Masters of Science / Department of Agricultural Economics / Jeffrey M. Peterson / The expansion of the biofuels industry, world demand, and various other factors are having a historic impact on the price of grains. These high prices have been creating a large increase in production of many water intensive crops such as corn. As corn is among the most input-intensive crops, this extra production has raised concerns about environmental impacts and pressures on water resources in particular. While water quality has been a longstanding concern in the cornbelt, much of the new production is in nontraditional corn regions including the southeast, the High Plains, and the western states. In these areas, there is mounting concern over depletion of already stressed water supplies. In the High Plains, the chief water source is the Ogallala aquifer, one of the largest water resources in the world that underlies eight states from South Dakota to Texas. The Ogallala has enabled many agricultural industries, such as irrigated crops, cattle feeding, and meat processing, to establish themselves in areas that would not be possible otherwise. A consequence is that the economy of this region has become dependent on groundwater availability. Continued overdrafts of the aquifer have caused a long-term drop in water levels and some areas have now reached effective depletion. This thesis seeks to estimate the impact of the rising commodity prices on groundwater consumption and cropping patterns in the Kansas portion of the Ogallala. The economy of this region is particularly dependent on water and irrigated crops, with more than 3 million head of feeder cattle and irrigated crop revenues exceeding $600 million annually. Sheridan (northwestern Kansas), Seward (southwestern Kansas), and Scott (west central Kansas) counties have been selected as representative case study regions. These counties have a wide range of aquifer levels with Seward having an abundant supply, Sheridan an intermediate supply, and Scott nearing effective depletion. Cropping patterns in these counties are typical of the western Kansas region, with most irrigated acreage being planted to corn and with dominant nonirrigated rotations of wheat-fallow and wheat-sorghum-fallow. A Positive Mathematical Programming (PMP) model was developed and calibrated to land- and water-use data in the case counties for a base period of 1999-2003. The PMP approach produces a constrained nonlinear optimization model that mimics the land- and water- allocation decision facing producers each year. The choice variables in the model are the acreages planted to each of the major crops and the water use by crop. The model was run for each of the case counties. The PMP calibration procedure ensures that the model solutions fall within a small tolerance of the base period observations. Once calibrated, the models were executed to simulate the impacts of the emerging energy demand for crops over a 60-year period. After the baseline projections were found, the model was then run under increased crop prices that reflect the higher prices observed in 2006 and after. The thesis found that under the high price scenario, both irrigated crop production and water application per acre increased significantly during the early years of the simulated period in all modeled counties. The size of the increases depended on the amount of original water available in each county. The increases generally diminished in magnitude toward the end of the simulation period, but led to smaller ending levels of saturated thickness as compared to the base price in all counties. Finally, in two of the three counties, it was observed that initial increases in irrigated crop acres and water application forces a decline in the aquifer such that less water can be applied per acre in the final years of the simulation. This suggests that high commodity prices forces a higher emphasis on early production levels than later production levels. Additionally, the higher prices have a significant effect on the rate of decline of the Ogallala aquifer.

[ES] A escala mundial, la Citricultura es uno de los sectores dentro de la Fruticultura con mayor producción, superando los 158 millones de toneladas en el año, pero es sensible de un gran número de estreses abióticos al ser un cultivo subtropical. La baja temperatura es uno de los estreses abióticos que más afecta a los cítricos produciendo grandes pérdidas anuales. El cambio climático está muy presente dando lugar cambios en los patrones de El tiempo originando un gran número de olas de frío y calor. Pero gracias a la técnica del injerto y al uso de patrones de cítricos los problemas causados por los estreses abióticos pueden mejorarse. El IVIA cuenta con un programa de mejora de patrones cuyo objetivo es la búsqueda de nuevo material vegetal con el fin de satisfacer los problemas de la citricultura. Tradicionalmente, el patrón más tolerante a la baja temperatura es Poncirus trifoliata, el cual se han realizado la mayoría de los trabajos en la bibliografía. Como patrón sensible, se empleó Citrus macrophylla ya que se trata de un patrón del tipo limonero que se sabe popularmente de su sensibilidad al frío. También se empleó el patrón citrange Carrizo, el cual se trata de patrón comercial más cultivado en España en la actualidad y la variedad Taroco Rosso, que se sabe de su pigmentación a causa de la baja temperatura. Así pues, los capítulos planteados en la presente tesis fueron: 1. Estrés a baja temperatura a corto plazo, 2. Estrés a baja temperatura a largo plazo y 3. El efecto del patrón en la variedad Tarocco Rosso. / [CAT] A escala mundial, la Citricultura és un dels sectors dins de la Fruticultura amb més producció, superant els 158 milions de tones a l'any, però és sensible d'un gran nombre d'estressos abiòtics per ser un cultiu subtropical. La baixa temperatura és un dels estressos abiòtics que més afecta els cítrics produint grans pèrdues anuals. El canvi climàtic està molt present donant lloc a canvis en els patrons de El temps originant un gran nombre d'onades de fred i calor. Però gràcies a la tècnica de l'empelt i a l'ús de patrons de cítrics, els problemes causats pels estressos abiòtics es poden millorar. L'IVIA compta amb un programa de millora de patrons que te com a objectiu la recerca de nou material vegetal per tal de satisfer els problemes de la citricultura. Tradicionalment, el patró més tolerant a la baixa temperatura és Poncirus trifoliata, el qual s'han realitzat la majoria dels treballs a la bibliografia. Com a patró sensible, es va fer servir Citrus macrophylla ja que es tracta d'un patró del tipus llimoner que se sap popularment de la seva sensibilitat al fred. També es va emprar el patró citrange Carrizo, el qual es tracta del patró comercial més cultivat a Espanya actualment i la varietat Taroco Rosso, que se sap de la seva pigmentació a causa de la baixa temperatura. Així doncs, els capítols plantejats en aquesta tesi van ser: 1. Estrès a baixa temperatura a curt termini, 2. Estrès a baixa temperatura a llarg termini i 3. L'efecte del patró en la varietat Tarocco Rosso. / [EN] On a global scale, Citriculture is one of the sectors within Fruit Growing with the highest production, exceeding 158 million tons per year, but it is sensitive to many abiotic stresses as it is a subtropical crop. Low temperature is one of the abiotic stresses that most affects citrus, producing large annual losses. Climate change is very present, giving rise to changes in weather patterns, causing many cold and heat waves. But thanks to the grafting technique and the use of citrus rootstocks, problems caused by abiotic stresses can be improved. IVIA institute has a rootstock improvement program whose objective is to search for new plant material to satisfy the problems of Citriculture. Traditionally, the most low-temperature tolerant rootstock is Poncirus trifoliata, on which most of the work in the literature has been done. As a sensitive rootstock, Citrus macrophylla was used since it is a lemon type rootstock that is popularly known for its sensitivity to cold. The citrange Carrizo rootstock was also used, which is currently the most cultivated commercial rootstock in Spain, and the Taroco Rosso variety, which is known for its pigmentation due to low temperature. Thus, the chapters proposed in this thesis were: 1. Short-term low-temperature stress, 2. Long-term low-temperature stress, and 3. The rootstock effect on the Tarocco Rosso variety. / Primo Capella, MA. (2023). Caracterización fisiológica y molecular de la respuesta de patrones de cítricos a estrés por baja temperatura [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192892