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Includes bibliographical references (leaves 11-1-11-26). / xv, 222 leaves : ill. (some col.) : 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Agronomy and Farming Systems, 2001

"June 2001." Includes bibliographical references (leaves 217-248). The effects of a sustained period of moderately high temperature on physiological and biochemical aspects of grain development were investigated in wheat cultivars grown under controlled environment conditions. The effect of variation in plant nutrition on the responses of cultivars to high temperature was also studied.

"June 2001." / Includes bibliographical references (leaves 217-248). / vi, 248 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The effects of a sustained period of moderately high temperature on physiological and biochemical aspects of grain development were investigated in wheat cultivars grown under controlled environment conditions. The effect of variation in plant nutrition on the responses of cultivars to high temperature was also studied. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 2001?

Wheat consumption has become more widespread and is increasing in South Africa especially in the urban areas. The wheat industry contributes four billion rands to the gross value of agriculture and is a source of employment to approximately 28 000 people. Wheat yield forecasting is crucial in planning for imports and exports depending on the expected yields and wheat health monitoring is important in minimizing crop losses. However, current crop surveying techniques used in South Africa rely on manual field surveys and aerial surveys, which are costly and not timely (after harvest). This research focuses on wheat health monitoring and wheat yield prediction using remote sensing, which is a cost effective, reliable and time saving alternative to manual surveys. Hence, the research objectives were: (i) to identify remotely sensed spectral indices that comprehensively describe wheat health status. (ii) Develop an Normalized Difference Vegetation Index (NDVI) based wheat yield forecasting model and (iii) to evaluate the impact of selected agrometeorological parameters on the NDVI based forecasting model. Landsat 8 images were used for determining spectral indices suitable for wheat health monitoring by relating the spectral indices to the land surface temperature. Results show that the Normalized Difference Water Index (R2 between 0.65 and 0.89) and NDVI (R2 between 0.36 and 0.62) were the most suitable indices for wheat health status monitoring. Whereas, the Normalized Difference Moisture Index (R2 between 0.53 and 0.79) and the Green Normalized Difference Vegetation Index (R2 between 0.28 and 0.41) were found to be less suitable for wheat health monitoring. Moderate Resolution Spectroradiometer (MODIS) derived NDVI for fourteen years was used to build and test a wheat yield forecasting model. The model was significant with an R2 value of 0.73, a p-value of 0.00161 and an RMSE of 0.41 tons ha-1. The study established that the period 30 days before harvest during the anthesis growth stage, is the best period to use the linear regression model for wheat yield forecasting. Satellite derived agrometeorological parameters such as: soil moisture, evapotranspiration and land surface temperature were added to the NDVI based model to form a multi-linear regression model. The addition of these parameters to the NDVI model improved it from an R2 of 0.73 to an R2 of 0.82. Through the use of a correlation matrix, the NDVI (r=0.88) and evapotranspiration (r=0.58) were highly correlated to wheat yield as compared to soil moisture (r=0.27) and land surface temperature (r=-0.02). This research provided evidence that remote sensing can be used at acceptable levels of accuracy for wheat monitoring and wheat yield predictions compared to manual field surveys which are costly and time consuming. / Dissertation (MSc)--University of Pretoria, 2017. / Agricultural Research Council / National Research Foundation / Spatial Business IQ / GeoTerra Images / University of Pretoria / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

<p>U regionu severnog Banata se uglavnom primenjuje<br />konvencionalni način obrade zemlji&scaron;ta, zasnovan na obradi<br />plugom, kao primarna obrada koji je spor, skup i zahteva veliki<br />utro&scaron;ak rada i goriva. Takva obrada je sa ekolo&scaron;kog stanovi&scaron;ta<br />nepovoljna i neodrživa. U poslednjih trideset godina, naučna<br />saznanja o obradi zemlji&scaron;ta u svetu se menjaju u pravcu<br />pojednostavljenja obrade i smanjenja prohoda. Savremeni sistemi<br />obrade su u Srbiji nedovoljno istraženi, a cilj ovoga rada je da se<br />optimizuje obrada zemlji&scaron;ta za date uslove. Za potrebe istraživanja<br />je postavljen ogled u trajanju od tri godine (2011/2012, 2012/2013<br />i 2013/2014), pri čemu je uzgajan kukuruz, p&scaron;enica i kukuruz, tim<br />redosledom. Svaka kultura je uzgajana u tri sistema obrade:<br />konvencionalna obrada bazirana na plugu, direktna setva i<br />konzervacijska obrada bazirana na razrivaču, pri čemu je Ďubrenje<br />bilo uniformno. U radu je analiziran uticaj različitih načina obrade<br />na specifični otpor zemlji&scaron;ta, fizičke i hemijske osobine zemlji&scaron;ta i<br />živi svet u zemlji&scaron;tu (brojnost glista). Uspe&scaron;nost poljoprivredne<br />proizvodnje se ogleda kroz ostvareni prinos i utro&scaron;ena sredstva,<br />zbog čega je utvrĎen najprinosniji i ekolo&scaron;ki najprihvatljiviji način<br />obrade zemlji&scaron;ta. Pored navedenog, analiziran je uticaj različitih<br />rasprskivača pri tretiranju useva pesticidima na prisustvo ostataka<br />pecticida u zemlji&scaron;tu</p> / <p>Conventional tillage is the most frequently applied tillage method in the<br />area of northern Banat. It is based on ploughing as the primary tillage<br />operation, which is slow, costly, and requires large expenditure of labour<br />and fuel. Such treatment can be ecologically unfavourable, and it is not<br />sustainable. In the last thirty years, global knowledge about soil tillage<br />has been changing towards simplification and reduced soil tillage.<br />Contemporary tillage systems in Serbia are not studied thoroughly<br />enough, but the goal of this work was to optimize soil tillage for the given<br />conditions. The trial was set up during the period of three years<br />(2011/2012, 2012/2013, and 2013/2014), in which corn, wheat, and corn<br />were cultivated, respectively. Each crop was grown using three tillage<br />systems - conventional tillage based on ploughing, direct seeding, and<br />conservation tillage based on tine cultivator, whereas fertilization was<br />uniform in all the systems. This dissertation analyzes the impact of<br />different tillage on soil resistance, physical and chemical properties of<br />soil, as well as biota in the soil (number of earthworms). Success of<br />agricultural production is reflected in yield and expenses, therefore this<br />dissertation determins the highest yielding and most environmentally<br />friendly system of tillage. In addition, it analyzes the impact of using<br />different kinds of nozzles in treating crops on the pesticide residues in the<br />soil.</p>

In order to reduce the vulnerability of wheat production to drought, a calibrated and validated CERES Wheat crop simulation model was used to predict wheat yields on major soil textural groups using historical weather data at Swift Current, Saskatoon and Melfort. Yields were predicted using a run-out technique which involved the use of actual weather data to the prediction date and historical weather data from 1960 to 1990 for the remainder of the growing season. Yield predictions were made at five Julian dates during the crop calendar and these dates coincided with crop emergence, terminal spikelet initiation, end of the vegetative growth, heading and start of grain filling. Three sample years were used as case studies to test the applicability of the run-out method in making yield predictions. Sample base years were those with the lowest, medium and highest yields between 1960 and 1990 and these were selected from ranked yield values using quartiles. Test years were termed base years and weather files that were joined with the test years were run-out years. Each base year had 30 run-out years (1960-1990) and the mean of each run-out year was compared with the observed yield at the end of the season. Run-out yields for each base year were summarised as simple probability distributions so that yields exceeding certain values could be selected. Run-out yields at five prediction dates were found to be in close agreement with observed yields at the end of the growing season. To account for the variability in yields that can be found between places within the same climatic zone, simulated yields were re-classified by soil type and water stress level. These modifiers (soil type and water stress level) showed that chances of getting high yields diminish from Melfort to Swift Current at all prediction points due to the high variability of yield factors. Yield predictions that were made as above suggested that if historical weather records are combined with available weather data during the growing season, a good indication of yields can be obtained ahead of the harvest time and this could allow producers and those in the agri-business to decide on alternative actions of minimizing losses when prospects of getting a good yield are poor.

The simple effects of nitrogen rates, fungicide application, and varietal responses on wheat yield and quality have been studied individually, but interactions among the inputs are less well understood. Traditionally, increased nitrogen rates have led to higher risk of lodging and disease severity (Roth and Marshall, 1987), but it has been found that fungicides can be used to delay the onset of disease (Gooding et al. 1999). Similarly, yield responses to application of a fungicide may be affected by available nitrogen (Olesen et al., 2003). Wheat quality parameters such as protein, test weight, and alveograph parameters may also be affected by different management systems. Recent Ontario research shows interactions between fungicide and wheat varieties, even in the absence of disease, but the relationships are poorly understood. Current field crop recommendations would be improved by knowledge of interactions between inputs in more intensive management systems. Field experiments were established on nine farm fields in southwestern Ontario to investigate possible interactions among nitrogen rates, fungicides, and varieties. Eight fungicide timing combinations were applied as splits on three N rate blocks (100, 135, and 170 kg ha-1), applied across variety strips (between three and seven) in a split-strip-plot design with three replicates. Measurements included leaf disease severity, fusarium head blight incidence and severity and mycotoxin concentrations, grain yield and yield components, protein, test weight, and alveograph parameters. An economic analysis was performed on the combinations of treatment variables toward the development of more comprehensive recommendations. Interaction between N application rate and fungicide application resulted in greater yield gains with increased N when fungicides were used. Grain protein concentration increased at higher N application rates. Revenue net of the variable costs examined was not significantly affected by N rate alone, while effect of fungicide application varied with site. / Agricultural Adaptation Council, Grain Farmers of Ontario

The effects of soil nutrient status on the performance of four South African wheat genotypes were investigated in a long-term fertilization experiment. The objective was to quantify the effects of soil fertility on yield, yield components, grain nitrogen content, grain protein yield, grain protein content, flour yield and bread-making quality. The relative contribution of main stems and tillers, as well as the contribution of first, second and third kernels in the spikelets to grain yield and grain protein content were determined. The interactive effects between photoperiod, temperature and vernalization on grain yield, yield components and grain protein content were also quantified. Increasing soil fertility increased grain yield and most components of yield, grain nitrogen content, grain protein yield, aboveground biomass and harvest index, but depressed mean kernel mass. Significant interactions between cultivar and soil fertility were observed for grain yield, grain number, kernel mass, protein yield, biomass and harvest index, indicating differences in cultivar ability to produce yield and quality. Within a cultivar, the main stem, first tiller and second tiller did not differ in mean grain protein content, indicating that late-maturing tillers do not affect the grain protein content of wheat. Grain protein content, flour yield, loaf volume, water absorption and mixograph peak mixing time varied with soil fertility. The interaction between cultivar and soil fertility was significant for the above mentioned parameters with the exception of mixograph peak mixing time, indicating wheat genotypes differences in bread-making quality potential. The potential ability of wheat cultivar Kariega to produce higher grain yield, protein yield and loaf volume in the K and P limiting soil fertility situations deserve further investigation. In a growth chamber study, the low temperature regimes and long photoperiod conditions resulted in the highest grain yield, number of grains, largest mean kernel size and highest grain protein content. / Dissertation (PhD)--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

Made available in DSpace on 2017-07-25T19:30:46Z (GMT). No. of bitstreams: 1 Daniel Potma.pdf: 2269780 bytes, checksum: 5e498b4886f52a509f48ad0c44a512b3 (MD5) Previous issue date: 2014-07-23 / The total organic C (TOC) of the soil influences their chemical, physical and biological properties, therefore, it's important for the maintenance of soil fertility mainly of tropical soils. But, while the benefits of TOC accumulation on soil quality are well known, there is still little information about its effects on crop yields. The aims of this work were to map the compartments of the TOC on a farm managed for 30 years in no-till system, determine which soil variables that influence the spatial variation of TOC and analyze the relationships between the compartments of TOC and crop yields of soybean, corn and wheat. Deformed samples were collected in all soil classes and all landscape positions in the farm. Were analyzed the TOC, the permanganate oxidized C (POX-C) and the hot water extracted C (HWE-C) and were generated maps with the spatial variation of these variables. The effects of soil properties on the accumulation of TOC and the effect of TOC compartments on yields of soybean, corn and wheat were accessed through regressions and principal component analysis. Aiming to access the contribution of TOC to the crop yields, multiple regressions with the soil variables and yields were adjusted. The higher clay content and the largest biomass apport in Oxisols and the formation of an anaerobic environment in Inceptisols were the main factors that explained the highest contents of TOC observed in the upper thirds of the Oxisols and lower thirds of the Inceptisols. Yields of wheat and soybean showed positive correlation with TOC and total N (TN) and corn yield was positively correlated with HWE-C. The TN and TOC were the variables that contributed most to explain the variations in the wheat yield. / O C orgânico total (COT) do solo exerce influência sobre suas propriedades químicas, físicas e biológicas, sendo assim, importante para a manutenção da fertilidade principalmente de solos tropicais. Porém, embora os benefícios do acúmulo de COT sobre a qualidade do solo sejam bem conhecidos, ainda são escassas informações referentes aos seus efeitos sobre a produtividade de culturas. Os objetivos deste estudo foram mapear os compartimentos de COT em uma fazenda manejada há 30 anos no sistema plantio direto, verificar quais são as variáveis do solo que interferem na variação espacial do COT e analisar as relações entre os compartimentos do COT e a produtividade das culturas da soja, milho e trigo. Foram coletadas amostras deformadas em todas as principais classes de solos da fazenda em todas as posições da paisagem. Foram analisados o COT, o C oxidado por permanganato (C-OXP) e o C extraído por água quente (C-EAQ) e gerados mapas com a variação espacial destas variáveis. Os efeitos dos atributos do solo sobre o acúmulo de COT e dos compartimentos de COT sobre as produtividades da soja, milho e trigo foram acessados através de regressões e análises de componentes principais. Visando acessar a contribuição do COT para as produtividades das culturas foram ajustadas regressões múltiplas com as variáveis do solo e as produtividades. O maior conteúdo de argila e a maior adição de fitomassa nos Latossolos e a formação de um ambiente anaeróbico nos Cambissolos foram os principais fatores que explicaram os maiores conteúdos de COT observados nos terços superior dos Latossolos e inferior dos Cambissolos. As produtividades de trigo e soja apresentaram correlação positiva com o COT e o N total (NT) e a produtividade de milho apresentou correlação positiva com o C-EAQ. As variáveis NT e COT foram as que mais contribuíram para explicar a variação da produtividade de trigo.