Evaluation and application of the CROPGRO–Soybean simulation model in a Vertic Inceptisol

Crop simulation models are valuable research tools in agricultural decision making. In order to increase its general applicability, models need to be evaluated in diverse conditions. To achieve this, CROPGRO–Soybean model was evaluated on Vertic Inceptisols in a climatically variable semi-arid tropical condition. The model predicted reasonably the temporal changes in leaf area index, biomass and grain yield. The model was used to develop yield–evapotranspiration (ET) relationship, and to assess the influence of soil water-storage capacity on yield. Yield was linearly related to ET and was reduced non-linearly as soil depth decreased. The yield reduction was minimal when depth decreased from 90 to 67 cm but severe reduction occurred when depth decreased below 45 cm. There exists a threshold soil depth (37 cm), below which crop productivity in Vertic Inceptisols cannot be sustained, even in good rainfall years. There is an urgent need to develop sustainable natural resource management technology to prevent further degradation of Vertic Inceptisol. CROPGRO–Soybean model can be successfully used as a research tool to evaluate the risks associated in adapting such technologies.