Effects of Subsurface Drain Depth on Nitrogen Losses From Drained Lands

A simulation study was conducted to determine effects of drain depth on nitrogen (N) loss in drainage water.Simulations were conducted for drain depths of 0.75, 1.0, 1.25, and 1.5 m for a Portsmouth sandy loam at Plymouth, NorthCarolina. A wide range of drain spacing was considered for each depth. Corn yields were predicted and an economic analysiswas conducted to determine the drain spacing giving maximum predicted profit for each depth. Results showed that nitrogenlosses from subsurface drains can be reduced by placing the drains at shallow depths. In order to satisfy agriculturalproduction requirements, shallow drains must be placed closer together than deeper drains. While predicted agriculturalprofits for the shallow drains are reduced somewhat compared to the deeper drains, overall profits are substantially increasedwhen the cost of removing N from drainage water is considered.