Consumo hídrico da soja no nordeste paraense.

Abstract

Several studies conducted in Brazil have shown that crop yield is affected by different climatic factors, including water stress. Water consumption of soybean varies with plant development and environmental conditions, with significant impacts on its yield when this demand is not met. Water consumption of soybean crop (Glycine Max (L.) Merryl) grown during the 2007 crop cycle in a soybean production areas in the Amazon was investigated. The soybean water consumption followed the trend of increase in LAI, with maximum evapotranspiration during grain filling period, whose mean value was 4.1±0.4 mm.day-1. Low values of the decoupling factor during the initial phase of the crop indicated a considerable contribution of soil evaporation and a higher stomatal control of the process. After the canopy closure there was a decrease in stomatal control indicating an increment in the transpiration contribution besides a canopy decoupling with the atmosphere, which indicated a direct control of evapotranspiration by the available energy. Slight reductions in soil water content during the reproductive phase suggested a certain importance of stomatal control in soybean evapotranspiration. The total water consumption of soybean from the V1 stage until harvest was 335 mm.