SIMULATION OF EVAPOTRANSPIRATION FROM GROUNDNUT UNDER WET AND DRY CONDITIONS

A diffusion based simulation model was tested on groundnut (Arachis Hy pogaea L) in a lateritic sandy loam soil (Oxic-Haplustalf) of eastern India. Two moisture regimes, wet and dry, were induced by recharging t he soil profile (1.2 m depth) to field capacity storage, whenever soil water pressure reached -0.078 m at 0.225 m (wet) and 0.6 m (dry) soil depths, respectively. Moisture retention characteristics and hydrauli c conductivity curves were measured for three distinct soil layers of the experimental soil profile. Readily available meteorological, soil and plant data were used as input parameters of the model. The simulat ed cumulative ET (ET(s)) closely corresponded with the field observed cumulative ET (ET(f)) in the early part of the drying cycle following irrigation. However at the later part of the drying cycle ET(s) deviat ed from the ET(f), this being particularly true under wet regime. The closest match between ET(s) and ET(f) was observed under dry soil wate r regime 50-70 days after sowing (DAS). The model underestimated the f ield observed ET up to 50 DAS and there after overestimated it.