1997 Annual Report for FS97-051
Effect of Different Application Rates of Swine Lagoon Effluent on Corn and Wheat
Summary
In recent years there has been a great deal of concern over the application of swine lagoon effluent to fields which results in high concentrations of phosphorus, copper and zinc in the soil. The rates at which swine waste must be applied in order to provide sufficient nitrogen to the crop results in high soil levels of phosphorus, copper and zinc which can have negative effects on soil and water quality. The excess elements have become a problem because the crop can’t take up all that is applied during the year and the excess runs off into rivers and streams or stays in the soil approaching toxic levels.
The majority of swine producers in North Carolina apply swine lagoon effluent to fields of grass to be used for grazing cattle or producing hay. It was John Hart’s belief that the nutrients in the effluent can be better utilized to fertilize grain crops grown in rotation.
For this SSARE Producer Grant project, three five-acre plots 250 feet wide and 875 feet long were laid out in a field adjacent to the swine operation. One plot received swine lagoon effluent at current recommended rates providing sufficient nitrogen for optimal production. The second plot received the effluent at a rate that provided adequate phosphorus for optimal production. The third plot received no effluent but instead received commercial fertilizers with nitrogen and phosphorus at optimal rates.
Corn, soybeans and wheat were grown on the plots during the three years of the project. Optimal effluent application rates were based on the recommended needs of the crop being grown during the application cycle. Soil samples were taken before and throughout the project to determine the quantity of applied nutrients remaining in the soil after harvest. Tissue samples and yield data were taken to determine the quantity of nutrients removed from the plots by the three crops. Soil and waste analysis was conducted by the North Carolina Department of Agriculture. Cost data were recorded to determine which treatment was most cost effective.
The producer concluded that swine effluent should be applied at the rate that provided adequate phosphorus for optimal production in order to avoid over applying phosphorus. The producer also suggested adding microbial phytase to the animal’s diet to reduce the amount of phosphorus in the lagoon effluent. Another suggestion stemming from this project is to separate the solids from the effluent prior to running the effluent into the lagoon. This would however require additional handling and transport.