Fate of Salmonella following application of swine manure to tile-drained clay loam soil.

Land application of animal manure is an important means of utilization of nitrogen and phosphorus. However, the presence of pathogens in manure and their occasional leaching into subsurface water has become a topic of concern during the past few years. This study was undertaken to determine the extent to which Salmonella anatum may leach through tile-drained clay loam soil on which swine manure has been applied. For this purpose, swine manure was experimentally contaminated with S. anatum and applied to three tile-drained plots in winter of 2001 while another three plots served as negative controls. Following rainfall events in the spring of 2002 the tiles started to flow and leachate samples of subsurface water were collected at various time intervals and tested for S. anatum. Salmonella anatum was not found to leach into the subsurface drainage water indicating that it was either retained in the upper layers of soil or did not survive over winter. The leaching of faecal coliforms and coliphages was also tested. Faecal coliforms and coliphages were detected in the subsurface water from both manure and control plots, indicating the ability of the tile drainage system to transport these organisms to groundwater as the water percolates through the soil. Additional temporal studies over a longer time period are needed to determine the survival and leaching of pathogens and indicators into subsurface water.