Comparative evaluation of three-crop growth models for the simulation of soil water balance in oilseed Brassica

Performance of three-crop growth models for dynamic simulation of soil wate r balance in the sandyloam soils cropped to oilseed Brassica was evaluated. The model parameters were subjected to sensitivity analysis, modified and calibrated for local environment and verified with experimental field value s. Simulated root zone (0-120 cm) moisture from Campbell-Diaz model was mor e sensitive to stepwise changes in input parameters as compared to the O'Le ary and SWASIM models. While calibrating these models during post-rainy sea son of 1992-1993, simulated profile moisture from the Campbell-Diaz and SWA SIM models, on an average, did not deviate by more than +/- 5% from measure ments except on one or two occasions whereas the O'Leary model gave slight overestimates up to seed filling stage and underestimates of the order of - 6% in the post-seed filling stage. Campbell-Diaz model requiring least numb er of inputs yielded the lowest error estimates (6.01-11.06 mm) followed by the SWASIM (6.46-18.88 mm) and O'Leary (8.3-20.6 mm) models. The Campbell- Diaz and SWASIM models can also be successfully used with common coefficien ts and also to simulate layerwise soil moisture contents, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.