RESUMODeficiência hídrica é considerada a maior restrição na produção e estabilidade da produtividade de culturas em muitas regiões do mundo. No Estado de Goiás, região na qual predomina a produção em sequeiro, para a cultura do milho (Zea mays L.) implantada na safra normal e na safrinha, é comum sofrer períodos de estresse por deficiência hídrica intermitente ou terminal, que reduzem o rendimento de grãos. No processo de desenvolvimento de novos híbridos e variedades cultivadas, genótipos são selecionados em função de sua adaptabilidade em um determinado ambiente alvo. Assim, programas de melhoramento vegetal, com o objetivo de desenvolver híbridos e variedades cultivadas mais adaptados a um determinado ambiente, requerem informações sob a probabilidade de ocorrência dos diferentes tipos de deficiência hídrica, como também, suas características, intensidade e tempo, em função da fase fenológica da cultura. Um modelo de simulação de culturas foi utilizado para determinar os padrões de deficiência hídrica no estado de Goiás, considerando 12 locais e 6 diferentes datas de semeadura para a cultura do milho semeada na safra normal e na safrinha. Para a cultura do milho semeado na safra normal, a perda na produtividade decorrente do estresse por deficiência hídrica foi menor que 50%, sendo que os tipos de deficiência hídrica que provocam um maior impacto na produtividade iniciam-se no começo do período reprodutivo. Para o milho semeado na safrinha, a perda na produtividade é superior a 50%, sendo mais comum o estresse terminal, que tem sua maior intensidade no enchimento de grãos. Termos para indexação: Modelos de crescimento, Zea mays, cerrado, veranico, estresse hídrico. ABSTRACTWater stress is a major constraint to crop production and yield stability in many regions of the world. The cultivation of corn (Zea mays L.) in the Brazilian State of Goiás, is frequent affected by periods of water stress resulting in yield reduction. During the process of developing new hybrids and cultivated varieties, new genotypes are selected based on their adaptability for a certain environment. In this context, plant breeding programs demand for information regarding as a function of the crop phenological phases. A crop simulation model was used to determine patterns of water stress for 12 locations of the State of Goiás and 6 different sowing for both, first and second corn harvest periods. For the first harvest period, yield loss due to water stress was lower than 50%, with higher effects on yield in the beginning of the reproductive period. For corn as a second crop, yield loss is higher than 50% with frequent occurrence of terminal stress, which presented higher intensity during the stage of grain filling.

kg ha-1 N application (first year) and of 14,86 t ha-1 with 177 kg ha-1 N dose (second year). The increases in the production of green ears were not due to increases in the number of ears per area and by length of these. Differently of husked ear/husk ratio, the average weights of the husked and unhusked ears and diameter of unhusked ears were affected by N application. It was proposed a table of recommended N doses based on pre-established prices of N and commercial ears.

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Abstract Abstract: The objective of this work was to evaluate the relations between soil water content and the soil bulk dielectric constant, and to study different waveguides of a TRASE soil water content analyzer that operates according to TDR principles. Non-destructive and destructive samples of two sites of different texture of a Dystrophic Yellow Latossol were collected and packed into 10 L containers, resulting in four replications for each texture and structure. Three different waveguides were built with rods of 0.15 m length, one with a capacitor at the beginning of the waveguide, one without a capacitor, with rods 0.009 m apart, and another without a capacitor, with rods 0.022 m apart. These waveguides, together with buriable standard ones supplied by tne manufactures with 0.20 m rods 0.022 m apart, were inserted in each sample. Soil water content was obtained by gravimetry and estimated by the TRASE analyzer, based on soil bulk dielectric constants using all waveguides during the soil drying process with water contents changing from 0.35 m

Irrigation use constitutes an alternative to improve maize production in Central Minas Gerais State, Brazil. However, even under adequate water supply conditions, other environmental factors may influence maize crop growth and development and may, ultimately, affect grain yield. This study aimed to establish a sowing window for irrigated maize crop, based on simulation results obtained with the decision support model CSM-CERES-Maize. Simulations were made for crop management conditions of Riacho´s Farm, located in Matozinhos, Minas Gerais State, Brazil. It was employed the model´s seasonal tool, along with a data set containing 46 years of weather data records, to simulate maize yield for weekly sowing scenarios, starting on August 1 st and ending on July 24 th of each year. One defined an irrigated maize sowing window, taking into account the yield break risk that a farmer would be willing to take. The model proved to be an interesting tool to assist in decision making, regarding crop and irrigation management, for an irrigated maize production system. Assuming a 10% yield break in the expected average maximum maize yield, it was defined as sowing window, the period from January 23 rd to March 6 th , with February 20 th as the best sowing date. Other sowing windows may be established according to the risk that the farmer would be willing to take.