Predicting the effects of drainage systems on corn yields

Abstract

Stress day index (SDI) models were incorporated in the water management simulation model, DRAINMOD, to quantify the effect of soil water stresses on corn yields. The effects of a combination of excessive and deficient soil water conditions were approximated by a simple first-order crop response model, YR = YRw × YRd, where YR is the overall relative yield, and YRw and YRd are the relative yields due to excessive and deficient soil water conditions, respectively. The accuracy of the modified water management model was evaluated by comparing predicted and measured corn yields for 16 plot years of experimental data on the Tidewater Research Station near Plymouth, NC. The predicted and measured results were in good agreement with the model describing 63% of the variation in yields for the 12-year period. Use of the modified water management model was demonstrated by simulating the performance of several drainage system designs for a Portsmouth sandy loam soil. The results of the simulation show that a maximum long-term relative yield of 80% of the potential corn yield can be obtained with a drain spacing of 40 m or less with good surface drainage. Higher yields could not be obtained without irrigation to reduce deficit soil water conditions. The response of long-term average corn yields to surface drainage varies inversely with the intensity of subsurface drainage. The 25-year average yield for 100 m spacing was only 47% of the potential yield when the surface drainage was poor as compared to 61% of potential yield for good surface drainage.