Simulation of corn yield by a water management model for a Coastal Plain soil in Virginia

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 three years. Water table elevations predicted by the model were in good agreement with measured water table elevation data with an average deviation of 9.47 cm for the three years of record. The YIELD version of DRAINMOD was used to predict corn yield for the subirrigation/controlled drainage site. Average corn yield predictions by the model agreed reasonably well with the observed average corn yield data with relative errors of 19.2, 4.4, and 8.1 percent 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 results indicate that DRAINMOD is a powerful tool for the design and evaluation of subirrigation/controlled drainage practices in the Virginia Coastal Plain.

Simulations 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 21.3 m, a drain depth of 110 cm, and a 65 cm 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.