Adapting and evaluating the CROPGRO-peanut model for response to phosphorus on a sandy-loam soil under semi-arid tropical conditions

is an important legume crop worldwide, occupying 26 million hectares of planted area with an annual production of about 35 million tons. Developing countries account for 97% of the world peanut area and about 94% of total production. Phosphorus (P) is an essential macronutrient for peanut growth and development, and its availability is often limiting to crop growth under many soil conditions. Crop simulation models can provide an alternative, less time-consuming and inexpensive means of determining the optimum crop P requirements under varied soil and climatic conditions. The CROPGRO-peanut model is capable of simulating the growth and yield of peanut in response to weather, soil, water, nitrogen, and management practices. However, its capability in predicting crop responses to soil and fertilizer P needs to be established. The objective of this study was to adapt and evaluate the CROPGRO-peanut model within the DSSAT system to simulate the growth and yield of peanut in response to soil and fertilizer P. Data from four P fertilizer treatments (0, 13, 26, and 39 kg P ha-1) and two cropping seasons (2002 and 2003) experiments on an Alfisol were used to calibrate the model. The model was tested using two data sets from a P fertilizer × cultivar trial conducted on-station in 1997 and 1998 and P fertilizer × fungicide trials on-farm in 2002. The results showed that the P module accurately simulated the seasonal patterns of aboveground biomass and pod yield in the on-farm trials. Averaged across sampling dates, RMSEs in the on-farm trials ranged from 100 to 398 kg ha-1 (d ≥ 0.99) for total biomass and from 97 to 263 kg ha-1 (d values ≥ 0.98) for pod yield. At final harvest, the variability of simulated biomass and pod yield was about 5.4 and 10.0% of the observed biomass and pod yield, respectively. The model simulated the seasonal patterns of vegetative P content in the four farmers' fields fairly well, with RMSEs ranging from 0.28 to 1.29 kg ha-1 when averaged across measurements dates. The model outputs were sensitive to soil P test values, the method of P fertilizer application, and to plant P uptake factors, such as root P extraction radius and root length density. Increasing or decreasing the optimum P concentration of seed and minimum P concentrations of leaf and stem had the greatest effects on pod yield compared to other plant parts. The generic soil and plant P model in DSSAT 4.5 is capable of simulating peanut growth and yield in response to soil P levels or fertilizer application on an Alfisol. The model can be used to evaluate the effects of P fertilizer application on peanut growth and yield under different soil and climatic conditions. The model can also be used to develop fertilizer recommendations for peanut production in different regions.