An Ohio State University (OSU) study shows a little light tillage over drain tiles in no-till fields can help impact the movement of pathogens and nutrients from the soil surface to the drain tiles and into runoff water. OSU scientists studied the transport of Cryptosporidium, a parasite present in animal waste, through both no-till and tilled fields. They found a greater amount of the parasites moved along with excess water through no-till fields and into tile drains than in tilled fields, especially during a rain event.

According to Warren Dick, OSU soil microbiologist, 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 found that some tillage seems to keep Cryptosporidium in the soil.

Researchers tested both undisturbed no-till plots and no-till plots that had been tilled on the surface, applying liquid manure containing Cryptosporidium oocytes to both types of plots. “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 (soil) blocks,” Dick says. “During the rain event, a greater number of Cryptosporidium moved through the no-till blocks compared to the tilled blocks.”

The researchers say even light tillage over the drain tiles has a tremendous impact on the movement of pathogens and nutrients, with the potential to decrease the transport of oocytes by up to 80%. Tilling disturbs the macropores and disrupts the direct link from the soil surface to the drain tiles.

Rainfall timing and intensity also play a role in transporting Cryptosporidium. The researchers recommend producers 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. But, any production practice can be improved upon and this study demonstrates that there are ways of making no-till better for both people and the environment,” Dick says. The study was recently published in the Journal of Environmental Quality.