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1
Castellazzi, M. S. "Spatio-temporal modelling of crop co-existence in European agricultural landscapes." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/3747.
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The environmental risk of growing genetically modified (GM) crops and particularly the spreading of GM genes to related non-GM crops is currently a concern in European agriculture. Because the risks of contamination are linked to the spatial and temporal arrangements of crops within the landscape, scenarios of crop arrangement are required to investigate the risks and potential coexistence measures. However, until recently, only manual methods were available to create scenarios. This thesis aims to provide a flexible referenced tool to create such scenarios. The model, called LandSFACTS, is a scientific research tool which allocates crops into fields, to meet user-defined crop spatio-temporal arrangements, using an empirical and statistical approach. The control of the crop arrangements is divided into two main sections: (i) the temporal arrangement of crops: encompassing crop rotations as transition matrices (specifically-developed methodology), temporal constraints (return period of crops, forbidden crop sequences), initial crops in fields regulated by temporal patterns (specifically-developed statistical analyses) and yearly crop proportions; and (ii) the spatial arrangements of crops: encompassing possible crops in fields, crop rotation in fields regulated by spatial patterns (specifically-developed statistical analyses), and spatial constraints (separation distances between crops). The limitations imposed by the model include the size of the smallest spatial and temporal unit: only one crop is allocated per field and per year. The model has been designed to be used by researchers with agronomic knowledge of the landscape. An assessment of the model did not lead to the detection of any significant flaws and therefore the model is considered valid for the stated specifications. Following this evaluation, the model is being used to fill incomplete datasets, build up and compare scenarios of crop allocations. Within the GM coexistence context, the model could provide useful support to investigate the impact of crop arrangement and potential coexistence measures on the risk of GM contamination of crops. More informed advice could therefore be provided to decision makers on the feasibility and efficiency of coexistence measures for GM cultivation.
2
Stanley, Jordan. "Yield-Limiting Factors in North Dakota Soybean Fields." Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28382.
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Average soybean [Glycine max (L.) Merrill] yields in North Dakota remain below north central USA averages, and crop yield potentials. The effect of planting date (PD), cultivar relative maturity (RM), and seeding rate (SR), on yield, were evaluated in 821 producer fields in 2014-2016 seasons. Crop management varied by location. State average PD was 19 May, and planting after 1 May reduced yield average 0.4% d-1. Planting a cultivar with 0.1 RM earlier than recommended reduced yield by 1.3%. Producers estimated seedling mortality at 10%; when observed, it was 12.3%. An additional 7.9% reduction of established population occurred in-season. In-season plant reductions of 4.5% were also observed in research trials. North Dakota producers should plant closer to 1 May if conditions are favorable, select latest-maturing cultivars adapted for area, maximize established plant population relative to seeding rate, and determine causes of in-season plant reductions to adapt management practices if necessary.
3
Fletcher, Penny Hazel. "The pollination of four wild plants species in crop fields." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533764.
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4
Shaw, Gordon W. "Oak regeneration in former crop fields in the Missouri river floodplan /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426103.
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5
Gilbert, J. "The population dynamics of field pansy (Viola arvensis) and red deadnettle (Lamium purpureum) in winter cereal and oilseed rape fields." Thesis, Keele University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382899.
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6
Coyne, Daniel L. "Epidemiology and crop loss assessment of rice nematodes in West Africa." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299612.
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7
Kim, Dong-Gill. "Nitrous oxide and methane fluxes in riparian buffers and adjacent crop fields." [Ames, Iowa : Iowa State University], 2008.
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8
Reynolds, William Casey. "Establishment Rates and Growth Characteristics of Six Bermudagrass Cultivars for use on Athletic Fields and Golf Course Fairways." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-12112002-145750/.
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Bermudagrass (Cynodon spp.) is the primary choice for athletic fields and golf course fairways in the southeastern United States. Its superior heat and drought tolerance as well as excellent recuperative capacity allow it to withstand many of the stresses often associated with recreational turf. There are several new cultivars on the market with little available information regarding their performance. Six cultivars of bermudagrass, ?TifSport?, ?Tifway?, ?GN-1?, ?Quickstand?, ?Navy Blue?, and ?Tifton 10? were established by sprigs on a Candor sand (Sandy, siliceous, thermic, Arenic Paleudult) at the rate of 0.1m3/100m2 on 28 June 2001 at the Sandhills Research Station in Jackson Springs, NC. During year one of the study, data were taken on establishment, rooting, disease incidence, fall color, and spring green-up of each of the six bermudagrasses. Tifton 10 demonstrated the ability to establish faster than all other cultivars based on its ranking on all observation dates followed by Quickstand and GN-1, which had five and four top rankings, respectively. No differences in rooting density were found among the six cultivars. Navy Blue exhibited significantly more dollar spot (Sclerotinia homoeocarpa F.T. Bennett) incidence than all other cultivars, while GN-1 had significanctly higher incidence of Large patch (Rhizoctonia solani). During April 2002, 10.8 cm diameter plugs were taken from the field plots for the low temperature study. Sixty stolons per cultivar were excised from the plugs and placed into a Low Temperature Stress Simulator (LTSS) where they were exposed to four different temperatures of 2oC, 0oC, ?2oC, and -4 oC for a period of 24 hr. No significant differences were found among cultivars in their ability to tolerate low temperatures, but mortality did increase as temperature decreased. After the field plots had achieved one year of growth, data were taken on growth characteristics such as root and rhizome mass, recuperative potential, surface hardness, seedhead production, and overall quality. No significant differences were found in root or rhizome mass among the six cultivars. Quickstand produced a harder surface than all other cultivars on 24 July, while Tifton 10, GN-1, and TifSport were the softest. TifSport consistently produced the highest turf quality of the six cultivars followed by Tifway, GN-1, and Navy Blue. Quickstand and Tifton 10 had the poorest quality over four observation dates, primarily due to their coarse texture and off-green color. Differences among these six bermudagrass cultivars imply that they may not all be suitable for the same situation. Turfgrass managers can match this data to their intended use and more accurately choose which cultivar will perform best under their specific conditions.
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Dey, Pannalal. "Search for agriculturally important microorganisms from soils of river basins, forests and crop fields in the terai-dooars of North Bengal and analysis of their diversity." Thesis, University of North Bengal, 2011. http://hdl.handle.net/123456789/1423.
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10
Chapkowski, Andrew J. "Geographical distribution of pediobius foveolatus in New Jersey soybean fields to control the Mexican bean beetle population." Diss., Maryville, Mo. : Northwest Missouri State University, 2008. http://www.nwmissouri.edu/library/theses/ChapkowskiAndrew/index.htm.
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Thesis (M.S.)--Northwest Missouri State University, 2008.<br>The full text of the thesis is included in the pdf file. Title from title screen of full text.pdf file (viewed on July 25, 2008) Includes bibliographical references.
11
Caiado, Marco Aurelio. "Modeling Fate and Transport of Nitrogen and Phosphorus in Crop Fields Under Tropical Conditions." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28848.
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Modeling is a very important tool for developing nonpoint source (NPS) pollution control plans. Current NPS models were developed for temperate conditions and, thus, do not appropriately represent tropical conditions. The objective of this research was to develop or adapt a nonpoint source pollution model to simulate transformations and losses of nitrogen (N) and phosphorus (P) in leachate and runoff from crop fields under humid tropical conditions.
An extensive literature synthesis identified appropriate relationships for representing hydrologic and NPS processes in the tropics, as well as soil and climate conditions that differ from temperate conditions and impact NPS pollution. The GLEAMS model was selected for adaptation. Changes to the model included calculation of potential evapotranspiration (ET); changes in initial and default values of N and P pools, C:N ratio of soil organic matter, and soil P sorption; changes in simulation of transformations between N and P pools, along with the effect of temperature; and inclusion of a nitrate retardation factor (Ncrit) and pH in the calculation of N transformation and movement.
The adapted model, called TROPGLEAMS, was evaluated through model verification, application, and sensitivity analysis. Model verification comprised a mass balance of nutrients and analysis of the variation of variable values in time. Model validation included application of the GLEAMS and TROPGLEAMS to three sites in Brazil: a set of lysimeters planted with sugarcane in Piracicaba, SP; a set of plots planted with sugarcane in Piracicaba; and a set of plots planted in a wheat-soybean rotation in Lages, SC. Model sensitivity to temperature, Ncrit and pH were evaluated in the sensitivity analysis.
Model evaluation indicated that TROPGLEAMS is more accurate than GLEAMS in simulating fate and transport of nutrients under tropical conditions. Prediction of actual ET, effect of tillage on losses of N and P in runoff, and N and P kinetics was improved with TROPGLEAMS compared to GLEAMS. However, based on data from the Lages study, TROPGLEAMS did not simulate losses of nutrients in runoff well. Improvements in the model, especially related to losses in runoff, and application of TROPGLEAMS to different areas of the humid tropics are recommended.<br>Ph. D.
12
Pelcat, Yann S. "Soil landscape characterization of crop stubble covered fields using Ikonos high resolution panchromatic images." Thesis, Winnipeg : University of Manitoba, 2006. http://www.collectionscanada.ca/obj/s4/f2/dsk3/MWU/TC-MWU-224.pdf.
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Thesis (M.Sc.)--University of Manitoba, 2006.<br>A thesis submitted to the Faculty of Graduate Studies in partial fulfillment of the requirements for the degree of Master of Science, Department of Soil Science. Includes bibliographical references.
13
Coulombe, Anne-Marie. "Evaluation of the seed bank content as a predictor of weed infestations in crop fields." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21063.pdf.
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14
Karimi-Zindashty, Yousef. "Application of hyperspectral remote sensing in stress detection and crop growth modeling in corn fields." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85560.
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This study used hyperspectral data to determine nitrogen, weed, and water stresses in a corn (Zea mays L.) field in southwestern Quebec, and incorporated these data in crop growth models for better crop growth simulation under stressful conditions.<br>In 2000, aerial hyperspectral images (72 wavebands, ranging from 407 to 949 nm) were acquired, and analyzed using a stepwise approach to identify wavebands useful in detecting weed and nitrogen stresses. Discriminant analysis (DA) was used to classify different weed and nitrogen treatments and their combinations. This analysis showed greater classification accuracy (nearly 75%) than those obtained with artificial neural networks (58%) or decision tree algorithms (60%), at the initial growth stages, the time when remedial actions are most needed to alleviate weed and nitrogen stresses.<br>To explore the possibility of improving nitrogen stress detection in corn in the presence of a confounding water stress, ground-based 2151 narrow-waveband reflectance values (350 to 2500 nm), were collected in 2002. Using DA with the chosen subset of narrow-wavebands, a classification accuracy of greater than 95% was obtained.<br>For crop growth monitoring, the STICS model was evaluated for yield and biomass estimation in cornfields under different stressful growth conditions using the data collected from 2000 to 2002. Measured yield, biomass, and leaf area index (LAI) were used for both calibration and validation of the model. High correlation coefficients between the measured and estimated grain yield (0.96), biomass (0.98), and LAI (0.93) indicated that the model has good potential in the simulation of corn growth. The model was also linked with LAI values estimated from the hyperspectral observations using the Support Vector Machines technique. Coupling STICS with remote sensing resulted in an overall improvement in the simulation of corn yield (6.3%) and biomass (3.7%).<br>A new approach was developed to apply crop growth models for yield estimation in weedy areas. The proposed method first corrects the measured/estimated LAI values in weed infested fields for weed effect, and then uses the corrected LAI values as input to the crop growth model. The results showed that the crop yield and biomass predictions were correctly simulated by this method.*<br>*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).
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Schwer, Laura Mary Jane. "SMALL MAMMAL POPULATIONS IN SWITCHGRASS STANDS MANAGED FOR BIOMASS PRODUCTION COMPARED TO HAY AND CORN FIELDS IN KENTUCKY." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/138.
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Switchgrass (Panicum virgatum), a native warm-season grass, has been investigated as a renewable energy crop that may provide viable wildlife habitat. This study investigated small mammal populations in switchgrass, hay, and corn to assess the relative habitat quality. Four, three-night trapping sessions were conducted at four locations in Kentucky using Sherman livetraps. Trapping occurred in spring (before first hay harvest), summer, fall (before switchgrass and corn harvest), and winter (post-harvest). Relative abundance of small mammals, calculated using a capture per unit effort index (per 100 trapnights), and mean taxonomic richness were used to compare habitats. Switchgrass had a significantly greater mean taxonomic richness than hay but not corn; however, four genera were captured in switchgrass and only two in corn. Switchgrass had a greater relative abundance of small mammals than hay during the summer, and corn and hay during the fall. Vegetative cover was positively correlated with relative abundance of small mammals. No-till corn and three year old switchgrass had a greater relative abundance of small mammals than conventionally tilled corn and two year old switchgrass, respectively. In conclusion, switchgrass stands managed as a renewable energy crop has the potential to be viable wildlife habitat for some small mammal species.
16
Capiral, Mary Joy Josephine M. "Measurements of ammonia and nitrous oxide emissions from potato fields in Central Washington using differential optical absorption spectroscopy (DOAS), tracer dispersion, and static chamber methods." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/m_capiral_042309.pdf.
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Thesis (M.S. in environmental engineering)--Washington State University, May 2009.<br>Title from PDF title page (viewed on May 21, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 87-91).
17
Alghamdi, Rashad Saeed. "Soil Warming and Drying and the Consequence to Crop Yields among Conservation Tillage Practices in Frigid Corn-Soybean Fields." Thesis, North Dakota State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10605433.
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<p> Concerns over delayed soil warming and drying have hindered adoption of conservation tillage practices in frigid environments. Our objectives were to evaluate the effects of chisel plow (CP), vertical tillage (VT), strip tillage with coulters (STC), and strip tillage with shanks (STS) on soil warming and drying and their potential consequences to crop yields. A two-year study was conduct at three full-scale, producer-managed, corn-soybean fields in the Red River Valley of eastern North Dakota and western Minnesota. Tillage treatments were assessed to measure crop residue cover, soil temperatures, soil volumetric water contents, crop yields, and other metrics. Our study indicated significant differences for many soil physical and chemical parameters, but little to none for soil warming and crop yields. Yield differences were attributed to varying fertilizer management practices, timing, and application method. These findings emphasize the importance of field management practices that compliment conservation tillage for obtaining competitive crop yields. </p><p>
18
Alghamdi, Rashad Saeed. "Soil Warming and Drying and the Consquence to Crop Yields among Conservation Tillage Practices in Frigid Corn-Soybean Fields." Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28405.
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Concerns over delayed soil warming and drying have hindered adoption of conservation tillage practices in frigid environments. Our objectives were to evaluate the effects of chisel plow (CP), vertical tillage (VT), strip tillage with coulters (STC), and strip tillage with shanks (STS) on soil warming and drying and their potential consequences to crop yields. A two-year study was conduct at three full-scale, producer-managed, corn-soybean fields in the Red River Valley of eastern North Dakota and western Minnesota. Tillage treatments were assessed to measure crop residue cover, soil temperatures, soil volumetric water contents, crop yields, and other metrics. Our study indicated significant differences for many soil physical and chemical parameters, but little to none for soil warming and crop yields. Yield differences were attributed to varying fertilizer management practices, timing, and application method. These findings emphasize the importance of field management practices that compliment conservation tillage for obtaining competitive crop yields.
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Kenduiywo, Benson Kipkemboi [Verfasser], Matthias [Akademischer Betreuer] Becker, Uwe [Akademischer Betreuer] Soergel, and Eichhorn [Akademischer Betreuer] Andreas. "Spatial-temporal Dynamic Conditional Random Fields crop type mapping using radar images / Benson Kipkemboi Kenduiywo ; Matthias Becker, Uwe Soergel, Eichhorn Andreas." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1117135209/34.
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20
Kapal, Debbie B. "Influence of a legume green manure crop on barley straw/stubble decomposition, and soil nitrogen retention and availability." Lincoln University, 2008. http://hdl.handle.net/10182/701.
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The incorporation of cereal straw/stubble often immobilises nitrogen (N). This can help conserve N in soil in organic forms, thus reducing loss through leaching over dormant winter periods. However, N-depressions that arise during decomposition can reduce crop yield. The inclusion of a legume green manure can supply fixed-N, thus alleviating the low N availability to crops. In this study, the effect of lupin (Lupinus angustifolius L.) green manure incorporation on barley (Hordeum vulgare L.) straw/stubble decomposition, and N availability was investigated. A field experiment was used to determine the effects of the green manure on decomposition. Decomposition of straw/stubble was monitored using the litterbag technique. Following green manure incorporation, soil cores were incubated in a glasshouse to determine mineral-N availability. Though not significant, the inclusion of lupin green manure seemed to increase the decomposition of straw/stubble during the growth period, then slowing it after its incorporation at 110 d. This was described by a logarithmic pattern of loss of - 4.97 g AFDW residue day⁻¹, with 60% remaining after 140 d. Treatments without lupin had a linear decomposition of - 0.12 g AFDW residue day⁻¹, with 49% remaining after 140 d. The loss of cellulose confirmed the differences in decomposition with the inclusion of lupin resulting in 2.79% less cellulose remaining in straw/stubble after 140 d compared to its exclusion. Lupin significantly increased pot oat N uptake and DM yield by 55 % and 46 %, respectively, compared to its exclusion. However, this effect was not observed in field sown wheat yields and the soil mineral-N measurements made. This study showed that the potential of lupin to increase straw/stubble decomposition by improving the retention and availability of N, leading to long-term yield benefits, needed further investigation.
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Varella, Alexandre Costa. "Modelling lucerne (Medicago sativa L.) crop response to light regimes in an agroforestry system." Lincoln University, 2002. http://hdl.handle.net/10182/1477.
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The general goal of this research was to understand the agronomic and physiological changes of a lucerne crop in distinct physical radiation environments and to verify the potential of lucerne to grow under shaded conditions. To achieve this, the research was conducted in four main steps: (i) firstly, experimental data collection in the field using two artificial shade materials (shade cloth and wooden slats) under inigated and non-irrigated conditions; (ii) a second experiment with data collection in a typical temperate dryland agroforestry area under non-irrigated conditions; (iii) generation of a light interception sub-model suitable for shaded crops and (iv) a linkage between the light interception sub-model and a canopy photosynthesis model for agroforestry use. In experiments 1 and 2, lucerne crop was exposed to 6 different light regimes: full sunlight (FS), shade cloth (FS+CL), wooden slats (FS+SL), trees (T), trees+cloth (T +CL) and trees+slats (T+SL). The FS+SL structure produced a physical radiation environment (radiation transmission, radiation periodicity and spectral composition) that was similar to that observed in the agroforestry site (f). The mean annual photosynthetic photon flux density (PPFD) was 41 % under the FS+CL, 44% under FS+SL and 48% under T compared with FS in clear sky conditions. Plants were exposed to an intermittent (sun/shade) regime under both FS+SL and T, whereas under FS+CL the shaded light regime was continuous. The red to far-red (RIFR) ratio measured during the shade period under the slats was 0.74 and under the trees was 0.64. However, R/FR ratio increased to 1.26 and 1.23 during the illuminated period under FS+SL and T, respectively, and these were equivalent to the ratio of 1.28 observed under the FS+CL and 1.31 in FS. The radiation use efficiency (RUE) of shoots increased under the 5 shaded treatments compared with full sunlight. The pattern of radiation interception was unchanged by radiation flux, periodicity and spectral composition and all treatments had a mean extinction coefficient of 0.82. However, the magnitude of the decrease in canopy growth was less than those in PPFD transmissivity. The mean lucerne annual dry matter (DM) yield was 17.5 t ha⁻¹ in FS and 10 t ha⁻¹ under the FS+CL, FS+SL and T regimes. This declined to 3.4 t DM ha⁻¹ under T+CL (22% PPFD transmissvity) and 4.1 t DM ha⁻¹ under T+SL (23% transmissivity). A similar pattern of response was observed for leaf net photosynthesis (Pn) rates under the shade treatments compared with full sun. In addition, spectral changes observed under the trees and slats affected plant motphology by increasing the number of long stems, stem height and internode length compared with full sunlight. Thus, there were two main explanations for the increase in RUE under shade compared with full sun: (i) preferential partition of assimilates to shoot rather than root growth and/or (ii) leaves under shade were still operating at an efficient part of the photosynthetic light curve. The changes proposed for the canopy Pn model were appropriate to simulate the radiation environment of an agroforestry system. However, the model underestimated DM yields under the continuous and intermittent shade regimes. These were considered to be mainly associated with plant factors, such as overestimation in maintenance respiration and partitioning between shoots and roots in shade and the intermittency light effect on leaf Pn rates. Further investigation in these topics must be addressed to accurately predict crop yield in agroforestry areas. Overall, the lucerne crop responded typically as a sun-adapted plant under shade. It was concluded that lucerne yield potential to grow under intermediate shade was superior to most of C3 pastures previously promoted in the literature.
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Knight, Kris William. "Effectiveness of naturally-occurring riparian forest buffers and grass filter strips at buffering concentrated flow from row crop fields to streams in northeast Missouri." [Ames, Iowa : Iowa State University], 2007.
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Ford, R. J. "The effect of shading and crop load on flavour and aroma compounds in Sauvignon blanc grapes and wine." Lincoln University, 2007. http://hdl.handle.net/10182/498.
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The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored. Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant factor in determining timing of grape physiological ripeness as expressed by °Brix over other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine) and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must. After wine processing lower malic acid concentrations in wines made from 100% exposed fruit became evident in lower wine titratable acidity but showed no influence on wine pH. Bentonite addition to wines had a small but statistically significant influence on wine by reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries. The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine quality.
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Stark, Christine H. "Effects of long- and short-term crop management on soil biological properties and nitrogen dynamics." Lincoln University, 2005. http://hdl.handle.net/10182/30.
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To date, there has been little research into the role of microbial community structure in the functioning of the soil ecosystem and on the links between microbial biomass size, microbial activity and key soil processes that drive nutrient availability. The maintenance of structural and functional diversity of the soil microbial community is essential to ensure the sustainability of agricultural production systems. Soils of the same type with similar fertility that had been under long-term organic and conventional crop management in Canterbury, New Zealand, were selected to investigate relationships between microbial community composition, function and potential environmental impacts. The effects of different fertilisation strategies on soil biology and nitrogen (N) dynamics were investigated under field (farm site comparison), semi-controlled (lysimeter study) and controlled (incubation experiments) conditions by determining soil microbial biomass carbon (C) and N, enzyme activities (dehydrogenase, arginine deaminase, fluorescein diacetate hydrolysis), microbial community structure (denaturing gradient gel electrophoresis following PCR amplification of 16S and 18S rDNA fragments using selected primer sets) and N dynamics (mineralisation and leaching). The farm site comparison revealed distinct differences between the soils in microbial community structure, microbial biomass C (conventional>organic) and arginine deaminase activity (organic>conventional). In the lysimeter study, the soils were subjected to the same crop rotation (barley (Hordeum vulgare L.), maize (Zea mais L.), rape (Brassica napus L. ssp. oleifera (Moench)) plus a lupin green manure (Lupinus angustifolius L.) and two fertiliser regimes (following common organic and conventional practice). Soil biological properties, microbial community structure and mineral N leaching losses were determined over 2½ years. Differences in mineral leaching losses were not significant between treatments (total organic management: 24.2 kg N ha⁻¹; conventional management: 28.6 kg N ha⁻¹). Crop rotation and plant type had a larger influence on the microbial biomass, activity and community structure than fertilisation. Initial differences between soils decreased over time for most biological soil properties, while they persisted for the enzyme activities (e.g. dehydrogenase activity: 4.0 and 2.9 µg g⁻¹ h⁻¹ for organic and conventional management history, respectively). A lack of consistent positive links between enzyme activities and microbial biomass size indicated that similarly sized and structured microbial communities can express varying rates of activity. In two successive incubation experiments, the soils were amended with different rates of a lupin green manure (4 or 8t dry matter ha⁻¹), and different forms of N at 100 kg ha⁻¹ (urea and lupin) and incubated for 3 months. Samples were taken periodically, and in addition to soil biological properties and community structure, gross N mineralisation was determined. The form of N had a strong effect on microbial soil properties. Organic amendment resulted in a 2 to 5-fold increase in microbial biomass and enzyme activities, while microbial community structure was influenced by the addition or lack of C or N substrate. Correlation analyses suggested treatment-related differences in nutrient availability, microbial structural diversity (species richness or evenness) and physiological properties of the microbial community. The findings of this thesis showed that using green manures and crop rotations improved soil biology in both production systems, that no relationships existed between microbial structure, enzyme activities and N mineralisation, and that enzyme activities and microbial community structure are more closely associated with inherent soil and environmental factors, which makes them less useful as early indicators of changes in soil quality.
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Zhou, Shuang. "EVALUATING SOIL PHYSICAL AND CHEMICAL PROPERTIES FOLLOWING ADDITION OF NON-COMPOSTED SPENT COFFEE AND TEA FOR ATHLETIC FIELDS." UKnowledge, 2017. https://uknowledge.uky.edu/pss_etds/96.
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Physical and chemical properties of non-composted spent coffee (CF) and tea (T) suggest they may have applications as soil amendments for improving poor soils. Studies were conducted to determine 1) the effect of amendments on grass growth and soil properties, 2) the effect of incorporation versus surface application of amendments on soil properties, and 3) the effect of amendment application frequency on grass growth and soil properties. In the first study, amendments were mixed with sand and planted to bermudagrass. Treatments included CF, T, and peat moss (PM) mixed with sand, and 100% sand as a control. In the second study, amendments were topdressed onto a sand base with different timings. Pots were either aerified or not. Treatments included T, CF, PM, and a control. Nutrient contents and soil CEC and OM under CF and T treatments were equivalent to or greater than PM treatments. Tea showed comparable grass cover to the PM treatment, while CF showed an inhibitory effect to grass growth in the first year of the study. Aerification showed no benefit. Additionally, a field study was conducted to evaluate CF and T on surface hardness, VWC, and quality after trafficking. Differences were not observed among treatments.
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Leeks, C. R. F. "Determining seed vigour in selected Brassica species." Lincoln University, 2006. http://hdl.handle.net/10182/1274.
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Variables for the accelerated ageing (AA) test, methods for reducing fungal contamination during the AA test, using the conductivity test as a vigour test, the effect of seed size on seed vigour and the relationship between laboratory test results and field perfonnance in selected Brassica spp were investigated. In the first experiment, three seed lots of turnip rape hybrid (B. rapa x campestris), turnip (B. campestris) and forage rape (B. napus); and seven seed lots of Asian rape (B. napus), six seed lots of Asian kale (B. oleraceae var. alboglabra L.) and five seed lots of choisum (B. rapa var. pekinensis) with germinations above 90% were aged at two different temperatures (41 and 42°C ± 0.3°C) and three ageing times (24, 48 and 72 ± 15 minutes). The second experiment was divided into three sections. In the first, the same seed lots and species were aged at one temperature (41°C) and time (72 h), but either 40 ml of saturated salts; KCl (83%RH), NaCl (76%RH), NaBr (55%RH); or distilled water (96%RH) were used as the ageing solutions. In the second, one turnip rape hyprid seed lot was aged at three temperatures (41, 42 and 45°C) and two times (72 and 96h), again using the three saturated salts and distilled water as ageing solutions. In the third, three turnip rape hybrid seed lots and three Asian kale seed lots were surface sterilised (1 % sodium hypochlorite) prior to ageing at one temperature (41°C) and time (72 h). In the third experiment, the same species and seed lots used in experiment one at their original seed moisture content (SMC) were tested for conductivity after soaking in deionised water for 4, 8, 12, 16, 20 and 24 h. They were then re-tested after the SMC had been adjusted to 8.5%. In the fourth experiment, three seed lots of forage rape and three seed lots of Asian kale were graded into three seed size categories; large (retained on a 2.0 mm screen), medium (retained on a 1.7 mm screen) and small (passed through a 1.7 mm screen). Graded seeds were then tested for standard germination, AA (41°C/48 h) and conductivity (measured at 16 and 24 h). In the final experiment, the relationships between laboratory tests for the six species (each consisting of three seed lots), field emergence from three sowings, and cold room emergence were evaluated. Both time and temperature influenced post-AA germination. Increasing the ageing period from 48 to 72 hours at 41°C, and 24 to 48 hours at 42°C resulted in decreased mean germination percentage for all species but not always clear separation of seed lots. While there were sometimes few differences between ageing at 41°C and 42°C, the former is preferred because it is already the temperature used for other species. For Asian rape, choisum and turnip, the previously recommended testing conditions of 41°C/72 h provided good seed lot separation, but for Asian kale and turnip rape hybrid, AA testing at 41°C/48 h provided better results. Seed moisture content after ageing ranged from 29-37% depending on species. Fungal growth on seeds during the ageing period appeared to reduce post-ageing germination in some seed lots . Substituting saturated salts for distilled water did not stress seed lots in the AA test, due to the lowered RH%, the exception being seed lots 1210 and 1296. For forage and Asian species, seed lot germination mostly remained above 90% when aged for 72 h at lowered RH%. Increasing the ageing duration from 72 to 96 hours resulted in some decreases in post-AA germination but no clear separation of seed lots. Surface sterilising the seeds prior to the AA test resulted in a lower incidence of contaminant fungi which was associated with a lower percentage of abnormal seedlings. The conductivity test was mostly able to identify vigour differences among forage and Asian vegetable brassica seed lots. Differences in conductivity readings were observed among seed lots in all species. Increasing the period of imbibition resulted in increased conductivity from most seed lots but radicle emergence occurred after 16-20 h of imbibition. Variation was observed in the time to reach 95% maximum of the imbibition curve for most species. Conductivity readings at 16 h would avoid possible influences of radicle emergence on results. Adjusting the SMC to 8.5% resulted in reduced variation in conductivity among replicates of seed lots, due to a reduction in imbibition damage. Seed size had a significant effect on both post-AA germination and conductivity results. In forage rape, large size seeds had higher post-AA germination cf. medium cf. small size seeds. In Asian kale, large size seeds had higher post-AA germination compared with small size seeds. For both forage rape and Asian kale, large size seeds had lower conductivity readings cf. small size seeds. The correlation analyses demonstrated significant relationships between AA testing and field emergence parameters (percentage emergence, emergence index and emergence rate). Significant relationships were also observed between conductivity testing and these field emergence parameters. Based on the correlation analysis, AA testing at 41°C/48 hand/or 42°C/48 h could be recommended to be used as an AA test for turnip and Asian rape; and 41°C/48 hand/or 41°C/72 h for Asian kale and choisum. Based on the correlation analysis, conductivity testing at 16 h can be used to predict the field emergence potential of forage and Asian vegetable seed lots. Vigour tests were consistently able to provide better indicators of field perfonnance than the standard germination test, although these relationships did vary with the different field sowings.
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Moot, Derrick J. "Harvest index variability within and between field pea (Pisum sativum L.) crops." Lincoln University, 1993. http://hdl.handle.net/10182/1285.
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The association between individual plant performance and seed yield variability within and between field pea crops was investigated. In 1988/89 six F8 genotypes with morphologically distinct characteristics were selected from a yield evaluation trial. Analysis of the individual plant performance within these crops indicated an association between low seed yields and the location and dispersion of plant harvest index (PHI) and plant weight (PWT) distributions. The analyses also showed there was a strong linear relationship between the seed weight (SWT) and PWT of the individual plants within each crop, and that the smallest plants tended to have the lowest PHI values. A series of 20 simulations was used to formalize the relationships between SWT, PWT and PHI values within a crop into a principal axis model (PAM). The PAM was based on a principal axis which represented the linear relationship between SWT and PWT, and an ellipse which represented the scatter of data points around this line. When the principal axis passed through the origin, the PHI of a plant was independent of its PWT and the mean PHI was equal to the gradient of the axis. However, when the principal axis had a negative intercept then the PHI was dependent on PWT and a MPW was calculated. In 1989/90 four genotypes were sown at five plant populations, ranging from 9 to 400 plants m⁻². Significant seed and biological yield differences were detected among genotypes at 225 and 400 plants m⁻². The plasticity of yield components was highlighted, with significant genotype by environment interactions detected for each yield component. No relationship was found between results for yield components from spaced plants and those found at higher plant populations. The two highest yielding genotypes (CLU and SLU) showed either greater stability or higher genotypic means for PHI than genotypes CVN and SVU. Despite significant skewness and kurtosis in the SWT, PWT, and PHI distributions from the crops in this experiment, the assumptions of the PAM held. The lower seed yield and increased variability in PHI values for genotype CVN were explained by its higher MPW and the positioning of the ellipse closer to the PWT axis intercept than in other genotypes. For genotype SVU, the lower seed yield and mean PHI values were explained by a lower slope for the principal axis. Both low yielding genotypes were originally classified as having vigorous seedling growth and this characteristic may be detrimental to crop yields. A method for selection of field pea genotypes based on the PAM is proposed. This method enables the identification of weak competitors as single plants, which may have an advantage over vigorous plants when grown in a crop situation.
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Klatt, Björn Kristian Verfasser], Teja [Akademischer Betreuer] Tscharntke, Stefan [Akademischer Betreuer] Vidal, and Alexandra-Maria [Akademischer Betreuer] [Klein. "Bee pollination of strawberries on different spatial scales - from crop varieties and fields to landscapes / Björn Kristian Klatt. Gutachter: Teja Tscharntke ; Stefan Vidal ; Alexandra-Maria Klein. Betreuer: Teja Tscharntke." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044173440/34.
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Tolomio, Massimo. "Evaluation of long-term water management strategies for saving water and reducing nitrogen and phosphorus losses from agricultural fields: controlled drainage and surface flow constructed wetland case studies in Venice Lagoon drainage basin." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421846.
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In in contesto di carenza idrica e di inquinamento delle acque superficiali causato dalle attività agricole, devono essere identificate nuove pratiche di gestione delle risorse idriche che rispondano a queste problematiche e possano essere utilizzate in diversi ambienti.
Il bacino idrografico della Laguna di Venezia (nell'Italia nord-orientale) è un'area sensibile all'inquinamento delle acque superficiali. La prevalenza di terreni pianeggianti e la presenza di una falda freatica superficiale, tuttavia, suggeriscono condizioni idonee per la realizzazione di due pratiche di gestione idrica per la riduzione dei carichi di N e P provenienti dalle aree agricole: il drenaggio controllato (controlled drainage: CD) e le wetland artificiali a flusso superficiale (surface flow constructed wetlands: SFCWs). Il monitoraggio di lungo periodo delle performance di queste pratiche è necessario per fornire risultati di validità generale, che non siano condizionati dalla variabilità meteorologica annuale.
Questo lavoro valuta le performance di un sistema di CD e di SFCW in un esperimento di lungo periodo. Il CD è stato monitorato durante i periodi 1995-2002 e 2006-2013, in termini di bilancio idrico e di resa delle colture, e dal 2007 al 2013 anche per le perdite di N e P. La SFCW è stata monitorata dal 2007 al 2013 per la riduzione dei carichi di N e P.
Il CD ha permesso di ridurre i deflussi idrici del 69% e ha determinato un aumento complessivo della resa di granella di mais del 26,3%, e della resa di mais da insilato del 4,0%. Le perdite di NO3-N e PO4-P nelle acque superficiali sono state ridotte rispettivamente del 92% e del 65%.
La SFCW ha mostrato tassi di rimozione annui apparenti dell'83% e del 79% rispettivamente per NO3-N e N totale, e del 48% e del 67% rispettivamente per PO4-P e P totale.
Sia il CD che la SFCW si sono rivelati efficaci nel ridurre i carichi inquinanti di N e P, ed il CD ha anche contribuito ad aumentare la resa delle colture attraverso il risparmio idrico. Per questi motivi, l'applicazione di queste due pratiche di gestione idrica è da prendersi in considerazione in questo ambiente.<br>In the context of increasing water scarcity and surface water pollution caused by agricultural activities, new water management practices that tackle these issues and that could be used in different environments should be identified.
The Venice Lagoon drainage basin (in north-eastern Italy) is a sensitive area to surface water pollution. The prevalence of flat lands and the presence of shallow phreatic groundwaters, however, create suitable conditions for the implementation of two water management practices that can reduce N and P loads coming from agricultural fields: controlled drainage (CD) and surface flow constructed wetlands (SFCWs). Long-term monitoring of the performances of these practices is required to provide sound results that are not contingent on annual weather variability.
This work evaluates the performances of a CD and SFCW system in a long-term experiment. CD was monitored during the periods 1995-2002 and 2006-2013 for water balance and crop yield, and from 2007 to 2013 for N and P losses. The SFCW was monitored from 2007 to 2013 for N and P removal loads.
CD permitted to reduce water outflows of 69%, and provided an overall increase in maize grain yield of 26.3% and in silage maize yield of 4.0%. NO3-N and PO4-P losses to surface waters were reduced by 92% and 65%, respectively.
The SFCW showed annual apparent removal rates of 83% and 79% respectively for NO3-N and total N, and of 48% and 67% respectively for PO4-P and total P.
Both CD and SFCW proved effective in reducing N and P loads, and CD helped increasing crop yield through water saving. For these reasons, the application of these two water management practices is advisable in this environment.
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Bithell, S. L. "An evaluation of Solanum nigrum and S. physalifolium biology and management strategies to reduce nightshade fruit contamination of process pea crops." Lincoln University, 2004. http://hdl.handle.net/10182/1160.
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The contamination of process pea (Pisum sativum L.) crops by the immature fruit of black nightshade (Solanum nigrum L.) and hairy nightshade (S. physalifolium Rusby var. nitidibaccatum (Bitter.) Edmonds) causes income losses to pea farmers in Canterbury, New Zealand. This thesis investigates the questions of whether seed dormancy, germination requirements, plant growth, reproductive phenology, or fruit growth of either nightshade species reveal specific management practices that could reduce the contamination of process peas by the fruit of these two weeds. The seed dormancy status of these weeds indicated that both species are capable of germinating to high levels (> 90%) throughout the pea sowing season when tested at an optimum germination temperature of 20/30 °C (16/8 h). However, light was required at this temperature regime to obtain maximum germination of S. nigrum. The levels of germination in the dark at 20/30 °C and at 5/20 °C, and in light at 5/20 °C, and day to 50 % germination analyses indicated that this species cycled from nondormancy to conditional dormancy throughout the period of investigation (July to December 2002). For S. physalifolium, light was not a germination requirement, and dormancy inhibited germination at 5/20 °C early in the pea sowing season (July and August). However, by October, 100% of the population was non-dormant at this test temperature. Two field trials showed that dark cultivation did not reduce the germination of either species. Growth trials with S. nigrum and S. physalifolium indicated that S. physalifolium, in a non-competitive environment, accumulated dry matter at a faster rate than S. nigrum. However, when the two species were grown with peas there was no difference in dry matter accumulation. Investigation of the flowering phenology and fruit growth of both species showed that S. physalifolium flowered (509 °Cd, base temperature (Tb) 6 °C) approximately 120 °Cd prior to S. nigrum (633 °Cd). The fruit growth rate of S. nigrum (0.62 mm/d) was significantly faster than the growth rate of S. physalifolium (0.36 mm/d). Because of the earlier flowering of S. physalifolium it was estimated that for seedlings of both species emerging on the same date that S. physalifolium could produce a fruit with a maximum diameter of 3 mm ~ 60 °Cd before S. nigrum. Overlaps in flowering between peas and nightshade were examined in four pea cultivars, of varying time to maturity, sown on six dates. Solanum physalifolium had the potential to contaminate more pea crops than S. nigrum. In particular, late sown peas were more prone to nightshade contamination, especially late sowings using mid to long duration pea cultivars (777-839 °Cd, Tb 4.5 °C). This comparison was supported by factory data, which indicated that contamination of crops sown in October and November was more common than in crops sown in August and September. Also, cultivars sown in the later two months had an ~ 100 °Cd greater maturity value than cultivars sown in August and September. Nightshade flowering and pea maturity comparisons indicated that the use of the thermal time values for the flowering of S. nigrum and S. physalifolium can be used to calculate the necessary weed free period required from pea sowing in order to prevent the flowering of these species. The earlier flowering of S. physalifolium indicates that this species is more likely to contaminate pea crops than is S. nigrum. Therefore, extra attention may be required where this species is present in process pea crops. The prevention of the flowering of both species, by the maintenance of the appropriate weed free period following pea sowing or crop emergence, was identified as potentially, the most useful means of reducing nightshade contamination in peas.
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Samson, Roger A. (Roger Anthony). "On-farm evaluation of cultivation, cover crops and chemical banding for crop and weed management in integrated farming systems." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55700.
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Fu, J. "Effects of different harvest start times on leafy vegetables (Lettuce, Pak Choi and Rocket) in a reaping and regrowth system." Lincoln University, 2008. http://hdl.handle.net/10182/670.
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Leafy vegetables, lettuce (Lactuca sativa L. cv. Green Oakleaf), pak choi (Brassica sinensis L. cv. Oriental Taisai) and rocket (Eruca sativa L.), were planted in an open field at Lincoln University on January 2005. Plants were harvested at 5 cm cutting height above the growing point with three different harvest start times, early start (ES), mid start (MS) and late start (LS) of harvest respectively. There were three harvests during the growing season with a 4-week interval between harvests. Generally, lettuce produced significantly higher total FW/plant (208 g) than pak choi or rocket (123 and 102 g total FW/plant, respectively). Lettuce also produced significantly higher total FW/plant than pak choi or rocket in each treatment. Lettuce produced significantly more total saleable leaf FW/plant in the ES, MS and LS treatment (137.5, 120.9 and 169.3 g FW/plant), compared with pak choi (52.9, 100 and 92 g FW/plant) or rocket (31.5, 92.2 and 56.4 g FW/plant). Pak choi produced higher total saleable leaf FW/plant than rocket in the ES and LS treatments, but a similar total saleable leaf FW/plant in the MS treatment. The best time to start harvesting was the LS treatment for lettuce, while pak choi and rocket produced better yields in the MS and LS treatments. Results for total DW/plant showed that different harvest start times did not affect the total DW/plant in lettuce. However, pak choi and rocket produced less total DW/plant in the ES treatment compared to the MS or LS treatments. This was due to a faster recovery by lettuce. In addition, lettuce produced significantly higher DW/plant during regrowth at the second and third harvests than pak choi or rocket, even though it was significantly lower at the first harvest. It is likely that after harvesting greater carbohydrate reserves and greater remaining leaf area produced greater regrowth potential in lettuce. These results suggest that lettuce has the most regrowth potential, while rocket has more than pak choi in this reaping and regrowth system. When plants were harvested at the same cutting level, lettuce had the most remaining leaf area of the three species. This remaining leaf area for lettuce could be another reason for faster recovery and more regrowth potential. More reserves and remaining leaf area may also be the reason for more regrowth potential in rocket compared to pak choi. Another important reason for the better performance of lettuce was that temperatures during the growing season were in the range of optimum temperatures (12-21 ºС), except for the regrowth between the second and third harvests in the LS. This relates to higher photosynthetic rates and in turn leads to faster recovery and regrwoth. Lettuce was the most suitable crop in the reaping and regrowth system in this experiment. However, rocket might also be appropriate for this system, particularly if the price is high enough to make it economically viable.
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Smith, Joshua Dwayne. "Impacts of Cover Crops on Carbon Dioxide and Nitrous Oxide Flux from a Row Crop Agricultural Field in Central Illinois." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1391.
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In the United States, there is renewed interest in incorporating cover crops into agricultural systems to provide a variety of potential benefits related to soil quality, water quality, and greenhouse gas emissions. This study focused on assessing whether cover crops influence N2O and CO2 emissions in a central Illinois agricultural research field over two years (2011-2013) of cover crop growing seasons. Three winter cover crop systems, annual ryegrass (Lolium multiflorum), cereal rye (Secale cereale), and a cereal rye (2011)/ hairy vetch (Vicia villosa) (2012) rotation were planted after fall 2011 and 2012 harvests. The field included a total of eight main plots, two of each treatment, and two no cover crop control plots. Soil carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were measured from the plots in a single corn (Zea mays) - soybean (Glycine max) system for two cover crop growing seasons. Fluxes of CO2 and CO2 were measured in March 2012, August 2012, and February 2013. The CO2 flux measurements were performed by using an infrared gas analyzer. The N2O fluxes were analyzed from samples collected at 0, 10, 20, 30 min intervals from the same closed dynamic chamber system. Both CO2 and N2O fluxes were computed from respective gas concentrations over time. Data were analyzed with a repeated measures mixed model procedure. N2O fluxes from the cereal rye/hairy vetch plots were greater than the no cover control and annual ryegrass plots, suggesting that cover crops may not decrease N2O fluxes immediately after being incorporated into a cropping system. In contrast, CO2 fluxes did not significantly differ among the treatments, but the cereal rye/hairy vetch plot sequestered ~100 kg C ha-1 of soil organic carbon (SOC). Overall, it was observed that some cover crop plots can have higher N2O fluxes than plots without cover crops, but cover crops have the long-term potential to sequester C in croplands demonstrating that their use should still be considered a sustainable agriculture practice.
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Sutherland, M. J. "The influence of vine vigour and canopy ideotype on fruit composition and aroma of Sauvignon Blanc." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1270.
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The influence of soil texture on canopy growth, vine yield, and fruit composition of Sauvignon blanc were assessed on a mature vineyard from the Rapaura area in Marlborough. The subject vines were mature Sauvignon blanc in a commercial vineyard trained to four cane VSP and planted with a north south orientation. Row and vine spacings were typical of the area at 3m x 1.8m. Four areas of different soil texture were identified using trunk circumference measurements, visual assessment of the surface soil and aerial photographs to identify changes in vine growth. Soil pits were excavated at a later date to determine root numbers and record the soil texture in the different areas. Two crop treatments were imposed on half of the plots at approximately 50% veraison: unthinned crop and 50% crop. A shading treatment was also imposed at 50% veraison where three sets of tagged shoots had bunches that were exposed to sunlight, bunches that had some natural shading from leaves or bunches that had paper bags fastened over each to provide a completely shaded environment. Vine vegetative vigour for each plot was assessed during the growing season using the Point Quadrat method and at pruning using bud counts and pruning weights. Thirty berry samples were collected from the 32 plots and analysed weekly for soluble solids and berry weight. Harvest of bunches from the tagged shoots occurred on two different dates with the first harvest picked when fruit from one soil and crop treatment had reached 21 °Brix. The second picking took place just before the commercial harvest, which coincided with last soil and crop treatment reaching 21 °Brix. Bunches from each tagged shoot were weighed, frozen and later analysed for soluble solids, pH, organic acids, and methoxypyrazines. Vines on very stony textured soils had small trunk circumferences with a high root density and yield to pruning weight ratio compared to those growing on deep silt soils. Vines on deep silt soils had more vigorous canopies with large shoots and a higher leaf layer number. The target soluble solids was reached first by the vines on the very stony plots despite the higher crop load with soil texture appearing to be a dominant factor by influencing the time of flowering. Cluster shading decreased soluble solids, consistent with other studies, whilst crop thinning resulted in an earlier harvest. This was contrary to popular opinion that crop thinning at veraison would have no impact on sugar accumulation. pH and organic acids were unaffected by shading or bunch thinning. Vines growing on deep silt soils had a significantly higher level of total acidity and malic acid than those on the stony soils. At harvest, methoxypyrazine levels were very low compared to previously reported figures for Marlborough, which may have been a result of sample preparation. IBMP was significantly higher on deep silt soils, however, with no impact from the shading or crop treatment. The findings are consistent with the hypothesis that IBMP synthesis may be increased by the number of leaves surrounding bunches (Roujou de Boubee, 2003). The results suggest that soil texture plays a dominant role in influencing Sauvignon blanc flavour and aroma and due consideration should be given to vineyard layout and site selection prior to new plantings taking place.
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Childerhouse, Emma. "The effect of a natural plant extract and synthetic plant growth regulators on growth, quality and endogenous hormones of Actinidia chinensis and Actinidia deliciosa fruit : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Horticultural Science at Massey University, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1052.
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Kiwifruit are of huge economic importance for New Zealand representing 29 percent of total horticultural exports. Fruit size is the biggest determinant of what consumers are willing to pay, and there is also a positive relationship between consumer preference for flavour and percentage dry matter. The two main cultivars exported from New Zealand are Actinidia chinensis ‘Hort 16A’ (gold kiwifruit) and A. deliciosa ‘Hayward’ (green kiwifruit). Under current commercial practice the only product allowed for use on kiwifruit to increase fruit size in New Zealand is Benefit®. Benefit® has been shown to induce different results when applied to A. chinensis and A. deliciosa, whereas synthetic plant growth regulators such as the cytokinin-like substance N-(2- chloro-4-pyridyl)-N’-phenylurea (CPPU) have been found to promote similar increases in fresh weight of fruit in both cultivars. Final fruit size is determined by both cell division and cell enlargement. It was been shown that fresh weight can be increased in both of the major Actinidia cultivars even though their physiology differs. Hormonal control of fruit size in relation to cell division and cell enlargement phases of fruit growth was studied in both A. chinensis and A. deliciosa. CPPU was applied to both cultivars in a growth response experiment where fruit were collected throughout the growing season. The objective of this experiment was to create growth curves, to compare and contrast the effect on A. chinensis and A. deliciosa, and to provide material for hormone analysis. Application of CPPU was found to significantly increase the fresh weight of both A. chinensis and A. deliciosa fruit (46.98 and 31.34 g increases respectively), and alter the ratio of inner and outer pericarps of A. chinensis fruit. CPPU and Benefit® were applied individually and together to both cultivars. It was found that only A. chinesis fruit were affected by the application of Benefit®; fresh weight was increased by 26.38 g, and percentage dry matter was significantly reduced. There was a statistically significant (p < 0.05) interaction between CPPU and Benefit® when applied to A. chinensis. 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) was applied to A. deliciosa on two application dates at three concentrations and was found to decrease fresh weight of fruit, but significantly increase percentage dry matter regardless of application date or concentration. Lastly CPPU and 1-naphthalene acetic acid (NAA) were applied to A. deliciosa at two application dates and in all combinations. Application date affected the response to both a low concentration of CPPU and NAA. A synergistic interaction was observed when CPPU was applied early plus NAA late (CPPU early (4.53 g increase) plus NAA late (13.29 g) < CPPU early plus NAA late (33.85 g). Finally endogenous hormone content was studied. Methods were developed and tested for the simultaneous analysis of both indole-3-acetic acid (IAA) and cytokinins. Freeze dried fruit were purified using Waters Sep-pak® cartridges and Oasis® columns then IAA was quantified by high pressure liquid chromatography. Preliminary results indicate a correlation between application of CPPU and endogenous IAA, high concentrations of IAA correlated well with periods of rapid fruit growth particularly for CPPU treated fruit.
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Tonmukayakul, Nop. "Water use efficiency of six dryland pastures in Canterbury." Lincoln University, 2009. http://hdl.handle.net/10182/1498.
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The annual and seasonal water use efficiency of six pasture combinations were calculated from the ‘MaxClover’ Grazing Experiment at Lincoln University. Pastures have been established for six years and are grazed by best management practices for each combination. Measurements for this study are from individual plots of four replicates of ryegrass (RG)/white clover (Wc), cocksfoot (CF)/Wc; CF/balansa (Bal) clover; CF/Caucasian (Cc) clover; CF/subterranean (Sub) clover or lucerne. Water extraction measurements showed soils for all dryland pastures had a similar plant available water content of 280±19.8 mm. Dry matter measurements of yield, botanical composition and herbage quality were assessed from 1 July 2008 until 30 June 2009. Lucerne had the highest annual yield of 14260 kg DM/ha/y followed by the CF/Sub at 9390 kg DM/ha/y and the other grass based pastures at ≤ 6900 kg DM/ha/y. All pastures used about 670±24.4 mm/y of water for growth. Lucerne had the highest annual water use efficiency (WUE) of 21 kg DM/ha/mm/y of water used (total yield/total WU). The WUE of CF/Sub was the second highest at 15 kg DM/ha/mm/y, and the lowest was CF/Wc at 9 kg DM/ha/mm/y. The CF/Sub pastures had the highest total legume content of all grass based pastures at 21% and as a consequence had the highest annual nitrogen yield of 190 kg N/ha. This was lower than the monoculture of lucerne (470 kg N/ha). Ryegrass/white clover had the highest total weed component in all pastures of 61%. For dryland farmers spring is vital for animal production when soil temperatures are rising and moisture levels are high. The water use efficiency at this time is important to maximize pasture production. In spring lucerne produced 8730 kg DM/ha, which was the highest dry matter yield of all pastures. The CF/Sub produced the second highest yield of 6100 kg/DM/ha. When calculated against thermal time, CF/Sub grew 5.9 kg DM/ºCd compared with lucerne at 4.9 kg DM/ºCd. The higher DM yield from lucerne was from an extra 400 ºCd of growth. The highest seasonal WUE of all pastures occurred in the spring growing period. Linear regressions forced through the origin, showed lucerne (1/7/08-4/12/08) had a WUE of 30 kg DM/ha/mm (R2=0.98). Of the grass based pastures, CF/Sub produced 18 kg DM/ha/mm (R2=0.98) from 1/7 to 10/11/08 from 270 mm of water used. The lowest spring WUE was 13.5 kg DM/ha/mm by CF/Bal pastures which was comparable to the 14.3±1.42 kg DM/ha/mm WUE of CF/Wc, CF/Cc and RG/Wc pastures. During the spring, CF/Sub clover had the highest spring legume component of the grass based pastures at 42% and produced 120 kg N/ha. This was lower than the 288 kg N/ha from the monoculture of lucerne. Sub clover was the most successful clover which persisted with the cocksfoot. Based on the results from this study dryland farmers should be encouraged to maximize the potential of lucerne on farm, use cocksfoot as the main grass species for persistence, rather than perennial ryegrass, and use subterranean clover as the main legume species in cocksfoot based pastures. By increasing the proportion of legume grown the water use efficiency of a pasture can be improved. When pastures are nitrogen deficient the use of inorganic nitrogen may also improve pasture yields particularly in spring.
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Acharyya, Abhijit. "Studies on the distribution, phenology and reproductive potential of some crop field weeds of Malda district,West Bengal,India." Thesis, University of North Bengal, 1998. http://hdl.handle.net/123456789/876.
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Nambuthiri, Susmitha Surendran. "Soil water and crop growth processes in a farmer's field." Lexington, Ky. : [University of Kentucky Libraries], 2010. http://hdl.handle.net/10225/1140.
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Thesis (Ph. D.)--University of Kentucky, 2010.<br>Title from document title page (viewed on May 12, 2010). Document formatted into pages; contains: xii, 310 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 298-309).
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Monks, D. P. "The vegetative and reproductive development of balansa clover." Lincoln University, 2009. http://hdl.handle.net/10182/1337.
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The vegetative and reproductive development of balansa clover (Trifolium michelianum Savi.) were quantified in relation to the environmental drivers of each phenophase in field and controlled environments. In a grazed experiment over 6 years, balansa clover sown with cocksfoot (Dactylis glomerata) contributed 1.6 t DM/ha/year, or ~20% of the total DM production. However, grazing management for increased seed production during flowering in the establishment year strongly influenced balansa clover regeneration. The earliest closed plot (September) averaged between 2.2 and 4.3 t DM/ha/year of balansa clover across all six years. In an incubator, balansa clover required 29°Cd for germination with an optimum temperature of 14°C and a maximum of 40°C. The base temperature for germination was 0°C. A field experiment determined that 38°Cd were required for emergence with an optimum soil temperature (Topt) of 8.5°C. The time from emergence until the first leaf appeared, the phyllochron and timing of axillary leaf appearance were compared with perennial ryegrass (Lolium perenne) and white clover (Trifolium repens L.). The rate of each was found to increase linearly with temperature. The balansa clover cultivar ‘Frontier’ required 97°Cd from sowing for the first leaf to appear, had a phyllochron of 47°Cd and secondary leaves appeared after 490°Cd. For each vegetative stage, the base temperature was 2.5°C. The timing of flower appearance depended on the quantity and direction of change of the photoperiod at emergence. A balansa clover plant, cv. ‘Bolta’, which emerged on 1 December into an increasing photoperiod of 15.6 hours flowered after 574°Cd (Tbase = 2.5°Cd) or 58 days after emergence. In contrast, if the plant emerged on 16 January into a similar but decreasing photoperiod it took 1503°Cd or 227 days to flower. This length of time became progressively shorter until remaining constant after the shortest day. In contrast, ‘Frontier’ took a constant 390 and 690 °Cd in increasing and decreasing photoperiods, respectively. The time which an individual inflorescence took from pollination until seeds were physiologically mature was 250 °Cd for both ‘Bolta’ and ‘Frontier’. The re-establishment of balansa clover each year relied on a large seed set (>1000 kg/ha) in the establishment year. The continued survival of balansa clover would then depend on a similar seeding event within a 4-5 year period to maintain the seed bank. Management considerations for balansa clover persistence and survival are discussed.
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Bates, Andrew John. "Effects of grazing management and pasture composition on the nitrogen dynamics of a dairy farm : a simulation analysis : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Lincoln University /." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1360.
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There is an extensive debate on the potential environmental impact of dairy farms and in particular the effect of dairy farms on the nitrogen cycle and the effect that this has on ecosystems. Within New Zealand and in particular in the South Island, the expansion of dairying and the adoption of new dairy systems has led to this becoming an increasingly important issue, locally through its effect on water quality and the environment and nationally and internationally through the production of green house gases. Increases in nitrogen usage at the expense of clover nitrogen fixation, irrigation, stocking rate and the introduction of dairy cows onto light free draining soils previously the preserve of arable or sheep farming has led to concern as to the effect intensive pastoral dairying may have on the nitrogen dynamics of the farm and the environment. This study is designed to assess how changes in grazing management in particular changes in pre-grazing and post-grazing residuals alter the clover/ryegrass balance on the farm and the effect that this has on the farm’s nitrogen dynamics. The effects of qualitative changes in grazing management on pasture composition are well established but little is known of the effect of quantitative changes in pasture management on composition, in particular the effect of grazing residuals. There are a number of detailed models of the physiological processes in the energy and nutrient cycling in plants, animals and the soil. There are a smaller number of whole farm models that through integration and simplification of component models attempt to represent the flux of nutrients though a dairy farm. None of these whole farm models is currently able to model the nitrogen flux through a dairy farm at a sufficient level of resolution to capture differences in pasture composition as these occur spatially, temporally and in response to grazing management. This project sought to better understand the nitrogen dynamics on a dairy farm by constructing and then linking component models – a pasture composition and growth model, a cow model, an excretal return model, a soil model and a water balance model – within a whole farm management schedule. The formal null hypothesis is that the mechanistic, mathematical model constructed for this PhD cannot capture and explain the full range of the changes in soil water content, soil nitrogen status, pasture production and composition and animal production, following the alteration in management of the dairy farm between 2002 and 2004. Individual component models were constructed by the author using the computer software package (Matlab) and validated against data extracted from the literature. The models were then converted into one simulation package using C-sharp as the source code language by Elizabeth Post, Senior Computer Scientist at Lincoln Ventures Ltd, Lincoln, New Zealand and the author. This model was then used to investigate the nitrogen dynamics of a dairy farm: the relationship with pasture composition and whether small changes in pasture residuals make a difference to pasture composition and nitrogen dynamics. Two different simulations were run based on the management practice of Lincoln University Dairy farm (LUDF) over two dairy seasons (2002-03 and 2003-04) and validated against the data recorded on this farm. In 2002-03, 50 cows were over wintered and 580 cows were subsequently milked on 200ha. Post grazing residuals where maintained at 1600-1750KgDM/ha. In 2003-04, 125 cows were overwintered and 635 cows were milked on 200ha with post grazing residuals maintained at 1400KgDm/ha. All models operate on a daily time step. Within the pasture model composition is described by 9 state variables describing different components of the pasture and pasture growth is modelled mechanistically from a calculation of component photosynthesis. A further 9 state variables describe the nitrogen composition of the pasture components. The soil model is a variable two layer, mechanistic representation, parametised for the shallow, stony soils of LUDF. Soil water status is an input for the pasture model while water uptake by the growing plants affects the soil water balance within the soil model. Animal intake and production are modelled mechanistically with model cows described in terms of their age, genetic merit, body weight, breed, pregnancy status, conception date and body condition score. Each cow type produces a different quantity of urinary and faecal excretion which varies with dry matter intake, milk yield and the sodium and potassium status of the pasture. Excretal nitrogen composition is predicted within a separate model which calculates daily nitrogen excretion in faeces, urine and milk. Excretions are deposited randomly over the grazed area and account is taken of overlapping excretions that are created on the same day and overlaps that occur with older excretal patches deposited in previous grazing rounds. Each excretal patch has its own associated pasture, water and soil model reflecting the differences in nitrogen status between patches. Grazing preference is expressed within the model between different classes of excretal patch and between excretal patches and the base pasture and between clover and grass. Supplementary silage is conserved and fed according to the management schedule of LUDF. Cows calve, become pregnant and are dried off within the model according to the relevant records from LUDF. Cows are deemed to arrive on the farm on the day of calving and to leave on the day that drying off is finished (a 5 day procedure within the model), except for those cows that are overwintering which remain on the farm. The soil model has multiple nitrogen/carbon pools and is dynamically linked to all the other models. External nitrogen losses from the system are modelled as volatilisation, leaching and denitrification, with pasture nitrogen uptake from the soil model and fixation by clover from the atmosphere. Both the individual component models and the final assembled composite model were successful in matching the available data in terms of pasture and animal production, pasture composition, soil water balance and nitrogen status and external losses. The model indicates that the low residual, high stocking rate farm returns more excreta to the soil. However, this is countered by a reduction in the amount of dead material returned to the paddock and this reduces the relative size of the pool of nitrogen in the dead organic matter. This produces a relative lack of substrate for the soil microbes which are thus unable to exploit all of the nitrogen in the available pool. Soil ammonium and nitrate pools are also increased from the increase in faecal and urinary return so precipitating an immobilising flux from these larger pools to the smaller pool of nitrogen available to the soil microbes. However, the relative inability of the soil bacteria to fully exploit this means that the production of soil organic live matter and the resulting mineralising flux from the dead organic matter pool through the available pool to the ammonium and nitrate pools is reduced. The larger ammonium and nitrate pools will also be associated with increased external losses from the system as denitrification, leaching and volatilisation are increased. The increase in the clover percentage within the sward in 2003-04 led to greater nitrogen fixation and the model suggests that some of the extra nitrogen is effectively captured by the animals in increased production. However, the reduction in the return of dead matter coupled with an increase in excretal return and the consequent increase in the mineral nitrogen pools within the soil lead to greater losses of nitrogen from the soil.
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Craft, Kortney E. "Economic Impacts of Drought on Kentucky Corn, Hay, and Soybeans." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1066.
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Understanding climatic impacts is important if we are to comprehend the relationship between climate and society. Weather phenomena can have environmental, economical, and social impacts. Drought is the natural hazard that affects people the most. It is also the most complex and least understood. There is no one universally accepted definition for drought which makes its examination difficult. Droughts’ duration is also difficult to determine because it has no clearly defined onset and end. Also, drought varies both geographically and temporally making uniform drought monitoring difficult. Since drought is difficult to monitor and access, drought impacts are often poorly documented. The purpose of this research was to quantify (in dollars) the impacts of drought on Kentucky’s agriculture. Drought has been recorded historically in Kentucky since the late 1800s. According to the Kentucky Climate Center, the most significant drought years occurred in 1930-31, 1940-42, and 1952-55. Analyses of these years are included as well as the most recent significant drought years in 1987-88, 1999- 2000 and 2007. Four of Kentucky’s important commodities, including corn, soybeans, hay, and beef cattle, were examined during the significant drought years. The total state revenue for these commodities was analyzed during severe drought years vs. non-severe drought years. The result of this research identified how much of a deficit severe drought causes on Kentucky revenue for each of these commodities. This research is important to the general public as well as planners and policy makers. Proper documentation of drought impacts will help identify drought vulnerabilities and result in better risk management and mitigation. Key Words: Drought, Agriculture, Impact Assessment
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Kang, Sideth. "Effect of irrigation on growth and nitrogen accumulation of Kabuli chickpea (Cicer arietinum L.) and narrow-leafed lupin (Lupinus angustifolius L.)." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1126.
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A field experiment was conducted to examine the responses in growth, total dry matter (TDM), seed yield and nitrogen (N) accumulation of Kabuli chickpea cv. Principe and narrow-leafed lupin cv. Fest to different irrigation levels and N fertilizer on a Templeton silt loam soil at Lincoln University, Canterbury, New Zealand in 2007/08. The irrigation and fertilizer treatments were double full irrigation, full irrigation, half irrigation and nil irrigation and a control, full irrigation plus 150 kg N ha⁻¹. There was a 51 % increase in the weighed mean absolute growth rate (WMAGR) by full irrigation over no irrigation. The maximum growth rates (MGR) followed a similar response. The growth rates were not significantly decreased by double irrigation. Further, N fertilizer did not significantly improve crop growth rates. With full irrigation MGRs were 27.6 and 34.1 g m⁻² day⁻¹ for Kabuli chickpea and narrow-leafed lupin, respectively. Seed yields of fully-irrigated crops were trebled over the nil irrigation treatment. With full irrigation, seed yield of chickpea was 326 and that of lupin was 581 g m⁻². Seed yield of the two legumes was reduced by 45 % with double irrigation compared with full irrigation. Nitrogen fertilizer did not increase seed yields in either legume. Increased seed yield with full irrigation was related to increased DM, and crop growth rates, seeds pod⁻¹ and seeds m⁻². Crop harvest index (CHI) was significantly (P < 0.05) increased by irrigation and was related to seed yield only in narrow-leafed lupin. With full irrigation, the crops intercepted more than 95 % of incoming incident radiation at leaf area indices (LAIs), 2.9 and 3 or greater in Kabuli chickpea and narrow-leafed lupin, respectively. In contrast, without irrigation the two legumes achieved a maximum fraction of radiation intercepted of less than 90 %. With full irrigation, total intercepted photosynthetically active radiation (PAR) was increased by 28 % and 33 % over no irrigation for Kabuli chickpea and narrow-leafed lupin, respectively. Fully-irrigated Kabuli chickpea intercepted a total amount of PAR of 807 MJ m⁻² and fully-irrigated narrow-leafed lupin intercepted 1,042 MJ m⁻². Accumulated DM was strongly related to accumulated intercepted PAR (R² ≥ 0.96**). The final RUE was significantly (P < 0.001) increased by irrigation. With full irrigation the final RUE of Kabuli chickpea was 1.49 g DM MJ⁻¹ PAR and that of narrow-leafed lupin was 2.17 g DM MJ⁻¹ PAR. Total N accumulation of Kabuli chickpea was not significantly affected by irrigation level. Kabuli chickpea total N was increased by 90 % by N fertilizer compared to fully-irrigated Kabuli chickpea which produced 17.7 g N m⁻². In contrast, total N accumulated in narrow-leafed lupin was not increased by N fertilizer but was decreased by 75 % with no irrigation and by 25 % with double irrigation (water logging) compared to full irrigation with a total N of 45.9 g m⁻². Total N was highly significantly related to TDM (R² = 0.78** for Kabuli chickpea and R² = 0.99** for narrow-leafed lupin). Nitrogen accumulation efficiency (NAE) of narrow-leafed lupin was not affected by irrigation or by N fertilizer. However, the NAE of Kabuli chickpea ranged from 0.013 (full irrigation) to 0.020 (no irrigation) and 0.017 g N g⁻¹ DM (full irrigation with N fertilizer). The N harvest index (NHI) was not affected by irrigation, N fertilizer or legume species. The NHI of Kabuli chickpea was 0.50 and that of narrow-leafed lupin was 0.51. The NHI was significantly (r ≥ 0.95 **) related to CHI.
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Kean, J. M. "Metapopulation theory in practice." Lincoln University, 1999. http://hdl.handle.net/10182/1372.
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A metapopulation is defined as a set of potential local populations among which dispersal may occur. Metapopulation theory has grown rapidly in recent years, but much has focused on the mathematical properties of metapopulations rather than their relevance to real systems. Indeed, barring some notable exceptions, metapopulation theory remains largely untested in the field. This thesis investigates the importance of metapopulation structure in the ‘real world’, firstly by building additional realism into metapopulation models, and secondly through a 3-year field study of a real metapopulation system. The modelling analyses include discrete-and continuous-time models, and cover single species, host-parasitoid, and disease-host systems, with and without stochasticity. In all cases, metapopulation structure enhanced species persistence in time, and often allowed long-term continuance of otherwise non-persistent interactions. Spatial heterogeneity and patterning was evident whenever local populations were stochastic or deterministically unstable in isolation. In metapopulations, the latter case often gave rise to self-organising spatial patterns. These were composed of spiral wave fronts (or ‘arcs of infection’ in disease models) of different sizes, and were related to the stability characteristics of local populations as well as the dispersal rates. There was no evidence for self-organising spatial patterns in the host-parasitoid system studied in the field (the weevil Sitona discoideus and its braconid parasitoid Microctonus aethiopoides), and a new model for the interaction suggested that this is probably due to the strong host density-dependence and stabilising parasitism acting on local populations. Dispersal may be important because of very high mortality in dispersing weevils, which may be related to the scarcity of their host plant in the landscape. If this is the case, the model suggested that local weevil density may be sensitive to the area of crop grown. Stochastic models showed that species in suitably large metapopulations may persist for very long times at relatively low overall density and with very low incidence of density-dependence. This suggests that metapopulation processes may explain a general inability to detect density-dependence in many real populations, and may also play an important part in the persistence of rare species. For host-parasitoid metapopulation models, persistence often depended on the way in which they were initialised. Initial conditions corresponding to a biological control release were the least likely to persist, and the maximum host suppression observed in this case was 84%, as compared with 60% for the corresponding non-spatial models and >90% often observed in the field. Metapopulation structure also allowed persistence of ‘boom-bust’ disease models, although the dynamics of these were particularly dependent on assumptions about what happens to disease classes at very low densities. Models assuming infinitely divisible units of density, models incorporating a non-zero extinction threshold, and individual-based models all gave differing results in terms of disease persistence and rate of spatial spread. Fitting models to overall metapopulation dynamics often gave misleading results in terms of underlying local dynamics, emphasising the need to sample real populations at an appropriate scale when seeking to understand their behaviour.
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Villarreal, Manzo Luis Alberto. "Water Conservation in Biofuels Development: Greenhouse and Field Crop Production with Biochar." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195060.
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Biochar incorporation in soils has the potential to remove carbon from the atmosphere and to improve soil quality. This research focused on evaluation of the benefit of biochar incorporation in an Arizona soil. Different concentrations of biochar (charcoal from mesquite biomass-derived black carbon) were added to soil in greenhouse experiments. Seven common or potential Southern Arizona crops (alfalfa, wheat, cotton, grain and sweet sorghum, barley and switch grass) were evaluated in the greenhouse experiment. In this experiment; increased biochar concentration treatments produced greater height and biomass production in alfalfa. Sorghum biomass production also increased with biochar concentration. There were no significant differences in biomass production in wheat and barley with increased biochar concentration. Switch grass biomass production had a significant negative correlation with increased biochar concentration. Sweet sorghum biomass production was evaluated in a field experiment conducted at the University of Arizona Red Rock Agricultural Center. A relatively small amount of biochar was incorporated in the top 20 cm of soil in one treatment and soil only was the other treatment: there were no significant differences in yield.Water characteristic curves and bulk densities were measured for biochar/soil mixes. The FASE model was used to simulate evapotranspiration and crop yield for the field sorghum experiment and for several crops grown in the Valsequillo Irrigation District, Puebla, Mexico with measured soil parameters. The model predicted no significant increase in sorghum yield for the level of biochar incorporated in the soil. An increase in yield was predicted for Valsequillo crops.
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Leathwick, D. M. "Applied ecology of the Tasmanian lacewing Micromus tasmaniae Walker (Neuroptera : Hemerodiidae)." Lincoln College, University of Canterbury, 1989. http://hdl.handle.net/10182/1044.
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The Tasmanian lacewing (Micromus tasmaniae Walker) is one of the most common aphid predators occurring in lucerne crops in New Zealand. A comparison of sampling techniques, and the output from a simulation model, suggest that the abundance of this lacewing may have been significantly underestimated in the past. Although the occurrence of aphid predators was erratic M. tasmaniae occurred more often and in far greater numbers (up to 100 m⁻²) than any other predator species. A simulation model for lacewing development in the field indicated that the large adult populations which occurred could be accounted for on the basis of reproductive recruitment. Independent evidence that immigration was not involved in the occurrence of these large populations was gathered using directional flight traps around the field perimeter. The major factors influencing lacewing population dynamics were the availability of aphid prey and, in the autumn, parasitism. Otherwise, survival of all life-histoty stages was high with no evidence of egg or larval cannibalism. Several instances of high lacewing mortality were identified by the model and the lack of any obvious cause for these highlights inadequacies in the understanding of lacewing bionomics. The model, which used a linear relationship (day-degrees) between development and temperature, was incapable of accurately predicting lacewing emergence under field temperatures which fluctuated outside the linear region of the development rate curve. Temperature thresholds and thermal requirements estimated under fluctuating temperatures similar to those in the field produced almost identical model output to those estimated under constant temperatures in the laboratory. Prey species was capable of influencing the rate of lacewing development. M. tasmaniae has the attributes necessary to produce large populations in the short time available between lucerne harvests. The asymptote of the functional response curve is low but the efficiency at converting aphids to eggs is high. Therefore, the lacewing is able to attain maximun reproductive output at low prey densities. A low temperature threshold for development (4-5° C), rapid development and short preoviposition period results in a short generation time (49 days at 15° C). Long adult life, high fecundity and the absence of any form of estivation or diapause, results in complete overlap of generations and multiple generations per year. M. tasmaniae's role as an aphid predator is restricted by its low appetite for prey and by the lucerne management regime currently practiced in New Zealand. Because it consumes relatively few aphids per day the lacewing's ability to destroy large aphid populations is limited. However, this may be offset by its ability to attack aphids early in the aphid population growth phase, and by the large numbers of lacewings which may occur. Under the present lucerne management schemes the large lacewing populations which do occur are forced out of the fields, or die, following harvest. A number of management options for increasing the lacewings impact as an aphid predator are briefly discussed.
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Bourguignon, Emmanuel. "Ecology and diversity of indigenous Trichoderma species in vegetable cropping systems." Lincoln University, 2008. http://hdl.handle.net/10182/641.
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The overall aim of this research was to improve the understanding of the ecology and diversity of Trichoderma species within the soil and rhizosphere of onion (Allium cepa L.) and potato (Solanum tuberosum L.) under intensive management in New Zealand. The indigenous Trichoderma population was measured in a field trial at Pukekohe over a three year period under six different crop rotation treatments. The treatments included two continuous onion and potato rotations (intensive), two onion/potato mixed rotation (conventional), and two green manure rotations (sustainable). Results showed that Trichoderma populations were stable in both the rhizosphere and bulk soil (1.5 x 10² to 8.5 x 10³ CFU g⁻¹ ODS). The planting and incorporation of an oat (Avena sativa L.) green manure in the sustainable rotations positively increased Trichoderma colony forming unit (CFU) numbers in the rhizosphere soil from 3.4 x 10² to 2.5 x 10³ g⁻¹ ODS. A Trichoderma species identification method was developed based on colony morphology. Representative isolates were verified using restriction fragment length polymorphism (RFLP) and DNA sequencing. The method allowed for rapid and reliable identification of isolated Trichoderma species. Five species were identified in the Pukekohe soil: T. asperellum, T. atroviride, T. hamatum, T. harzianum and T. koningii. Results showed identical species diversity between the rhizosphere, rhizoplane and bulk soil. The species did not strongly compete between each other for the rhizosphere ecological niche and differences in species proportions seemed to be caused by environmental factors rather than the rotation treatments. The incorporation of oat green manure in pots did not significantly promote the indigenous Trichoderma population size and diversity in the rhizosphere of onion plants up to 4 months old. The identified species were the same as in the field trial. The incorporation of onion scale residues was shown to result in low Trichoderma and high Penicillium CFU numbers and a reduction in plant size. Additionally, the presence of high levels (6.0 x 10⁵ CFU g⁻¹ ODS) of Penicillium CFU was negatively correlated with the presence of Trichoderma CFU. The effect of oat incorporation on Trichoderma saprophytic growth was also investigated in a soil sandwich assay and revealed no significant differences. A series of experiments indicated that onion extract obtained from dry onion scale residues had no antifungal activity against either Trichoderma or Penicillium and instead tended to promote their hyphal growth and sporulation. It also showed that competition between Penicillium and Trichoderma isolates was limited despite the ability of Penicillium to produce a wide range of inhibitory substances. Four indigenous Trichoderma species (T. atroviride, T. hamatum, T. harzianum and T. koningii) were shown to be rhizosphere competent in a split tube experiment over a 6 week period. The results of this experiment revealed that, the Trichoderma species clearly displayed differences in their ability to colonise the rhizosphere of young onion seedlings. Species such as T. koningii had the greatest rhizosphere colonising ability regardless of soil depth while T. harzianum displayed the weakest ability. Results also indicated that when inoculated as a mixture the four species competed with one another to colonise the rhizosphere. Overall, this research indicated that the studied crop rotation treatments and the use of oat as a green manure did not strongly promote indigenous Trichoderma populations. Species diversity was constant throughout the research with T. hamatum and T. koningii being the most frequently isolated species.
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Patterson, R. G. "A study of the soils and agronomy of a high country catchment." Lincoln University, 1993. http://hdl.handle.net/10182/1315.
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This study was undertaken to research the principles and practices behind increased pasture productivity on Longslip Station, Omarama. A range of landscape - soil - climate - plant systems were identified, then analysed and the legume responses measured. By isolating cause and effect and appreciating the driving variables of each system, lessons learnt could be reliably and objectively transferred to the rest of the farm. Extrapolation to the balance of the property (15,150 ha) permitted immediate large-scale development and engendered confidence to lending institutions, Lands Department, catchment authorities and ourselves. Soil (land) cannot be well managed and conserved unless it is mapped reliably and its characteristics measured and interpreted by skilled observers (Cutler, 1977). Soil resource surveys, and their interpretation, are an essential ingredient of rational resource evaluation and planning. This thesis is a figurative and comparative survey and study of the soil catenary bodies, resident vegetation, legume establishment and pasture production characteristics of a 400 hectare catchment, in relation to, and as influenced by soil landscape unit, slope component, altitude, aspect and time. The inherent diversity in landform, soil properties and vegetation communities in a single catchment in the high country has not previously been fully studied or appreciated. This has lead to blanket recommendations for fertilizer, seed and management regimes both within and between properties and even regions. This study reports on the diversity of, yet predictable change in soil properties with slope position (upper, middle and lower) aspect and altitude in terms of both soil physical properties e.g. soil depth and water holding capacity and soil chemical properties such as pH, BS%, %P, %S, %N and %C. The composition of the resident vegetation and its differential response to oversowing and topdressing and subsequent change through time is reported and discussed. Finally an epilogue gives an insight into the problems and frustrations of farming practices in the high country from a motivation and personal perspective and political point of view that it is essential to come to terms with.
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Wadsworth, A. C. "Control of spikelet survival in spring barley cv. Maris Mink." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379532.
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Whelan, Brett Michael. "Reconciling continuous soil variation and crop yield : a study of some implications of within-field variability for site-specific crop management." Thesis, University of Sydney, 1998. https://hdl.handle.net/2123/27516.
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Within-field variability in cropping system attributes is often obvious but difficult to accurately and efficiently quantity. The magnitude of the variation also changes with attribute, location and time. Importantly, variability at this scale of the soil/crop system may give rise to economic, environmental and societal problems on cropping enterprises under traditional 'uniform' management. In general, the problems arise from a decision to use 'mean-of-field' information to guide the amelioration of an area which may result in zones being under-or over-treated. Gathering data on, and extracting useful management information from, within-field variability is the goal of Precision Agriculture.
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Chen, Changping 1958. "Production variability for major Arizona field crops." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/291617.
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Previous variability studies in both U.S. and worldwide agriculture have indicated that crop production has been accompanied by increasing variation. In this research, four different variability indexes were estimated in order to evaluate the production variability associated with the major Arizona field crops. Results show that major Arizona field crops, which are all irrigated, did not have a uniform production variability over the last 24 years and the variability of these crops did not generally increase between the periods of 1967-1978 and 1979-1990. Although biological factors (e.g. pests, weather) influenced variability, the variation of crop production measures over time also was related to market factors (e.g. prices), government farm programs, producers' crop management experience, and the geographical area selected for the analysis. Crops covered by government farm programs usually varied more in harvested acreage and fluctuated less in yield per acre than vegetable crops.