Water balance in soil cultivated with cowpea

Abstract

The water balance components (evapotranspiration, variation of the water storage in the soil, deep drainage, capillary rise, rainfall), were determined for an Oxisoil cultivated with cowpea (Vigna unguiculata (L.) Walp.). An automated rainfall gauge and three plots were installed in an area of 4 ha in the CCA/UFPB, Areia-PB (latitude 6^o58’12" S, longitude 35^o42’15" W, altitude: 620 m). Each plot consisted of an access tube for neutron probe measurements and a set of eight tensiometers. Infiltration tests were performed for the determination of the saturated soil hydraulic conductivity. It was verified that the deep drainage was underestimated, due to the small value (-17.23 mm) found for that soil type. The variation of water storage in the soil followed the variations in rainfall. The evapotranspiration was higher in the periods of increased water availability, with the average value of 4.12 mm d^-1, and the greater water consumption occurred in the reproductive phase.