By following a few simple recommendations, farmers who apply manure to no-till fields can decrease the chance that pathogens end up in runoff and pose environmental and health hazards.
Ohio State University scientists with the Ohio Agricultural Research and Development Center studied the transport of Cryptosporidium, a parasite present in animal waste, through no-till and tilled fields. They found that a greater amount of the parasite moved along with excess water through no-till fields and into tile drains than in tilled fields, especially during a rain event.
Cryptosporidiosis, caused by Cryptosporidium, is a waterborne disease causing intestinal illness in humans.
Warren Dick, an OARDC soil microbiologist, said that Cryptosporidium moves more readily through no-till fields because of the presence of macropores created by either earthworms or plant roots.
“We found that the macropores extend from the soil surface right down to the tile drains so the parasite has a conduit from the manure directly to a water source,” Dick says.
He and his colleagues took the study one step further to look for ways to keep Cryptosporidium in the soil and found that some tillage seems to do the trick.
Researchers treated six undisturbed no-till and six no-till blocks that were tilled on the surface with liquid manure containing Cryptosporidium oocysts to test the effect of tillage and rainfall on parasite transport.
“Even before any artificial rain was applied, almost 30% of the liquid manure moved through the no-till soil, but none moved through the tilled blocks,” Dick says. “During the rain event, a greater number of Cryptosporidium moved through the no-till blocks compared to the tilled blocks.”
However, the number of oocysts recovered from the tilled blocks was greater than from the no-till blocks, researchers found.
“If no-till growers can do just a little light tillage right over the drain tiles, it can have a tremendous impact on the movement of pathogens and nutrients from the soil surface to the field drain tiles, with potential decreases in the transport of oocysts up to 80%,” Dick says. “Tilling disturbs the macropores and disrupts the direct linkage from the soil surface to the drain tiles.”
In addition to tillage, other factors impacting the transport of Cryptosporidium include rainfall timing and rainfall intensity. To lessen the impact, researchers recommend that farmers apply manure at least 48 hours prior to an anticipated rainfall event.
“This study is in no way advocating that no-till is a bad management practice. As a whole, no-till has a multitude of environmental and crop production benefits,” Dick says. “But any production practice can be improved upon, and this study demonstrates that there are ways of making no-till better, for people and for the environment.”
The study, “Effect of Tillage and Rainfall on Transport of Manure-Applied Cryptosporidium parvum Oocysts Through Soil,” was recently published in the Journal of Environmental Quality. It's one of the few studies available demonstrating the transport of manure pathogens through no-till soils.
Fertilizer chemicals and nutrients are also readily transported through no-till soils via macropores from the surface to drain tiles. The results from this study suggest that tilling directly over the drain tile lines could produce similar results in reducing movement of these materials from the field.
Dick and his colleagues are also studying the transport of E. coli and Campylobacter through no-till soils. Both cause foodborne illnesses.