O milho (Zea mays) é considerado como uma das culturas mais importantes cultivadas mundialmente devido a sua composição química, valor nutritivo e o seu potencial produtivo, apresentando assim, considerável relevância nos aspectos socioeconômicos. Diversos fatores interferem no desempenho da cultura e, dentre eles, o clima está entre aqueles que oferecem os maiores desafios para planejamento e manejo da cultura. Diante da importância da cultura no contexto nacional e mundial, é importante considerar as projeções futuras da produção do grão diante das mudanças climáticas e, consequentemente, na segurança alimentar nos próximos anos. Assim, avaliou-se neste estudo o impacto da mudança do clima sobre o crescimento e desenvolvimento da cultura do milho, utilizando um modelo de crescimento de plantas, baseado em processos biofísicos. Para a calibração do modelo foram utilizados dados obtidos experimentalmente e a simulação de cenários de mudanças climáticas foi realizada de acordo com a abordagem do programa AgMIP. Trabalhou-se com o modelo CERES-MAIZE/DSSAT, e três modelos de circulação climática global (GCM\'s) regionalizados e dois cenários econômicos (ou de emissão) para o período 2040-2069 (representando 2050). Com base nos resultados obtidos, pode-se concluir que se as práticas de gestão se mantêm como presentes, o rendimento de milho deverá diminuir em meio do século, no entanto, a diminuição dos rendimentos reais pode não ser tão dramática quanto previsto nos casos em que apenas o fator climático é considerado. Para isso fatores econômicos e tecnológicos devem ser considerados para aumentar os rendimentos. O aumento da [CO2] terá um efeito positivo sobre o crescimento do cultivo, mas não parece ser suficiente para compensar os efeitos negativos do clima futuro, notadamente o aumento da temperatura do ar. / Maize (Zea mays) is considered one of the most important crops cultivated worldwide due to its chemical composition, nutritional value and its productive potential, thus presenting considerable relevance in socioeconomic aspects. Several factors interfere in the performance of the crop and, among them, the climate is among those that offer the greatest challenges for crop planning and management. Given the importance of culture in the national and global context, it is important to consider the future projections of grain production in the face of climate change and, consequently, food security in the coming years. Thus, the impact of climate change on maize crop growth and development was evaluated in this study using a plant growth model based on biophysical processes. For the calibration of the model, data obtained experimentally were used and the simulation of climate change scenarios was performed according to the AgMIP program approach. We worked with the CERES-MAIZE / DSSAT model, and three regional climate circulation models (GCM\'s) and two economic (or emission) scenarios for the period 2040-2069 (representing 2050). Based on the results obtained, it can be concluded that if management practices remain as present, corn yields should decrease in the middle of the century, however, the decrease in real incomes may not be as dramatic as predicted in cases where that only the climatic factor is considered. For this economic and technological factors must be considered to increase incomes. The increase in [CO2] will have a positive effect on crop growth, but it does not appear to be sufficient to compensate for the negative effects of future climate, notably the increase in air temperature.

O milho (Zea mays) é considerado como uma das culturas mais importantes cultivadas mundialmente devido a sua composição química, valor nutritivo e o seu potencial produtivo, apresentando assim, considerável relevância nos aspectos socioeconômicos. Diversos fatores interferem no desempenho da cultura e, dentre eles, o clima está entre aqueles que oferecem os maiores desafios para planejamento e manejo da cultura. Diante da importância da cultura no contexto nacional e mundial, é importante considerar as projeções futuras da produção do grão diante das mudanças climáticas e, consequentemente, na segurança alimentar nos próximos anos. Assim, avaliou-se neste estudo o impacto da mudança do clima sobre o crescimento e desenvolvimento da cultura do milho, utilizando um modelo de crescimento de plantas, baseado em processos biofísicos. Para a calibração do modelo foram utilizados dados obtidos experimentalmente e a simulação de cenários de mudanças climáticas foi realizada de acordo com a abordagem do programa AgMIP. Trabalhou-se com o modelo CERES-MAIZE/DSSAT, e três modelos de circulação climática global (GCM\'s) regionalizados e dois cenários econômicos (ou de emissão) para o período 2040-2069 (representando 2050). Com base nos resultados obtidos, pode-se concluir que se as práticas de gestão se mantêm como presentes, o rendimento de milho deverá diminuir em meio do século, no entanto, a diminuição dos rendimentos reais pode não ser tão dramática quanto previsto nos casos em que apenas o fator climático é considerado. Para isso fatores econômicos e tecnológicos devem ser considerados para aumentar os rendimentos. O aumento da [CO2] terá um efeito positivo sobre o crescimento do cultivo, mas não parece ser suficiente para compensar os efeitos negativos do clima futuro, notadamente o aumento da temperatura do ar. / Maize (Zea mays) is considered one of the most important crops cultivated worldwide due to its chemical composition, nutritional value and its productive potential, thus presenting considerable relevance in socioeconomic aspects. Several factors interfere in the performance of the crop and, among them, the climate is among those that offer the greatest challenges for crop planning and management. Given the importance of culture in the national and global context, it is important to consider the future projections of grain production in the face of climate change and, consequently, food security in the coming years. Thus, the impact of climate change on maize crop growth and development was evaluated in this study using a plant growth model based on biophysical processes. For the calibration of the model, data obtained experimentally were used and the simulation of climate change scenarios was performed according to the AgMIP program approach. We worked with the CERES-MAIZE / DSSAT model, and three regional climate circulation models (GCM\'s) and two economic (or emission) scenarios for the period 2040-2069 (representing 2050). Based on the results obtained, it can be concluded that if management practices remain as present, corn yields should decrease in the middle of the century, however, the decrease in real incomes may not be as dramatic as predicted in cases where that only the climatic factor is considered. For this economic and technological factors must be considered to increase incomes. The increase in [CO2] will have a positive effect on crop growth, but it does not appear to be sufficient to compensate for the negative effects of future climate, notably the increase in air temperature.

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Crop simulation models (CSMs) are used to evaluate management and environmental scenarios on crop growth and yields. Two corn (Zea Mays L.) crop growth simulation models, Hybrid-Maize, and CERES-Maize were calibrated and validated under Virginia conditions with the goal of better understanding corn response to variable environmental conditions and decreasing temporal yield variation. Calibration data were generated from small plot studies conducted at five site-years. Main plots were plant density (4.9, 6.2, 7.4, and 8.6 plants m-2); subplots were hybrids of differing relative maturity (RM) [early = Pioneer® Brand "34B97" (108 day RM); medium = Pioneer® Brand "33M54" (114 day RM); and late = Pioneer® Brand "31G66" (118 day RM)]. Model validation was generated from large scale, replicated strip plot trials conducted at various locations across Virginia in 2005 and 2006. Prior to model adjustments based on calibration data, both CSMs under predicted corn grain yield in calibration and validation studies. CERES-Maize grain yield prediction error was consistent across the range of tested plant density while accuracy of Hybrid-Maize varied with plant density. Hybrid-Maize-estimated biomass production was highly accurate. Greater leaf area index (LAI) and biomass production were measured than was predicted by the CERES-Maize CSM. Both CSMs were modified based on calibration data sets and validated. Validation results of the calibrated CSMs showed improved accuracy in simulating planting date and environmental effects on a range of corn hybrids grown throughout Virginia over two years. We expect that both modified models can be used for strategic research and management decisions in mid-Atlantic corn production. / Master of Science

Master of Science / Department of Agronomy / Scott A. Staggenborg / Irrigated cropping systems on the High Plains are dominated by water intensive continuous corn (Zea mays L.) production, which along with other factors has caused a decline in the Ogallala aquifer. Potentially demand for water from the aquifer could be decreased by including drought tolerant crops, like grain sorghum (Sorghum bicolor L.) and cotton (Gossypium hirsutum L.), in the cropping systems. This study calibrated the CERES-Maize, CERES-Sorghum, and CROPGRO-Cotton models for the High Plains and studied the simulated effects of different irrigation amounts and initial soil water contents on corn, cotton, and grain sorghum. Input files for calibration were created from irrigated and dryland research plots across Kansas. Information was collected on: soil physical properties, dry matter, leaf area, initial and final soil water content, management, and weather. CERES-Maize simulated grain yield, kernel number, ear number, and seed weight across the locations with root mean square errors (RMSE) of 2891 kg ha-1, 1283 kernels m-2, 1.6 ears m-2, and 38.02 mg kernel-1, respectively. CERES-Sorghum simulated grain yield, kernel number, head number, and seed weight with RMSEs of 2150 kg ha-1, 5755 kernels m-2, 0.13 heads m-2, and 4.51 mg kernel-1. CROPGRO-Cotton simulated lint yield and boll number with RMSEs of 487 kg ha-1 and 25.97 bolls m-2. Simulations were also conducted with CERES-Maize, CERES-Sorghum, and CROPGRO-Cotton to evaluate the effects of irrigation amounts and initial soil water content on yield, evapotranspiration (ET), water use efficiency (WUE), available soil water at maturity, and gross income per hectare. Simulations used weather data from Garden City, KS from 1961 to 1999. Irrigation amounts were different for all variables for corn and grain sorghum. For cotton, yield, WUE, soil water, and gross income were not different between the top two irrigation amounts. For corn and grain sorghum, initial soil water content was only different at 50% plant available water. Initial soil water had no affect on cotton, except for ET at 50%. Simulations showed that cotton yields are similar at lower irrigation. Also, cropping systems that include cotton have the potential to reduce overall irrigation demand on the Ogallala aquifer, potentially prolonging the life of the aquifer.