A operação de adubação responde por parte significativa dos custos de produção agrícola. Melhorar a qualidade dessa operação acarreta benefícios econômicos e ambientais. O processo de adubação normalmente é realizado a uma taxa média, representativa de uma área, no entanto, propriedades químicas do solo podem variar consideravelmente dentro dessa área. Desse modo, alguns locais poderão receber fertilizantes e/ou corretivos em excesso, enquanto outros poderão receber quantidades insuficientes. A alternativa à taxa média é a realizar a aplicação à taxa variada, que se caracteriza por aplicar os insumos de acordo com as necessidades específicas dentro da área. Para que essa aplicação aconteça, mecanismos dosadores controlam a aplicação. O objetivo deste estudo é avaliar os mecanismos dosadores de uma carreta adubadora de arrasto, comportas e esteiras, atendem as prescrições de doses previstas no mapa de recomendação de adubação. Para avaliar a uniformidade da operação utilizou-se o controle estatístico do processo. De acordo com os resultados obtidos pode-se afirmar que os mecanismos dosadores não atenderam a condição de realizar a aplicação à taxa variável de maneira uniforme. / The operation fertilization accounts for a significant portion of the costs of agricultural production. Improve the quality of this operation entails economic and environmental benefits. The process of fertilization is usually performed at an average rate representative of an area, however, the chemical properties of soil can vary considerably within the area. Thus, some locations may receive fertilizer and / or lime in excess, while others may receive insufficient amounts. The alternative is to average the application to perform variable rate, characterized by applying inputs according to the specific requirements within the area. For this application happens, metering mechanisms control the application. The aim of this study is to evaluate the dosing mechanisms of a truck hauling fertilizer, locks and mats, meet the requirements of the prescribed dose map fertilizer recommendation. To evaluate the uniformity of operation used the statistical process control. According to the obtained results it can be stated that the meter mechanism did not meet the condition to perform variable rate application to uniformly.

In the recent past precision farming has become increasingly popular amongfarmers. However, little has been done to study the business aspect of precision farming,with most research focusing on the production side. This purpose of this thesis is tostudy the feasibility of successfully opening and operating a precision farming firm inKentucky. To determine the feasibility of such a venture a computer model was createdand a producer survey was designed and distributed to farmers in Western and CentralKentucky.The purpose of the computer model was to determine the factors that wouldinfluence the successful operation of a precision farming firm including number of acresserviced per year, pricing of services, the cost of capital to borrow money, and manyother factors. A break-even analysis was performed to determine what kind of annualincreases in business would be required, what price range services should be in, and atwhat interest rate money could be borrowed and a simulated precision farming firm couldstill operate successfully.The producer survey was mailed to 336 farmers in Western and Central Kentuckybecause of their geographical locations and the type of crops that are grown there. Thesurvey response rate was 20 percent and of the 66 surveys that were returned 59 wereappropriate and useful for research. After compiling the results of the surveys,regressions were run to determine any correlation between dependent and independentvariables that affect the adoption rate of precision farming techniques. The results foundthat a negative correlation exists between age adoption rates of precision farming and thata positive correlation exists between farm size and adoption rates of precision farming.After conducting the research, it is believed that given the right economicconditions and management a precision farming firm is very capable of thriving inKentucky. However, the workforce must be very motivated and capable of constantlyrecruiting new clients to adopt precision farming.

Master of Science / Department of Agronomy / Antonio R. Asebedo / Johanna A. Dille / Field experiments were conducted in 2016 and 2017 across nine locations in Kansas to develop and evaluate a procedure for variable-rate applications (VRA) of soil-applied herbicides in corn and grain sorghum based on soil properties. Soil electrical conductivity (EC) and soil organic matter (SOM) data were collected at each location using a Veris MSP3. Soil EC was correlated to soil texture and herbicide algorithms were developed for two different tank-mixes for corn and for grain sorghum. Three algorithms were evaluated in the field for each tank-mix based only on SOM (alg-SOM), SOM and soil texture (alg-SOMtex), or a flat rate based on the average soil properties for the entire field. Rates for each tank-mix were based on the maximum usage rate (MUR) allowed. When soil variability across a field was adequate, VRA based on algorithms were effective at five of the nine locations. Across these five locations, alg-SOM resulted in the same or better weed control at 8 weeks after treatment (WAT) compared to the flat rate and reduced herbicide use by 12% for both tank-mixes in grain sorghum. Using alg-SOMtex reduced herbicide use by 24% in grain sorghum, but had less weed control at several locations compared to the flat rate. VRA was practical at Morganville, KS in 2017. Both alg-SOM and alg-SOMtex increased the amount of herbicide applied compared to the flat rate, but alg-SOMtex resulted in greater Palmer amaranth control (92%) compared to the flat rate (71%). Separate greenhouse and field experiments were conducted in 2017 to evaluate the activity of soil-applied herbicides on controlling HPPD-inhibitor resistant Palmer amaranth populations. A dose-response greenhouse experiment of soil-applied mesotrione and isoxaflutole was performed using resistant (Stafford County) and susceptible (Riley County) Palmer amaranth populations. Reduced susceptibility was observed with resistant-to-susceptible ratios being 7.2 for mesotrione and 4.1 for isoxaflutole. Field experiments were conducted at two locations in KS with one field having HPPD-resistant (Barton County) and the other HPPD-susceptible (Reno County) Palmer amaranth populations. Treatments were three HPPD-inhibiting herbicides [mesotrione (¼X, ½X, and 1X = 210 g ha-1), isoxaflutole (½X and 1X = 105 g ha-1), and bicyclopyrone (1X = 50 g ha-1 and 2X in formulated tank-mix with bromoxynil at 700 and 1400 g ha-1)] in comparison to other soil-applied herbicides commonly used for Palmer amaranth control. HPPD-inhibitor treatments were applied alone and tank-mixed with atrazine (2240 g ha-1). Overall, control of Palmer amaranth was reduced for HPPD-resistant compared to -susceptible populations. All treatments of mesotrione and isoxaflutole at 4 WAT resulted in 81 to 99% control in Reno County, but only 55 to 89% control in Barton County. For mesotrione and isoxaflutole treatments across both sites, Palmer amaranth control at 4 WAT was greater when 1X was applied (89%) compared to 0.5X (81%). Tank-mixing atrazine with mesotrione and isoxaflutole increased Palmer amaranth control from 82 to 88%. Soil-applied HPPD-inhibitors were most effective when applied at field usage rate in combination with atrazine for both populations. When using soil-applied HPPD-inhibitors, management recommendations should be the same regardless of Palmer amaranth population.

A operação de adubação responde por parte significativa dos custos de produção agrícola. Melhorar a qualidade dessa operação acarreta benefícios econômicos e ambientais. O processo de adubação normalmente é realizado a uma taxa média, representativa de uma área, no entanto, propriedades químicas do solo podem variar consideravelmente dentro dessa área. Desse modo, alguns locais poderão receber fertilizantes e/ou corretivos em excesso, enquanto outros poderão receber quantidades insuficientes. A alternativa à taxa média é a realizar a aplicação à taxa variada, que se caracteriza por aplicar os insumos de acordo com as necessidades específicas dentro da área. Para que essa aplicação aconteça, mecanismos dosadores controlam a aplicação. O objetivo deste estudo é avaliar os mecanismos dosadores de uma carreta adubadora de arrasto, comportas e esteiras, atendem as prescrições de doses previstas no mapa de recomendação de adubação. Para avaliar a uniformidade da operação utilizou-se o controle estatístico do processo. De acordo com os resultados obtidos pode-se afirmar que os mecanismos dosadores não atenderam a condição de realizar a aplicação à taxa variável de maneira uniforme. / The operation fertilization accounts for a significant portion of the costs of agricultural production. Improve the quality of this operation entails economic and environmental benefits. The process of fertilization is usually performed at an average rate representative of an area, however, the chemical properties of soil can vary considerably within the area. Thus, some locations may receive fertilizer and / or lime in excess, while others may receive insufficient amounts. The alternative is to average the application to perform variable rate, characterized by applying inputs according to the specific requirements within the area. For this application happens, metering mechanisms control the application. The aim of this study is to evaluate the dosing mechanisms of a truck hauling fertilizer, locks and mats, meet the requirements of the prescribed dose map fertilizer recommendation. To evaluate the uniformity of operation used the statistical process control. According to the obtained results it can be stated that the meter mechanism did not meet the condition to perform variable rate application to uniformly.

Weeds typically grow in patches across agricultural landscapes. Because of this characteristic growth pattern, it seems logical to apply herbicides site-specifically to control them. To do this effectively, methods must be identified to accurately map weed presence and make cost effective herbicide application decisions to control them. The primary objective of this research was to develop a site-specific herbicide decision support system. Additional objectives include evaluating the effects of sampling patterns and interpolation techniques for weed mapping accuracy and evaluating texture analysis for weed patch detection in row-crops. A geographic information system (GIS) extension was developed to work in conjunction with a commercial software component for calculating site-specific herbicide applications based on user input weed maps. Results of the extension were compared to that of the commercial software. The GIS extension was able to accurately develop herbicide options based on the given weed densities and potential net return for treatment of the weeds in any specific area of the field. Sampling techniques and interpolation methods were compared to assess the accuracy of each pattern/method combination. The patterns used in this study were the W- and Z-shaped pattern, and the interpolation methods used were kriging and inverse distance weighted. Neither the pattern nor method impacted the results of the predicted average values for a given weed species. The last objective addressed was texture analysis? ability to distinguish weed patches in row-crops. Texture analysis was also tested to determine its ability to distinguish between areas requiring a herbicide application and areas not requiring a herbicide application. The analysis was performed on 3 vegetative indices and the NIR band of multispectral imagery at three different spatial resolutions (0.14 m, 0.5 m, and 1 m), and for two dates in the growing season. Texture analysis performed better on late season for both scenarios, with the highest classification accuracies (45 to 75%) coming from distinguishing areas that were below a given weed threshold from those that were above.

Devido à existência de variabilidade espacial nos fatores que afetam o desenvolvimento do algodoeiro, faz-se necessário investigar a hipótese de que existem diferenças na dose de máximo retorno econômico da aplicação de nitrogênio (N) em cobertura e de fitorreguladores em áreas de cultivo de algodão. Assim, esse trabalho teve como objetivo investigar o potencial da utilização de sensores ativos de dossel para detecção da variabilidade espacial do desenvolvimento das plantas e da nutrição nitrogenada existente em áreas de produção de algodão, bem como estabelecer estratégias de gestão da variabilidade com o uso de taxas variáveis na adubação nitrogenada de cobertura e na aplicação de fitorreguladores no algodoeiro. Foram conduzidos experimentos em áreas comerciais de cultivo do algodoeiro localizadas em Chapadão do Céu - GO nas safras 2012/2013 e 2013/2014 e em Campo Verde - MT na safra 2014/2015. Avaliou-se o desempenho de dois modelos de sensores ativos de dossel em predizer a altura de plantas e o acúmulo de biomassa e N no algodoeiro, considerando dois sistemas de produção (espaçamento convencional e adensado) e vários estádios de desenvolvimento da cultura. Foram instaladas parcelas para calibração das curvas de dose resposta do algodoeiro ao nitrogênio em cobertura em diferentes condições de desenvolvimento da cultura relacionadas a variações no solo ou no histórico de produtividades no interior do talhão. Com base nos resultados dos experimentos foram desenvolvidos e validados algoritmos para aplicação em taxas variáveis de N e fitorreguladores, adotando-se o conceito de experimentos em nível de fazenda, com o modelo estatístico considerando a condutividade elétrica do solo como uma covariável e uma matriz de variância-covariância espacial, que foi ajustada pelo método da máxima verossimilhança. O desempenho geral dos sensores foi satisfatório, sendo capazes de predizer a altura de plantas e o acúmulo de biomassa e N no algodoeiro com valores de R2 acima de 0,90. Observou-se interação significativa com o espaçamento das fileiras e a fase de desenvolvimento da cultura, com performance inferior em situações de pequena variabilidade na cultura ou de acúmulo de biomassa muito grande. A resposta do algodoeiro ao nitrogênio aplicado em cobertura variou de acordo com as condições de cultivo de cada experimento. Maiores respostas foram observadas em áreas de médio e baixo potencial produtivo, existindo talhões e partes de talhões em que a aplicação de N não proporcionou incremento de produtividade, enquanto que em outras áreas observou-se aumento de produtividade expresso por uma relação quadrática entre a dose aplicada e a produtividade. No talhão com as maiores diferenças, a dose de máximo retorno econômico foi de 0 kg ha-1 na região de alto potencial produtivo, 165 kg ha-1 na região de médio potencial produtivo e 280 kg ha-1 na região de baixo potencial produtivo. Na análise dos experimentos em nível de fazenda, o melhor ajuste foi obtido no modelo que considera a dependência espacial dos resíduos, evidenciando que em experimentos dessa dimensão não se deve assumir que os princípios da estatística clássica são sempre satisfeitos. Em três áreas não foram observadas diferenças significativas entre a aplicação do N em cobertura em taxa fixa ou usando os algoritmos para aplicação em taxa variável, devido à homogeneidade da área e da interferência de outros fatores. Em uma das áreas observou-se vantagem para a aplicação em taxas variáveis usando o algoritmo que recomenda aplicação de maiores doses de N nos locais em que as plantas apresentam menor desenvolvimento vegetativo, com produtividade cerca de 100 kg ha-1 que a aplicação em taxa fixa e cerca de 300 kg ha-1 superior à obtida com a aplicação em taxas variáveis usando o algoritmo que recomenda aplicação de maiores doses de N nos locais em que as plantas apresentam-se mais vigorosas. A aplicação de fitorreguladores em taxas variáveis não apresentou efeito significativo na produtividade de algodão em caroço, entretanto o volume consumido dos produtos foi em média 18% menor na aplicação em taxa variável, principalmente em função das áreas que não foram aplicadas por apresentarem desenvolvimento vegetativo reduzido. / Due to the existence of spatial variability in factors affecting cotton development, it is necessary to investigate the hypothesis that there are differences in the economic optimum fertilizer rates of top dressing nitrogen (N) and plant growth regulators (PGR) applications in cotton fields. Thus, the objective of this study was to investigate the potential of using active crop canopy sensors to detect the spatial variability of plant development and nitrogen nutrition in cotton fields and to establish strategies for managing spatial variability using variable rate technology to apply N and PGR in cotton. We conducted experiments in commercial cotton production fields located in the state of Goiás, in 2012/2013 and 2013/2014 seasons, and in the state of Mato Grosso, in 2014/2015 season. We evaluated the performance of two models of active crop canopy sensors to predict the height of plants and the accumulation of biomass and N in cotton, considering two production systems (conventional and narrow row spacing) and various growth stages. Within-field variations in the response curve to the increasing doses of nitrogen was evaluated under different crop development conditions related to variations in soil and historical yields. Based on the results of the experiments we developed and validated algorithms for variable rate application of N and PGR, using on-farm experiments. The statistical model considered the soil electrical conductivity as a covariate and a spatial variance-covariance matrix, which was adjusted by maximum likelihood. The overall performance of the sensors was satisfactory, predicting the height of plants and the accumulation of biomass and N in cotton with R2 values above 0.90. There was a significant interaction with the row spacing and the development stage of the crop, with lower performance in situations of low variability or very large biomass accumulation. The cotton response to top dressing nitrogen varied according to growing conditions of each experiment. Major responses were observed in areas of medium and low yield potential. There were fields and plots within fields in which the application of N did not increased yields, while in other areas there was a quadratic relationship between the dose applied and yield. In the field with the biggest differences, the economic optimum fertilizer rates of top dressing N was 0, 165 and 280 kg ha-1 in the high, medium and low yield potential zones, respectively. In the analysis of on-farm experiments, the best fit was obtained in the model that considered the spatial dependence of the residues, showing that experiments of this size we should not assume that the principles of classical statistics are always satisfied. In three areas, there was no significant differences between the application of N in fixed rate or using the algorithms for variable rate application, due to the homogeneity of the areas and the interference of external factors. In one of the areas, there was an advantage for application at variable rates using the algorithm that recommends application of higher doses of N in places where the plants have low vegetative development. The yields were about 100 kg ha-1 higher than the application of a fixed rate and 300 kg ha-1 higher than that obtained with the application of variable rates using the algorithm that recommends applying higher doses of N in places where the plants were more vigorous. The variable rate application of PGR had no significant effect on cottonseed yield, however the amount of products used was on average 18% lower in the variable rate application, mainly due to the not applied areas.

Devido à existência de variabilidade espacial nos fatores que afetam o desenvolvimento do algodoeiro, faz-se necessário investigar a hipótese de que existem diferenças na dose de máximo retorno econômico da aplicação de nitrogênio (N) em cobertura e de fitorreguladores em áreas de cultivo de algodão. Assim, esse trabalho teve como objetivo investigar o potencial da utilização de sensores ativos de dossel para detecção da variabilidade espacial do desenvolvimento das plantas e da nutrição nitrogenada existente em áreas de produção de algodão, bem como estabelecer estratégias de gestão da variabilidade com o uso de taxas variáveis na adubação nitrogenada de cobertura e na aplicação de fitorreguladores no algodoeiro. Foram conduzidos experimentos em áreas comerciais de cultivo do algodoeiro localizadas em Chapadão do Céu - GO nas safras 2012/2013 e 2013/2014 e em Campo Verde - MT na safra 2014/2015. Avaliou-se o desempenho de dois modelos de sensores ativos de dossel em predizer a altura de plantas e o acúmulo de biomassa e N no algodoeiro, considerando dois sistemas de produção (espaçamento convencional e adensado) e vários estádios de desenvolvimento da cultura. Foram instaladas parcelas para calibração das curvas de dose resposta do algodoeiro ao nitrogênio em cobertura em diferentes condições de desenvolvimento da cultura relacionadas a variações no solo ou no histórico de produtividades no interior do talhão. Com base nos resultados dos experimentos foram desenvolvidos e validados algoritmos para aplicação em taxas variáveis de N e fitorreguladores, adotando-se o conceito de experimentos em nível de fazenda, com o modelo estatístico considerando a condutividade elétrica do solo como uma covariável e uma matriz de variância-covariância espacial, que foi ajustada pelo método da máxima verossimilhança. O desempenho geral dos sensores foi satisfatório, sendo capazes de predizer a altura de plantas e o acúmulo de biomassa e N no algodoeiro com valores de R2 acima de 0,90. Observou-se interação significativa com o espaçamento das fileiras e a fase de desenvolvimento da cultura, com performance inferior em situações de pequena variabilidade na cultura ou de acúmulo de biomassa muito grande. A resposta do algodoeiro ao nitrogênio aplicado em cobertura variou de acordo com as condições de cultivo de cada experimento. Maiores respostas foram observadas em áreas de médio e baixo potencial produtivo, existindo talhões e partes de talhões em que a aplicação de N não proporcionou incremento de produtividade, enquanto que em outras áreas observou-se aumento de produtividade expresso por uma relação quadrática entre a dose aplicada e a produtividade. No talhão com as maiores diferenças, a dose de máximo retorno econômico foi de 0 kg ha-1 na região de alto potencial produtivo, 165 kg ha-1 na região de médio potencial produtivo e 280 kg ha-1 na região de baixo potencial produtivo. Na análise dos experimentos em nível de fazenda, o melhor ajuste foi obtido no modelo que considera a dependência espacial dos resíduos, evidenciando que em experimentos dessa dimensão não se deve assumir que os princípios da estatística clássica são sempre satisfeitos. Em três áreas não foram observadas diferenças significativas entre a aplicação do N em cobertura em taxa fixa ou usando os algoritmos para aplicação em taxa variável, devido à homogeneidade da área e da interferência de outros fatores. Em uma das áreas observou-se vantagem para a aplicação em taxas variáveis usando o algoritmo que recomenda aplicação de maiores doses de N nos locais em que as plantas apresentam menor desenvolvimento vegetativo, com produtividade cerca de 100 kg ha-1 que a aplicação em taxa fixa e cerca de 300 kg ha-1 superior à obtida com a aplicação em taxas variáveis usando o algoritmo que recomenda aplicação de maiores doses de N nos locais em que as plantas apresentam-se mais vigorosas. A aplicação de fitorreguladores em taxas variáveis não apresentou efeito significativo na produtividade de algodão em caroço, entretanto o volume consumido dos produtos foi em média 18% menor na aplicação em taxa variável, principalmente em função das áreas que não foram aplicadas por apresentarem desenvolvimento vegetativo reduzido. / Due to the existence of spatial variability in factors affecting cotton development, it is necessary to investigate the hypothesis that there are differences in the economic optimum fertilizer rates of top dressing nitrogen (N) and plant growth regulators (PGR) applications in cotton fields. Thus, the objective of this study was to investigate the potential of using active crop canopy sensors to detect the spatial variability of plant development and nitrogen nutrition in cotton fields and to establish strategies for managing spatial variability using variable rate technology to apply N and PGR in cotton. We conducted experiments in commercial cotton production fields located in the state of Goiás, in 2012/2013 and 2013/2014 seasons, and in the state of Mato Grosso, in 2014/2015 season. We evaluated the performance of two models of active crop canopy sensors to predict the height of plants and the accumulation of biomass and N in cotton, considering two production systems (conventional and narrow row spacing) and various growth stages. Within-field variations in the response curve to the increasing doses of nitrogen was evaluated under different crop development conditions related to variations in soil and historical yields. Based on the results of the experiments we developed and validated algorithms for variable rate application of N and PGR, using on-farm experiments. The statistical model considered the soil electrical conductivity as a covariate and a spatial variance-covariance matrix, which was adjusted by maximum likelihood. The overall performance of the sensors was satisfactory, predicting the height of plants and the accumulation of biomass and N in cotton with R2 values above 0.90. There was a significant interaction with the row spacing and the development stage of the crop, with lower performance in situations of low variability or very large biomass accumulation. The cotton response to top dressing nitrogen varied according to growing conditions of each experiment. Major responses were observed in areas of medium and low yield potential. There were fields and plots within fields in which the application of N did not increased yields, while in other areas there was a quadratic relationship between the dose applied and yield. In the field with the biggest differences, the economic optimum fertilizer rates of top dressing N was 0, 165 and 280 kg ha-1 in the high, medium and low yield potential zones, respectively. In the analysis of on-farm experiments, the best fit was obtained in the model that considered the spatial dependence of the residues, showing that experiments of this size we should not assume that the principles of classical statistics are always satisfied. In three areas, there was no significant differences between the application of N in fixed rate or using the algorithms for variable rate application, due to the homogeneity of the areas and the interference of external factors. In one of the areas, there was an advantage for application at variable rates using the algorithm that recommends application of higher doses of N in places where the plants have low vegetative development. The yields were about 100 kg ha-1 higher than the application of a fixed rate and 300 kg ha-1 higher than that obtained with the application of variable rates using the algorithm that recommends applying higher doses of N in places where the plants were more vigorous. The variable rate application of PGR had no significant effect on cottonseed yield, however the amount of products used was on average 18% lower in the variable rate application, mainly due to the not applied areas.

Master of Science / Department of Biological & Agricultural Engineering / Robert E. Wolf / Traditionally, growers spray uniform application of pesticides over the target area regardless of variations in pest infestations. In recent years, variable rate application (VRA) technologies have made it possible to apply pesticides in variable rates across the field. In pesticide application, nozzles play a vital role. In general, pesticides are applied using conventional nozzles. Most conventional nozzles vary flow rates only over a 2:1 range when operated within the recommended pressure range due to a fixed spray orifice. Conventional nozzles vary droplet sizes tremendously when there are speed and application rate changes which results in inefficient application. Conventional nozzles have limitations when used for VRA. A new nozzle called Varitarget nozzle (U.S. Patent No. 5,134,961) was developed and marketed by Bui, (2005) to overcome the limitations with conventional nozzles. Varitarget nozzles have a variable orifice that changes in size in response to pressure changes, allowing varying flow rates with a minimal change in droplet size. Laboratory tests and field tests were conducted to study the performance of Varitarget nozzle. Varitarget black/blue and clear/yellow caps were evaluated in this study. Lab studies were conducted to measure Varitarget characteristics compared to conventional nozzles. The flow rate ratios of Varitarget nozzle black and clear caps were 12:1 and 10:1 while the conventional nozzles produced flow rate ratios ranging from only 3:1 to 4:1. The measured flow rate of Varitarget nozzle black and clear caps was similar to that published by the manufacturer up to 40 psi and varied higher after 40 psi. Both Varitarget black and clear cap nozzle was within the standard VMD requirements until 40 psi and showed increasing trend while the conventional nozzles matched the standard VMD requirements. The VT black and clear cap nozzles showed better coverage at higher pressures when compared to conventional nozzles. CV values for VT black and clear capped nozzles were less than 10% which indicates capability of good uniform distribution. Spray angle of 110 degrees for VT black and clear capped nozzles was consistent over a range of pressures. Field studies were also conducted to compare the Varitarget to conventional nozzles. In the varying speed study, droplet size varied from 498 to 621 microns with a SD of 47.50 for VT black nozzle and 465 to 599 microns with a SD of 54.08 for VT clear cap nozzle as the speed varied from 4 to 12 mph. In the varying application rate study, The droplet size varied from 432 to 510 microns with a SD of 27.84 for VT black nozzle and 355 to 452 microns with a SD of 39.80 as the application rate varied from 4 to 12 GPA. In both studies, the observed pressure range required for spraying was minimum and varied slightly.

<p>Soil residual herbicides are a vital component of the best management practices (BMPs), to provide early-season weed control in most cropping systems. The availability of a biologically effective dose of a soil residual herbicide in the soil solution is dependent on several soil parameters including soil texture, organic matter (OM), and pH.  Soil residual herbicides are currently applied as a uniform application rate over an individual field; yet soil properties can vary spatially within agricultural fields. Therefore, areas of the field are being over- and under-applied when using a uniform application rate. By integrating variable-rate (VR) technology with soil residual herbicides, the correct rate could be applied based on the intra-field soil variability. However, the extent of spatial soil variability within a field and the impact on herbicide application rates has not been well-characterized to inform whether soil residual herbicide applications should move towards variable rate applications. Therefore, the objectives of this research were to 1) determine the extent of intra-field variability of soil texture and organic matter in ten commercial Indiana fields, 2) quantify the reliability of five different combinations of spatial soil data sources, 3) determine the impact of soil sample intensity on map development and the classification accuracy for VR applications of soil residual herbicides, 4) quantify the impact of VR herbicide application on the total amount and spatial accuracy of herbicide applied according to product labels, and 5) determine if the intensive spatial characterization of soil properties is related to weed seedbank abundance and species richness to improve predictive weed management using soil residual herbicides.</p> <p><br></p> <p>Commercial soil data was generated by intensively collecting 60 soil samples in a stratified random sampling pattern in 10 agricultural fields across Indiana. Analysis of this data from commercial fields confirmed inherent field variability that would benefit from multiple management zones according to the labeled rate structures of pendimethalin, s-metolachlor, and metribuzin. Therefore, further research was conducted to determine an accurate and reliable method to delineate the fields into management zones for variable-rate residual herbicide applications based on the spatial soil variability and herbicide labels. </p> <p><br></p> <p>A modified Monte Carlo cross-validation method was used to determine the best source of spatial soil data and sampling intensity for delineating management zones for variable-rate applications of pendimethalin, s- metolachlor, and metribuzin. These sources of spatial soil data included: Soil Survey Geographic database (SSURGO) data, intensive soil samples, electrical resistivity sensors, and implement mounted optical reflectance sensors using VNIR reflectance spectroscopy. The mean management zone classification accuracy for maps developed from soil samples with and without electrical conductivity was similar for 75% of all maps developed across each field, herbicide, and sampling intensity. The method of using soil sampling data combined with electrical conductivity (SSEC) maps was most frequently the top performing source of spatial soil data. The most reliable sampling intensity was one sample per hectare which resulted in lower root mean squared error (RMSE) OM values, higher management zone classification accuracy, and more reliable predictions for the number of management zones within each field. </p> <p><br></p> <p>Using VR maps developed from SSEC with one sample per hectare sampling intensity, additional research was conducted to compare the amount of herbicide and field area that was over-or under-applied with a uniform application rate compared to a VR application for 10 corn and soybean residual herbicides. Although research from our previous study documented that spatial soil variability was extensive enough to require two or more management zones for all fields, the same labeled herbicide dose defined for multiple soil conditions led to 20% of all maps not requiring a variable rate application (VRA). Additionally, no difference was shown in the total amount applied of herbicide in an individual field between a variable and uniform application rate for all herbicides. Nonetheless, nearly half of all VR maps had 10% or more of the field area misapplied with a uniform application rate and justifies further research to determine if the proper placement of residual herbicide adds value through increased weed control in the field areas being under-applied. </p> <p><br></p> <p>Similar to soil residual herbicides, weed seedbank abundance and species richness were impacted by the variable soil conditions present within the field area. The seedbanks favor the establishment in areas of the field that promote vigorous germination, growth, and reproduction next to the competing crop. Therefore, soil sampling and weed seedbank greenhouse grow-outs were conducted in four fields to gain a better understanding in the relationship between the spatial soil and weed seedbank variability. All weed seedbank characteristics were shown to be spatially aggregated. Even though no individual or combination of soil parameters consistently explained the variability of weed seedbank abundance, species richness, or individual weed species across all four fields. However, clay content was the most persistent soil parameter to negatively impact (lower seedbank values) the soil weed seedbank.</p> <p><br></p> <p>Further field studies should be conducted across multiple sites to determine if variable-rate residual herbicide applications aid farmers by reducing the risk of crop injury in over-applied field areas and increased weed control in the areas being under-applied.  These studies should also access whether earlier emergence and/or greater weed densities occur in field areas receiving sublethal herbicide doses compared to areas receiving the optimal application rate. Additional research should investigate the utility of VR residual herbicide applications when tank-mixing multiple products during an application. Particularly, when the soil parameters used for selecting the herbicide rate are not defined the same across herbicide labels </p>

In Anbetracht des Kompromisses zwischen der Erzielung des höchsten Gewinns und der geringsten Umweltbelastung ist ein tiefes Verständnis der ökonomischen Folgen der Stickstoff (N) Düngung erforderlich. Die vorliegende Doktorarbeit liefert umfassende Einblicke in (i) die Auswirkungen des standortspezifischen N-Managements (SSNM) auf die Rentabilität und Risikominderung, (ii) die Auswirkungen von Unsicherheiten und Risikoeinflüssen auf optimale N-Düngergaben und (iii) das Potenzial und die Kosten der Vermeidung von Treibhausgas (THG) Emissionen durch N-Düngereduktion. Ein Modellierungsansatz wurde entwickelt, um die Wirkung von Ertrag und Proteingehalt, Wirtschafts- und Risikoauswirkungen sowie THG-Emissionen auf die N-Düngung zu simulieren. Die Ergebnisse der Arbeit zeigen, dass SSNM die Wirtschaftlichkeit verbessert, indem es eine höhere Weizenqualität und damit Preisprämien erzielt. SSNM reduziert das Risiko, die Backqualität nicht zu erreichen, und es gibt keine wesentlichen Nachteile beim Verlustrisikomanagement im Vergleich zum einheitlichen Management. Preisprämien für eine höhere Weizenqualität bieten Anreize für höhere N-Düngergaben. Prämien verflachen die Gewinnfunktion weiter, was unzureichende Argumente für eine Absenkung des N-Inputs aus der Wirtschaftlichkeitssicht liefert, selbst bei einer hohen Risikoaversion der Landwirte. Eine moderate Reduzierung der mineralischen N-Düngung kann die THG-Emissionen bei moderaten Opportunitätskosten mindern. Die THG-Vermeidung durch N-Düngereduktion in einer bestimmten Region kann unter Berücksichtigung kultur- und ertragszonenspezifischer Ertragswirkungen optimiert werden. Insgesamt liefert diese Arbeit wichtige Erkenntnisse über die Chancen und Nachteile der Anpassung der N-Düngergaben. Darüber hinaus leistet sie einen direkten Beitrag zur Identifizierung von kosten- und risikoeffizienten N-Managementoptionen und bildet die Grundlage für effektive politische Ansätze zur THG-Vermeidung durch selektive N-Düngereduktion. / Considering the tradeoff between achieving the highest profit and causing the lowest environmental impact, there is a need for a profound understanding of the economic consequences of nitrogen (N) fertilizer application. The present doctoral research provides comprehensive insights into (i) effects of site-specific N management (SSNM) on profitability and risk mitigation; (ii) impacts of uncertainties and risk implications on optimal N fertilizer rates; and (iii) potential and costs of mitigating greenhouse gas (GHG) emissions by N fertilizer reduction. A modelling approach was developed to simulate the response of yield, protein, economic and risk implications, and GHG emissions to N fertilizer application. Findings of the thesis show that SSNM improves profitability by achieving higher grain quality, thus, price premiums. SSNM reduces the risk of not reaching the baking grain quality and poses no considerable disadvantage on downside risk management compared to uniform management. Price premiums for higher wheat quality provide incentives for higher N input rates. Premiums further flatten the profit function, giving insufficient arguments for lowering N input from a farm profitability perspective, even in presence of high risk aversion of farmers. Moderate reduction of mineral N fertilizer can mitigate GHG emissions at moderate opportunity costs. GHG mitigation by N fertilizer reduction in a given region can be optimized considering crop and yield-zone-specific yield responses. Overall, this thesis provides important insights on chances and drawbacks of adjusting N fertilizer rates. Moreover, it makes a direct contribution in identifying cost- and risk-efficient N management options and provides a basis for effective policy approaches to reduce GHG emissions by selective N fertilizer reduction.