Calendário agroclimático para a cultura do milho na região de Arapiraca-AL

Abstract

The variability of total annual precipitation of rain and its distribution during the rainy season in the region of Arapiraca, explains most of the fluctuations in crop yield, which occurs in different years and locations. However, regional water conditions for agriculture must also be considered taking into account the storage capacity of water form the soil. Water is essential to productivity of crops and their consumption is determined by water evaporative demand of the atmosphere, soil type and plants characteristics. A good distribution of rainfall regulates water factor of production, preventing soil moisture is reduced to levels that condition the plant water stress. In particular, the corn grown in the irrigation system in this region has the yield highly dependent on interactions between their phenological phases and water availability which is determined by the storage of water from the soil and the irregularity of the rainfall regime. This work aimed to analyze the sowing dates of maize which have lower risk of water stress during sowing until 10 days after flowering in the region of Arapiraca. For this, calculations were made of daily water balance for two soil types, representing the region of cultivation of maize, with precipitation data of a 37 years period, from the meteorological station of old Empresa de Pesquisa do Estado de Alagoas - EPEAL and the Secretaria Municipal de Arapiraca - SEMAG, considering the life cycle of maize cultivar BR 106 of Empresa Brasileira de Pesquisa Agropecuária -EMBRAPA, sown in the period March to August. Also was calculated the accumulated degree-days (GDA) for maize in the sowing- flowering period to estimate dates of flowering for the different simulated sowing dates. Through an analysis of the frequency distribution of the satisfaction water indices of culture (ISH), obtained from daily water balance, it is calculated the probability of this index is above 0.5 with probabilities exceeding 80% in time of sowing and the critical phase of requirement of water by maize (10 days before flowering and 10 days later). The results allowed the determination of planting calendar for maize in the region of Arapiraca - AL starting on 01 June and ending on June 30 for the two soil types studied.