Simulation of Corn Yield by a Water Management Model for a Coastal Plain Soil in Virginia

Abstract

ABSTRACT DRAINMOD, a water management simulation model for artificially-drained soils, was evaluated for a Virginia Coastal Plain soil by comparing predicted and measured water table depths from a subirrigation/controlled-drainage site over a period of 3 years. Water table evaluations predicted by the model were in good agreement with measured water table elevations, with an average deviation of 9.47 cm for the 3 years of record. The YIELD version of DRAINMOD was used to predict relative corn yield for the subirrigation/controlled-drainage site. Average corn yield predictions by the model agreed reaonably well with the observed average corn yield, with relative errors of 19.2, 4.4, and 8.1% for 1984, 1985, and 1986, respectively. Additionally, corn yields predicted for a conventional drainage system were considerably lower than those predicted for subirrigation/controlled-drainage, reaffirming the need for irrigation of corn in the Coastal Plain region of Virginia. Research indicate that DRAINMOD is a powerful tool for the design and evaluation of subirrigation/controlled-drainage practices in the Virginia Coastal Plain. Simualations were performed for a 20-year period to determine the effects of system design on corn yield. An economic analysis was performed to determine optimal system design for maximizing profits from corn production. A drain spacing of 21.30 m, a drain depth of 1.10 m, and a 0.65 m weir depth were the design parameters recommended as optimal for maximizing profits from subirrigation/controlled-drainage of corn on a Myatt fine sandy loam soil in the Virginia Coastal Plain.