Evaluation of cropgro-dry Bean and Checkpea models in a semi-arid environment.

Crop yield is a result of complex interactions among soil, crop, weather and agricultural practices for which experimentation on each possible combination is impossible. The potential use of models is more demanding in the dry areas of sub-Saharan Africa than any other region. These areas are where unpredictable fluctuation of weather and climate has made many field experiments a futile exercise. Potential modes, however, should be validated under the specific environments before they are adapted to solve practical problems. Therefore, the objective of this study was to validate the CRPGRO grain legume models of DSSAT is a semi-arid environment of Ethiopia using field experiment data collected for bean and chickpea under well-watered and water-deficit conditions. The CROPGRO model simulated leaf area index (LAI), crop evapotranspiration (ET) and above-ground biomass (AGB) at harvest with reasonable accuracy while the simulation for grain (GY) at harvest was very good for both bean and chickpea. The models showed good performance in simulating these variables under both well-watered and water-deficit conditions during the reproductive period of the crops. However, the simulation of yield components (weight per seed, number of seeds per m2, number of seeds per pod) at harvest in both seasons, and biomass accumulation during crop cycle under high temperature conditions was very poor in both crops suggesting the need for further improvement of the models to suit the study environment. Model weakness was also observed on simulation of maturity date in bean and flowering date in chickpea. It it concluded that with further minor calibration, the model has good potential to be used as a decision support tool in the semi-arid areas of Ethiopia where long-term field experiment is costly and less effective as a result of fluctuating weather conditions.