investigation. Roots were observed in soils at Nuriootpa with penetration resistance (PR) much greater than 2 MPa, which was thought to completely impede grapevine root growth. It was hypothesised that roots avoided the physically hostile matrix by using biopores or structural cracks. A pot experiment tested this hypothesis and examined the relationship between soil strength, biopores and root growth for grapevines. Grapevine rootlings (cv. Cabernet Sauvignon) were grown into pots with varying degrees of soil compaction, with and without artificial biopores. No root growth occurred when PR>2 MPa unless biopores were present. Pores also improved root growth in non-compacted soil when PR approached 1 MPa, which suggested biopores influence root growth in soils regardless of compaction levels. Therefore PR should not be the only tool used to examine the rooting-potential of a vineyard soil. An assessment of soil structure, such as biopore density and size, should be incorporated. In drip-irrigated vineyards, there is a possibility that degraded clayey subsoils could be ameliorated by manipulating zones of soil drying. At distances away from the dripper, drying events could generate shrinkage cracks that improve drainage and provide opportunities for root growth. From a practical perspective, drying events could be manipulated by moving the dripper laterally or by changing the irrigation frequency and intensity. The potential of this simple, non-invasive, ameliorative approach was investigated. Large, intact cores were sampled from Nuriootpa subsoil where degradation had been identified. Individual core bulk density was calculated using a formula that was derived by solving two common soil physics equations simultaneously. This proved to be an accurate and non - invasive method. Half the cores were leached with a calcium solution, and the saturated hydraulic conductivity (K [subscript s] ) was measured on all cores before and after drying to a matric potential of -1500 kPa. Soil drying led to a significant increase in K [subscript s], which indicated an improvement in structure through the creation of shrinkage cracks and heaving. Calcium treatment had no impact on K [subscript s], but that could change with more wetting and drying cycles. Results indicated the need for further investigation in the field, where different compressive and tensile forces operate. Harnessing this mechanism may provide an attractive soil management option for growers. The soil physical degradation identified is concerning for sustainable production in irrigated vineyards. Given the sites were representative of typical irrigation practices, such degradation may be widespread. While modelling suggested the impact of higher soil strength and salinity was minimal, these properties should be monitored because they may worsen with continuing irrigation. Furthermore, the impact of irrigation on subsoil permeability needs to be defined more accurately. An increased incidence of waterlogging could significantly restrict production, which was evident when overly wet growing seasons were modelled. If subsoil permeability was found to be significantly lower in irrigated soils, amelioration may be required. In this instance, the use of drying events to generate structure provides an option. Ultimately, the impact of drip irrigation on soil physical quality warrants further attention, and it is imperative to monitor the physical quality of vineyard soils to ensure sustainable production.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007.
49
Harris, Mark Anglin. « The effects of green manure on soil structure in calcareous sodic and non-sodic soils ». 1996. http://web4.library.adelaide.edu.au/theses/09A/09ah315.pdf.
Texte intégral
50
Dennis, Jeremy Ian. « Chocolate spot of faba beans in South Australia ». Thesis, 1991. http://hdl.handle.net/2440/109036.
Texte intégralRésumé :
Entry of inoculum into a crop and disease development in the crop cannot be prevented because spores are airborne and there is a lack of highly resistant varieties. This makes complete control of chocolate spot unlikely. It should however, be possible to improve current levels of disease control through the integration of the factors identified in the studyThesis (M.Ag.Sc.) -- University of Adelaide, Departments of Plant Science and Crop Protection, 1991