#02-095

Complete

Date Full Report Received

05/28/2003

Date Abstract Report Received

05/28/2003

Investigation

Institution:
Primary Investigator:

Land application of swine manure on tile-drained soils has become a controversial issue in some swine producing areas because of uncertainties regarding the leaching of nitrates, phosphorus, and pathogens through the soil and into tile drainage water. A study was started on a set of tile drainage plots at Waseca, MN in November 2001 when liquid swine manure spiked with Salmonella anatum was sweep-injected into three plots at a rate of 5000 gal./acre. Urea was applied to three additional plots in April 2002. Corn was grown and samples of soil and tile water were taken during the year. Corn grain yields were excellent and were not different between the manure and urea N sources. Nitrate-N levels in the tile water and in the soil samples during and at the end of the season were lower for the manure treatment compared with urea even though 150 lb per acre more “available” N had been applied in the manure treatment. These findings suggest denitrification losses of N from the fall-applied manure may have been substantial in June when excess precipitation (7.15”) occurred and soils became saturated. Soil test phosphorus (P) analysis showed no detectable movement of P from the manure down through the soil profile. Detectable levels of total P were found in 89% of the water samples, whereas only 47% of the samples contained detectable levels of soluble P. Losses of soluble and total P were very small and did not appear to be different for manure vs. urea. Salmonella anatum was not found in any of the water samples, indicating either the organism did not survive the winter or it was retained in the upper soil profile and not transported to tile drainage water. Numbers of fecal coliforms were similar for both manure and urea treated plots. This suggests these organisms did not survive over winter in the added manure and that levels found during the six-week drainage period were probably background levels.