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TECHNICAL REPORTS

Vadose Zone Processes and Chemical Transport

Effect of Tillage and Rainfall on Transport of Manure-Applied Cryptosporidium parvum Oocysts Through Soil

^a Food Animal Health Research Program, The Ohio State Univ., Wooster, OH 44691
^b School of Environment and Natural Resources, The Ohio State Univ., Wooster, OH 44691
^c USDA-ARS, Coshocton, OH 43812
^d National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
^e Veterinary Population Medicine Dep., Center for Animal Health and Food Safety, Univ. of Minnesota, St. Paul, MN 55108. Note: The first and second author contributed their expertise and time to this paper equally. Research was performed at The Ohio State University-The Ohio Agricultural Research and Development Center, Wooster, OH 44691

^* Corresponding author (dick.5{at}osu.edu).

Received for publication September 30, 2008. Most waterborne outbreaks of cryptosporidiosis have been attributed to agricultural sources due to the high prevalence of Cryptosporidium oocysts in animal wastes and manure spreading on farmlands. No-till, an effective conservation practice, often results in soil having higher water infiltration and percolation rates than conventional tillage. We treated six undisturbed no-till and six tilled soil blocks (30 by 30 by 30 cm) with 1 L liquid dairy manure containing 10⁵ C. parvum oocysts per milliliter to test the effect of tillage and rainfall on oocyst transport. The blocks were subjected to rainfall treatments consisting of 5 mm or 30 mm in 30 min. Leachate was collected from the base of the blocks in 35-mL increments using a 64-cell grid lysimeter. Even before any rain was applied, approximately 300 mL of water from the liquid manure (30% of that applied) was transported through the no-till soil, but none through the tilled blocks. After rain was applied, a greater number and percentage of first leachate samples from the no-till soil blocks compared to the tilled blocks tested positive for Cryptosporidium oocysts. In contrast to leachate, greater numbers of oocysts were recovered from the tilled soil, itself, than from the no-till soil. Although tillage was the most important factor affecting oocyst transport, rainfall timing and intensity were also important. To minimize transport of Cryptosporidium in no-till fields, manure should be applied at least 48 h before heavy rainfall is anticipated or methods of disrupting the direct linkage of surface soil to drains, via macropores, need to be used.