#03-094

Complete

Date Full Report Received

06/15/2004

Date Abstract Report Received

06/15/2004

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 continued on a set of tile drainage plots at Waseca, MN in November 2002 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 2003. Corn was grown and samples of soil and tile water were taken during the year. Corn grain yields were excellent given the dry conditions (April-September growing season rainfall was 7.8” below normal) and were not different between the manure and urea N sources. Nitrate-N concentrations in the tile water were slightly higher for the urea treated plots (13.2 mg/L) compared to the manured plots (11.3 mg/L) but nitrate-N losses were not different between the two N sources (10 to 11 lb/A). These nitrate-N concentrations and losses are likely due to the residual effects of 2002 and before and not to the 2003 treatments in this drier-than-normal year. Detectable levels of total P and soluble ortho-P were found in 84 and 81% of the water samples, respectively, but were not different between the two N sources. Detectable levels of total P ranged from 0.02 to 0.09 mg/L while soluble P concentrations ranged from 0.01 to 0.05 mg/L for all 42 samples with no difference between urea and manure-treated plots. 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 seven-week drainage period were probably background levels. For further information contact Dr. Gyles Randall at (507) 837-5616 or grandall@umn.edu.