Cropping System and Type of Pig Manure Affect Nitrate-Nitrogen Leaching in a Sandy Loam Soil.

The application of livestock manure can result in the loss of nitrate-nitrogen (NO-N) and degrade surface and groundwater. A 3-yr lysimeter study was set up to compare the effect of cropping system and nitrogen (N)- and phosphorus (P)-based pig manure application rates on the loss of water and NO-N below the root zone. The experiment was a split-plot design with annual and perennial cropping systems as the main factor. Five nutrient management treatments were the subplots: N-based liquid pig manure application; P-based liquid pig manure application, N-based solid pig manure application, P-based solid pig manure application, and a control without amendment. The results showed that 40 to 60 kg NO-N ha was lost from the annual plots in 2010 and 23 to 60 kg NO-N ha in 2011, whereas a negligible amount of NO-N was lost from the perennial (<1 kg ha) plots in both years. The application of solid pig manure on a P basis followed by urea in subsequent years reduced the risk of NO-N leaching over the course of the rotation, likely due to immobilization of N by the straw in the solid pig manure. Our study showed that a perennial cropping system consisting of a mixture of grasses has the capacity to receive and utilize significant amounts of nutrients with negligible amount of nutrient leakages to the adjacent environment. The inclusion of grasses in a crop rotation and their use to take up excess nutrients are sustainable practices that will benefit the environment.