Master of Agribusiness / Department of Agricultural Economics / Kevin Dhuyvetter / This thesis was commissioned by Cooperative Producers, Inc. (CPI) of Hastings, Nebraska in order to better understand the preferences and uses of precision agriculture by customers within the company’s trade territory. With the rapid increase of precision agriculture (hardware, software, services, etc.) it is necessary to get a better understanding of what drives growers to adopt and implement precision agriculture practices. A paper survey was sent out in CPI’s monthly statements to patrons that also included instructions to be able to fill out an online survey if that was preferred. From that offering there were a total of 114 responses providing data from which several technology adoption models were estimated. Based on prior experience with precision agriculture and the development of services offered to growers, it is hypothesized that there are three primary variables influencing a grower’s decision to adopt precision agriculture. If the operation is managed by a younger grower (<40 years old), farms with a larger number of acres, and if a high percent of the operation’s acres are irrigated they will be more likely to adopt precision agriculture practices. The survey results generally revealed that younger farmers, larger farm size, and a higher percentage of irrigated acres did not increase the likelihood of utilizing precision agriculture. The questions asked in the survey were designed to provide information for the development of a tool that salespeople offering precision agriculture services could use to determine if a potential customer with be inclined to adopt and utilize precision agriculture. While some of the results were contrary to expectations they do offer insight into what type of customer adopts precision agriculture and a direction for CPI to move in order to maximize market penetration.

Plant canopy sensors have emerged as a new tool for in field on-the-go spatially localized prediction of plant biomass and nitrogen (N) uptake by crops in an indirectly and plant indestructible way as base for N variable rate fertilization. Sensors based on the combination of specific reflectance bands from the electromagnetic spectrum constitute the vast majority of canopy sensors, and this principle has already been validated in many crops. Alternatively to this concept, the use of ultrasonic distance sensors to measure crop canopy height has been presented as an option to estimate biomass. Based on that, the aim of this thesis was to validate and refine canopy sensor systems on automated diagnosis of plant parameters aimed the application of N fertilizer according sugarcane needs. Therefore, it was necessary to: 1) validate the prior calibration made for the reflectance sensor (Portz et al., 2012) and to establish the best time to use the sensor over the crop; 2) test the use of the reflectance sensor in comparative strips trials of uniform and sensor based N variable rate application testing algorithms with positive and negative slope and measuring productivity at the end of the season; 3) obtain the relationship between crop canopy height with accumulated biomass and N uptake by the crop during the initial growing season; 4) explore the plant height measured with an ultrasonic sensor comparing the results of biomass and N uptake prediction with those obtained with the reflectance sensor. The experiments were conducted on commercial sugarcane fields, and in strips of the crop with N variable rate application. The experiments were installed over clayey and sandy soils in dry and rainy seasons being all evaluated with the reflectance sensor Yara N-Sensor model ALS (N-Sensor&reg; ALS, Yara International ASA) and partly in comparison with an ultrasonic sensing system Polaroid 6500 (Polaroid, Minnetonka, MN, USA), when the crop had stalk height between 0.2 and 0.9 m. The reflectance sensor calibration fitted with the previous published data showing the interval between 0.3 - 0.5m as the most appropriate to use this sensor over sugarcane. The positive slope algorithm was superior to the negative, except in the situation of clayey soil in rainy season where the response from the negative slope algorithm was higher. The sugarcane plant height was highly correlated with biomass and N uptake by the crop, being possible to estimate the plants canopy height indirectly by the use of an ultrasonic sensor. Comparing the sensor systems, canopy reflectance was better in the early stages of crop as canopy height was more suitable for estimating the cultural parameters when the plants already covered soil in between the rows (+ 0.6 m stalk height), being the sensor systems complementary when fertilization is widely spread in the early crop growth period. / Sensores de dossel tem se apresentado como uma nova ferramenta para a predição espacialmente localizada, em tempo real, de forma indireta e indestrutiva da biomassa vegetal e extração de nitrogênio (N) pelas culturas como base para a aplicação de fertilizantes nitrogenados em taxas variáveis. Sensores baseados na combinação de faixas específicas de reflectância do espectro eletromagnético constituem a grande maioria dos sensores de dossel sendo este princípio já validado para uso em muitas culturas. Alternativamente a este conceito, a medição da altura do dossel cultural com o uso de sensor ultrassónico se apresenta como uma alternativa para a estimativa de biomassa vegetal. Com base nisso o objetivo desta tese foi de validar e aperfeiçoar sistemas sensores para a automação do diagnóstico visando à aplicação de fertilizante nitrogenado em função da necessidade da cana-de-açúcar. Para tanto, foi necessário: 1) validar a previa calibração feita ao sensor de reflectância (PORTZ et al., 2012) assim como estabelecer o melhor momento para uso do sensor na cultura; 2) ensaiar o uso do sensor em faixas comparativas entre taxa fixa e variável testando algoritmos de aplicação com inclinação positiva e negativa para dose de N mensurando produtividade; 3) obter a relação entre altura de dossel da cultura com, biomassa acumulada e extração de nitrogênio pela planta; 4) explorar a altura de plantas mensurada com um sensor ultrassónico comparando os resultados de predição de biomassa e extração de nitrogênio com aqueles obtidos com sensor de refletância. Os experimentos foram conduzidos em talhões comerciais de cana-de-açúcar e em forma de faixas da cultura, com aplicação em taxa variada de doses de N. Os experimentos foram instalados em solos de textura argilosa e arenosa nas épocas seca e chuvosa do ano sendo todos avaliados com o sensor Yara N-Sensor, modelo ALS (N-Sensor&reg; ALS, Yara International ASA), e em parte comparando com um sistema sensor ultrassónico Polaroid 6500 (Polaroid, Minnetonka, MN, EUA) quando a cultura apresentava altura de colmos entre 0,2 e 0,9 m. Os dados coletados para a calibração do sensor de reflectância se encaixaram exatamente aos dados já publicados mostrando-se o intervalo entre 0.3 e 0.5 m o mais indicado ao uso deste sensor. O algoritmo com inclinação positiva se mostrou superior ao negativo exceto na situação de solo argiloso em estação chuvosa onde a resposta do algoritmo negativo foi maior. A altura de planta de cana-de-açúcar se mostrou altamente correlacionável com biomassa e extração de nitrogênio pela cultura, sendo possível estimar a altura do dossel das plantas de forma indireta pelo uso do sensor ultrassónico. Comparando-se os sistemas sensores, reflectância de dossel se mostrou melhor em estádios iniciais da cultura enquanto altura de dossel se mostrou mais indicada para estimar os parâmetros culturais quando as plantas já recobriam as entrelinhas (+0.6 m colmo), mostrando-se os sistemas sensores complementares quando o período de fertilização for mais amplo na fase inicial da cultura.

Thesis advisor: Fabio Ghironi / Thesis advisor: Matteo Iacoviello / This dissertation studies the implications of housing market heterogeneity for the trans- mission of shocks, welfare and the conduct of monetary policy. In the first chapter I focus on mortgage contract heterogeneity (fixed vs. variable-rate mortgages). I develop and solve a New Keynesian dynamic stochastic general equilibrium model that features a housing market and a group of constrained individuals who need housing collateral to obtain loans. A given proportion of constrained households borrows at a variable rate, while the rest borrows at a fixed rate. The model predicts that in an economy with mostly variable-rate mortgages, an exogenous interest rate shock has larger effects on borrowers than in a fixed-rate economy. For plausible parametrizations, aggregate differences are muted by wealth effects on labor supply and by the presence of savers. More persistent shocks cause larger aggregate differences. From a normative perspective I find that, in the presence of collateral constraints, the optimal Taylor rule is less aggressive against inflation than in the standard sticky-price model. Furthermore, for given monetary policy, a high proportion of fixed-rate mortgages is welfare enhancing. Then, I develop a two-country version of the model to study the implications of housing market heterogeneity for a monetary union as well as costs and benefits of being in a monetary union when there are asymmetric shocks. Results show that consumption reacts more strongly to common shocks in countries with high loan-to-value ratios (LTVs), a high proportion of borrowers or variable-rate mortgages. I also find that country-specific housing price shocks increase consumption not only in the country where the shock takes place. Welfare analysis shows that housing-market homogeneization is not beneficial per se, only when it is towards low LTVs or predominantly fixed-rate mortgages. As for costs and benefits of monetary unions, when there is a technology shock in one of the countries and they are symmetric, the monetary union regime is welfare worsening. However, results are dependent on whether or not countries are symmetric and on the source of the asymmetry. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

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.

Variable-rate technologies for sprayer applications stand to increase efficacy by ensuring the right amount of chemical is applied at the right location. However, external environmental factors such as droplet drift caused by variable ambient condition, are not yet integrated into modern sprayer systems. Real-time wind velocity measurements can be used to control droplet spectra for reducing spray drift by actuating a variable-orifice nozzle. This work aimed to develop data processing methods needed to filter noise and remove vehicle speed from wind velocity measurements collected with an ultrasonic anemometer aboard a moving platform. Using a global navigation satellite system (GNSS), vehicle speed was calculated in the field and subtracted from apparent wind velocity for comparison to static measurements. Experiments under stationary and dynamic sensor deployments were used to develop an algorithm to provide instantaneous local wind velocity and to better understand the local spatiotemporal variability of wind under field conditions.

The feasibility of using optical sensors and non-nitrogen limiting reference crops to determine post-emergent nitrogen fertilizer requirements of canola was evaluated. Normalized difference vegetation index was well suited for estimating yield potential and nitrogen status. Although sensor-based nitrogen management was generally agronomically feasible for canola, the economic benefits of doing so remain uncertain because of the added cost of applying post-emergent nitrogen. / February 2008

The heavy rainfall, gentle to severe topography with high proportion of bare spots, and weed patches emphasize the need of variable rate split (VRS) fertilization in wild blueberry. Two commercial fields were selected in central Nova Scotia to evaluate the impact of VRS fertilization on ammonia volatilization, subsurface water quality, and crop productivity. Management zones were delineated based on slope variability, and different fertilizer rates were applied using global positioning system (GPS) guided prescription map. Ammonia huts were used to quantify the ammonia volatilization losses, while the lysimeters were installed in the fields to evaluate the impact of different fertilizer treatments on subsurface water quality. The VRS treatment significantly decreased the ammonia volatilization losses and nutrients leaching losses as compared to uniform treatment. Based on the results of this study, it can be concluded that VRS fertilization in wild blueberry fields could reduce environmental contamination and improve crop productivity.

Two wild blueberry fields were selected in central Nova Scotia, to characterize and quantify the spatial pattern of variability in soil properties, leaf nutrients and fruit yield, identification of yield influencing soil properties, and to develop management zones for site-specific fertilization. A combination of classical statistics, geostatistical analysis and mapping in Arc GIS 9.3 indicated substantial variation within field. The stepwise regression suggested that the soil EC, horizontal co-planar geometry (HCP), inorganic nitrogen and moisture content were major yield influencing factors. The cluster analysis of the soil variables with the fruit yield also indicated that HCP, inorganic nitrogen, EC, SOM, and ?v were closely grouped with the fruit yield at a similarity level greater than 70%. Based on the results of this study the wild blueberry fields can be divided into different management zones for variable rate fertilization to improve crop production, increase revenue, and reduce potential environmental contamination.

Two wild blueberry fields were selected to evaluate the impact of variable rate (VR) fertilization on crop productivity, surface and subsurface water quality. Management zones were delineated based on slope variability, and different fertilizer rates were applied according to prescription maps. Runoff collectors were place in the fields to measure the nutrient losses in surface runoff, while lysimeters were installed to evaluate the impact of VR fertilization (VRF) on subsurface water quality. The VR treatment significantly decreased phosphorus and nitrogen loadings in surface runoff as compared to uniform treatment. The concentrations of nutrients in subsurface water samples were also significantly lower for VR treatment as compared to uniform treatment. The excessive nutrients enhanced vegetative growth in low lying areas of uniform fertilization, while berry yield was less. Based on these results, it can be concluded that VRF in wild blueberry fields improved the crop productivity and potential environmental impacts. / This study was conducted to evaluate the impact of variable rate fertilization on crop productivity and surface and subsurface water quality in wild blueberry fields. Result illustrated that variable rate fertilization significantly reduce the nutrients loading in surface and subsurface water, and improved blueberry yield.

We present a new sub-optimal near-maximum-likelihood (ML) detection method for the family of variable-rate space-time block codes (VRSTBC). The proposed detection method is based on the concept of symbol reliability and provides a wide range of performance-complexity trade-offs. The reliability measures are defined with the help of a recent generic ML metric expression. The error performance and complexity analysis of the method via simulations show an achievable near-ML error performance with significant reduction in complexity. The performance of the proposed method is also compared with the group interference cancellation (GIC) method which was the detection method originally applied to VRSTBCs and the results show a significant improvement. The new method offers various levels of error protection via a simple parameter and hence can provide the users of a wireless network with different performance levels according to their cost allowance. Unequal error protection by VRSTBCs under the new detection method was explored. Several applications integrating data with different levels of sensitivity to error can benefit from the wide range of possibilities that the combination of the proposed detection method and VRSTBCs provides. To further explore these flexibilities, four practically interesting power allocation schemes were applied to the transmission and the behaviors were observed through case studies. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-09-26 23:45:07.81