The study of water balance components is essential to understand the dynamics of soil water, providing subsidies to agricultural management and optimization of water use. The objective of this study was to determine the water balance components in a soil cultivated with castor bean under rainfed conditions. An experiment was installed in a 4 ha area in the Centro de Ciências Agrárias, UFPB, in the municipality of Areia, Paraiba state (6o 58' S, 35o 41' W e 620 m), a rain gauge and three plots contained an access tube for neutron probe measurements, up to the depth of 1.60 m, and a set of eight tensiometers at depths of 0.10, 0.20, 0.30, 0.40, 0.60, 0.80, 1.20 and 1.60 m. Infiltration tests were performed on soil surface and 0.20, 0.40, 0.60 and 0.80 m depth for the determination of the saturated hydraulic conductivity of soil. It was verified that the evapotranspiration of castor bean followed the variations of rainfall with the mean and total values of 2.43 mm d-1 and 342.5 mm, respectively. The variation of soil moisture storage change followed the variations in rainfall and the flux of water crossing the last soil layer (capillarity rise or drainage) had very small values.
Ricinus communis L.; evapotranspiration; drainage; soil water content
