Cultivo do milho: zoneamento agrícola.

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Época de plantio de sorgo.

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Balanco hídrico num latossolo vermelho escuro álico cultivado com milho com irrigação por aspersão.

The water balance components were determined for cerrado soil planted with corn (Zea mays L.) under sprinkler irrigation conditions. A neutron probe was used to determine the soil moisture profile, which was then used, in association with soil water potential, to estimate deep percolation and evapotranspiration fluxes. The method used to estimate deep percolation and evapotranspiration fluxes proved to be reliable for soil water stress condition and unreliable for rainy day condition, when water storage increased in the soil profile. The upward movement of soil water was the major source of water supply for corn growth, mainly after a shortage of water in the soil profile. Deep percolation represented up to 67% of total water loss (Through drainage and evapotranspiration). The averages for evapotranspiration fluxes, with no water stress condition, were: 1,94mm day -1, for 42 through 60 days after planting; increasing to 5,19mm day -1, during 60 through 84 days after planting, raching a maximum of 5,96 mm day -1, during 84 through 108 days after planting; and decreasing to 4,25mm day -1, during 108 through 115 days after planting

Fatores ambientais que afetam a taxa se secagem no grão de milho (Zea mays L.) após a maturidade fisiológica.

Avaliou-se a influencia dos fatores ambientais na perda de agua pelo grao de milho (Zea mays L.), apos a maturidade fisiologica, em duas safras (1995/96 e 1997/98), em Botucatu, SP. O delineamento experimental utilizado foi o de blocos casualizados, com cinco e quatro repeticoes, nas respectivas safras. A avaliacao da perda de agua do grao, em nove cultivares (AG 122, AG 1051, AG 9012, AG 8012, C 901, XL 370, Z 8392, Z 8452 e Z 8501), iniciou-se apos todas as cultivares terem atingido a maturidade fisiologica. Posteriormente, a perda de agua pelos graos foi correlacionada com as medias dos elementos meteorologicos no periodo amostrado. Os resultados indicaram que graus-dia, radiacao solar global, insolacao e evaporacao do tanque classe A foram os elementos que mais se relacionaram com a perda de agua nos graos, com efeito quadratico e que ate aproximadamente 16% de teor de agua no grao estes fatores apresentaram efeito bem marcante

Utilização do modelo Ceres-Maize na avaliação de estratégias de irrigação na cultura do milho em duas regiões do Estado de Minas Gerais.

The Ceres-Maize model was to study water consumption and profitability of maize crop at three growing seasons, for two regions of Minas Gerais, Brazil, for establishing and evaluating the necessary database for the use of this model. Cultivar BR201 was used to evaluate conduction distinct strategies of the crop, at the location of Sete Lagoas and Janauba. Treatments consisted of conduction of irrigated and non-irrigated crops during the growing seasons (15 May to 15 October and 15 December) and two frequency levels of water application: high (central pivot) and medium (conventional sprinkler irrigation). The simulation results have shown that the use of these models as complementary tools to conventional trials and the information presented helped on building the necessary files for simulations. It was observed that although irrigation allows higher yield, its influence on the costs of maize production resulted in a negative economic feedback for both location studied, except for the 10/15 and 12/15 negative season in Sete Lagoas under medium frequency irrigation conditions. Yields irrigated green maize despite the high production costs, showed more profitability when compared to grain production, being economically viable in the majority of treatments.