The impact of irrigation scheduling on aflatoxin risk for peanuts using the CSM-CROPGRO-Peanut model

Abstract

Aflatoxin contamination in peanuts poses an ongoing threat to production and economic value in the United States. Irrigation is a management intervention established for mitigating preharvest aflatoxin levels, but its effect across specific conditions has not been clearly documented. This study used the CSM-CROPGRO-Peanut model of DSSAT with an aflatoxin module to evaluate soil series and irrigation strategies across 12 peanut-producing counties in Georgia. Simulations included five soil series, ten irrigation strategies, four planting dates, twelve counties and eight production years from 2016 to 2023, totaling 19,200 runs. Irrigation strategies had the largest effect on simulated aflatoxin concentration. Regional-scale evaluation against county-year FSIS observations showed limited agreement, with NSE values of −0.16 for the mean series and −0.66 for the median series. Elevated simulated aflatoxin concentrations were associated with weekly water inputs below the Extension crop-water requirement during pod development. Irrigation triggered when 50% of the available water capacity remained (IT50) reduced mean simulated aflatoxin concentration to less than 0.01 ppb, compared with 57.8 ppb under rainfed conditions. Soil series differed in simulated aflatoxin response, particularly under rainfed and low-irrigation conditions, but these differences were not explained by cumulative available water capacity alone. The analysis was limited by station-based weather inputs and the lack of field-level management information in the observed FSIS data, which restricted evaluation of the model under individual field conditions.