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Organic food products are produced without synthetic chemicals, including herbicides, pesticides, and fertilizers. Food grown in organic systems that are certified organic by the United States Department of Agriculture command a price premium, whether it is direct to consumer via farmers markets or in conventional grocery stores. Organic food and food products are representing a relatively larger portion of overall food sales in recent years, and the demand for organic meat has also increased. However, there is a lack of available U.S.-grown organic grains and soybeans to feed the growing number of organic certified livestock to produce organic meat to meet this demand. This shortage results from many factors, yet is primarily due to organic production requirements for significantly more land and operating capital when compared to conventionally grown counterparts. There is a lack of information detailing the relative costs and returns of organic grain production, and, limited understanding of organic premiums. The overall goal of this study is to examine differences in price levels between organic and conventional corn, soybeans, wheat, oats, and barley between 2007 and 2015, as well as factors that may affect the organic premium. For organic grain and soybean producers, study findings reveal that the least risky organic commodities to grow include corn and soybeans, especially if sold in the cash market. However, the author suggests that growers may consider growing wheat, barley, and oats if they have a buyer willing to contract in advance to ensure a premium and reduce price risk. For purchasers of organic grains and soybeans, including major food companies as well as livestock producers, it is recommended they continue to study developments in organic grain supplies as producers continue to consider adoption of organic production methods. / Master of Science

This thesis consists of two research papers, each of which studies the benefits from a different College of Agriculture and Life Sciences (CALS) program. These analyses provide necessary information to allocate resources efficiently among programs. The first paper studies the Virginia Quality Assured feeder cattle certification program and its effects on feeder cattle prices and profitability. No significant effect on price from VQA certification is found. However, enterprise budgets indicate that VQA cattle allow higher farm profits due to their lower sale weight, which allows for faster turnover and lower prices. The second paper studies the benefits to producers from wheat and barley breeding conducted by Virginia Tech researchers. Variety trial data are combined with acreage estimates constructed from royalty data to estimate gains from replacement of old varieties with new ones. The study finds that the program generated benefits to producers of over $119 million between 2000 and 2018. / Master of Science / This thesis contains two papers that assessed the benefits of two agricultural research and extension programs at Virginia Tech. The first paper studies the Virginia Quality Assured certification program. This program certifies cattle that have been raised following practices that are designed to result in cattle that will grow faster and stay healthier in a feedlot. Statistical analysis of cattle sold through a Virginia telephone auction show that VQA certified cattle do not receive higher prices than uncertified cattle, but the analysis also finds that certified and uncertified cattle have important physical differences, including lighter weights for certified cattle. These lighter weights make it possible for farmers to sell more VQA cattle in a year because they spend less time gaining weight before being sold, giving producers of VQA cattle the opportunity for higher profits per year. The second paper studies the benefits to farmers from wheat and barley breeding by Virginia Tech researchers. Field trials are used to compare the yields of old and new varieties, and acreage estimates are used to show how newer varieties replace older ones in farmers' fields. The study finds that economic benefits to farmers from new varieties released by the program total $119 million from 2000 to 2018.

The objective of this study is to evaluate the costs of reducing pesticide, nitrogen, phosphorus, and sediment losses of a representative risk-neutral and risk-averse peanut-cotton farmer in Southeast Virginia. Five currently popular rotations and eight alternative conservation rotations are evaluated for the representative farm. The Erosion-Productivity Impact Calculator (EPIC) model is used to simulate pesticide, nitrogen, phosphorus, and soil loss from each rotation using actual rainfall and temperature data from the study area. A Target-MOTAD mathematical programming model, REPVAFARM, is developed and solved with GAMS. The objective of the farmer is to maximize expected net return, while meeting a target income with certain allowable expected shortfall from the income target. The farmer is also constrained by land, labor, peanut quota, and levels of pesticide, nitrogen, phosphorus, and soil losses. Major findings of this study are: reducing pesticide, nitrogen, phosphorus, and soil losses imposes costs to the farmer regardless of his risk attitude, with costs ranking from high to low in the order of reducing all pollutant losses, reducing nitrogen losses, reducing phosphorus losses, reducing soil losses, and reducing pesticide losses. Costs of reducing pollutant losses are higher for more risk-averse farmers than for less risk-averse and risk-neutral farmers implying that risk-aversion is an obstacle to the adoption of alternative conservation practices. Reducing pesticide losses has little impact on other pollutants. Reducing pesticide and nitrogen losses simultaneously achieves similar reductions in soil loss and phosphorus loss. / Master of Science

Manure injection is an alternative manure application method that places manure in subsurface bands rather than spreading it evenly across the soil surface as done with the typical broadcasting method. The reduced exposure of manure to air under injection can lead to greater N retention when compared to broadcasting, but also alters the spatial distribution of manure. This altered spatial distribution of manure could alter soil nutrient dynamics and crop growth; however, literature exploring this subject is limited. Therefore, this dissertation aimed to compare soil nitrate and active carbon levels between manure injection and broadcasting, assess the spatial distribution of soil N under injection, and determine if the subsurface bands under injection cause differential crop growth. An 8-site on-farm study was conducted comparing spring manure applications under corn silage. This study found that soil NO3-N was the same under injection and broadcasting but did alter the spatial distribution of soil NO3-N as it was consistently elevated in the injection band compared to between bands. No differences in active carbon were observed, even when measuring the injection band directly. This finding calls into question the usefulness of measuring active carbon in manured systems. Corn silage yields were only significantly increased at 1 of 8 sites, and this occurred at the one site that did not receive a sidedress N application, which suggests that N was not limiting at the other seven sites. A small-scale research plot study examining fall manure applications under small grains found similar results to the previous study. No consistent differences in soil NO3-N were observed between injected, broadcast, and control plots; however, soil NO3-N was greater in the injection band compared to between, a difference that persisted for two months after manure application. Evidence of soil NO3-N leaching was observed in one study year, suggesting soil NO3-N leaching under fall manure applications should be examined. No consistent differences in soil active carbon were observed, either between manure application methods or injection bands. Furthermore, the alteration in soil NO3-N under injection did not lead to differential small grain growth. A 24 site on-farm study was conducted to assess potential differential growth of small grains following manure injection. This study found that soil NO3-N in the manure injection band compared to between bands was significantly increased in 13 of 24 sites and was on average 137% greater in-band at the 0-15 cm depth. This difference did not persist through small grain silage harvest as only 1 of 24 sites showed a significant difference in-band. Small grain maturity did not show any difference in 2021 due to late planting dates, but some differences were observed in the injection band compared to between bands one month after planting. As with soil NO3-N, these differences did not persist through silage harvest. Small grain forage quality parameters were not different in-band compared to between-band at harvest, while DM yield only differed in 3 of 24 sites, with 2 of those 3 sites being under wheat. The data presented in this dissertation indicates that manure injection causes differential soil NO3-N levels from banding. Accurately measuring soil NO3-N levels under injection was difficult due to the injection band being difficult to fully sample and suggests injected soil NO3-N levels were underestimated. No meaningful changes in crop growth were observed due to banding or different manure application methods. / Doctor of Philosophy / Manure injection is a more environmentally friendly method of manure application when compared to traditional surface broadcasting. While research is clear on the environmental benefits of manure injection, the agronomic benefits of injection are unclear. Therefore, this research aimed to compare soil nitrogen and crop response to manure injection. Manure injection did not result in consistently increased corn or small grain yields when compared to manure broadcasting. Soil nitrate was not typically altered between manure application methods, but this could have been due to our soil sampling method not sampling enough of the manure injection band. Manure injection did result in soil nitrate being concentrated in the area manure was injected. The elevated soil nitrate in the area manure was injected typically persisted 1-2 months after manure application but didn't persist to the end of the growing season. This early season increase in soil nitrate concentrations in the manure injection area did not result in differential small grain maturity in both a small-scale research plot study and a 24 site on-farm study. Three of 24 sites studied showed increased small grain yield when comparing the area manure was injected compared between injection bands, with two of these three sites being under wheat. This suggests small grain yield response to manure injection bands could be species dependent.

Nous avons tous l'intuition qu'un travail peut être réalisé en beaucoup moins de temps s'il est réparti entre plusieurs personnes ou sur plusieurs machines. Cette notion se nomme le parallélisme qui peut se définir comme l'état de ce qui se développe dans la même direction ou en même temps. C'est naturellement que la notion de parallélisme a été appliquée aux ordinateurs. De ce fait, il a été possible de répondre aux besoins de puissance nécessaire à la réalisation de projets gourmands en temps de calculs et en taille mémoire. Le parallélisme combiné à une algorithmique performante permet de gagner du temps afin de répondre au mieux à d'importants besoins. Il rompt avec l'approche classique qui consiste à gagner de la vitesse en effectuant plus rapidement chaque opération, approche bornée par les lois de la physique. La notion de parallélisme a donc grandement contribué à la multiplication des modèles informatiques. <br /><br />Nous nous intéresserons au modèle systolique et au modèle parallèle à gros grains baptisé (Coarse Grained Multicomputers). Le modèle CGM a été proposé par F. Dehne et al. et il possède des propriétés qui le rendent très intéressant d'un point de vue pratique. Il est parfaitement adapté à la modélisation des architectures existantes pour lesquelles le nombre de processeurs peut être de plusieurs milliers et la taille des données peut atteindre plusieurs milliards d'octets. Un algorithme développé pour ce modèle est constitué de calculs locaux utilisant, si possible, des algorithmes séquentiels optimaux et de rondes de communication dont le nombre doit être indépendant de la taille des données à traiter. Le modèle CGM est donc très intéressant d'un point de vue économique. En effet, ce modèle est indépendant des architectures réelles et permet de réutiliser des algorithmes séquentiels efficaces, ce qui le rend très portable. <br /><br />Dans cette thèse nous nous intéressons à des problèmes d'algorithmique du texte. Ces problèmes peuvent améliorer la compression de données ou bien être utilisés en bio-informatique. Ainsi, nous proposons des solutions CGM aux problèmes de recherche de la plus longue sous-suite croissante, de la plus longue sous-suite commune à deux mots, du plus long suffixe répété en chaque caractère d'un mot et de répétitions. Pour cela, nous sommes partis de solutions systoliques existantes que nous avons adaptées au modèle CGM. Le but de ce travail est en fait double. D'une part, nous proposons pour la première fois des solutions CGM à ces quatre problèmes. D'autre part, nous montrons comment des solutions systoliques peuvent être dérivées en algorithmes CGM. En effet, de nombreux problèmes ont été étudiés sur des architectures systoliques, c'est à dire des machines dédiées, non réutilisables pour d'autres problèmes. Le modèle CGM quant à lui permet de travailler avec des machines peu coûteuses et réutilisables à souhaits. De plus, l'expérience acquise au cours de ces travaux nous permet d'avoir une bonne idée des solutions systoliques adaptables au modèle CGM. Ceci pourrait permettre de consolider le pont existant entre modèles à grains fins et modèles à gros grains. <br /><br />Nous finissons cette thèse par une discussion sur l'équilibrage de charge des solutions proposées et sur la prédictivité de l'adaptation d'autres solutions systoliques au modèle CGM.

O presente estudo analisa, numa perspectiva mais ampla, as principais características do novo tempo do Cerrado. Estas estão intimamente relacionadas à propagação dos fronts agrícolas, ou seja, da agricultura moderna, a partir da década de 1970. Esta agricultura, realizada de maneira intensiva e em larga escala, introduziu nos cerrados brasileiros um novo tempo, ao implantar sistemas técnicos extremamente funcionais à produção agrícola moderna, permitindo às grandes empresas um maior domínio da produção. Dentre os sistemas técnicos controlados pelas empresas, o sistema de armazenamento se destaca, ao configurar-se como um dos principais elos logísticos dos diversos circuitos espaciais produtivos agrícolas. Os silos permitem cadenciar a circulação dos grãos no tempo e no espaço, sendo imprescindíveis desde a produção (strictu sensu), até os estágios finais de exportação e consumo. Nos fronts agrícolas, o controle do sistema de armazenamento se torna ainda mais estratégico, por se tratar da principal região produtora de grãos do país, pela grande distância com relação aos portos exportadores e regiões consumidoras e pela precariedade dos sistemas de transporte. Esse contexto torna a posse do sistema de armazenamento um elemento chave para o controle da produção. É por isso que nas principais regiões produtoras a posse dos sistemas de armazenamento é ainda mais seletiva, sendo controlada pelas grandes firmas processadoras e exportadoras de grãos, tornando os produtores e o Estado subservientes à política das empresas. Portanto, esta pesquisa analisa de maneira mais estrita como o domínio do sistema de armazenamento de grãos confere às empresas um maior poder de regulação da produção agrícola e um uso privilegiado do território. / The present work intends to analyze, in an ampler perspective, the main characteristics of the new time of the Cerrado. These are closely related to the propagation of fronts agricultural, that is, of modern agriculture, from the decade of 1970s. This agriculture, carried through in intensive way and on a large scale, introduced in the brazilian Cerrado a new time, when implanting extremely functional technical systems to the modern agricultural production, allowing to the great companies a bigger domain of the production. Among the controlled technical systems by the companies, the storage system detaches, when configuring itself as one of the main logistic links of the diverse space circuits productive agricultural. The silos allow to canry on the circulation of the grains in the time and the space, it has been essential since the production (strictu sensu), until the final periods of training of exportation and consumption. In the agricultural fronts, the control of the storage system becomes still more strategical, for dealing with the main producing region of grains of the country, for the great distance recated to the exporter ports and consumer regions and for the precariousness of the transport systems. This context has become the ownership of the storage system an important element for the control of the production. It is for this reason that in the main productive regions the ownership of the storage systems is still more selective, and controlled for the tradings, becoming the producers and the State servile the politics of the companies. Therefore, this research analyzes in way more strict how the domain of system grains storage confers to the companies a bigger power of regulation of the agricultural production and a privileged use of the territory.