Simulation of defoliation in peanut from soil water stress

The peanut growth and development model, PEANUT, was modified to enable prediction of defoliation resulting from soil water stress. Defoliation was measured during the 1988 growing season at Lewiston, NC, and soil water stress was predicted with PEANUT for the same period. A regression equation relating soil water stress to percent defoliation was developed and incorporated into PEANUT. The modified PEANUT model predicted percent defoliation and total leaf mass for 1988 in good agreement with the observed data. Total leaf masses predicted from the original and modified PEANUT model were compared to observed data for 1976, 1977, 1978, and 1982. The total leaf masses predicted by the modified PEANUT were in good agreement with the observed data for all years except 1978. Limited data were available to develop the regression equation used in the modification, so its applicability may be restricted.