SUBSURFACE DRAINAGE AND LIQUID MANURE

Authors: HOORMAN, J - OSU-EXTENSION AGENT; Shipitalo, Martin

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2005
Publication Date: 7/1/2006
Citation: Hoorman, J.J., Shipitalo, M.J. 2006. Subsurface drainage and liquid manure. Journal of Soil and Water Conservation. 61(3):94A-97A.

Interpretive Summary: Land application of liquid animal wastes is a recommended Best Management Practice (BMP) that can effectively utilize the nutrients and organic matter contained in these materials for crop growth. In some instances, however, when these materials are applied to soil with subsurface drainage systems it can contaminate the water that emerges from the drains. This can result in fish kills in streams and large fines levied on the farmer. We examined the official records of these incidents in Ohio to determine the magnitude of the problem and the factors that contributed to these incidents. The results indicate that the problem is widespread in Ohio and is likely to occur in throughout the US Midwest where soil, climatic, and farming practices are similar. In 75% of incidents mismanagement was a contributing factor, which suggests that farmers can reduce the number and severity of incidents by improving their attention to factors that they can control. Although tillage can reduce movement of the liquid wastes to drains it was not effective in all instances. Plugging the drains to keep the wastes from entering the streams and ditches fail 50% of the time and should not be relied upon.

Technical Abstract: Although land application of liquid animal wastes is a widely used BMP, in fields with subsurface drainage it can result in rapid movement to drains and offsite. In the 4 year period, 2000 to 2003, ninety eight incidents where agricultural wastes in drainage waters contaminated streams were recorded by authorities in Ohio. We investigated these reports to determine the factors that contributed to these incidents and to determine possible management options for reducing their occurrence. Violations occurred most frequently with liquid swine or dairy wastes and occurred with all methods of application irrigation, surface spreading, and subsurface injection. In most instances multiple factors contributed to each incident. The factor most commonly cited (41 cases) was application to saturated soils or heavy rainfall after application. Thus, avoiding these conditions should reduce the number and severity of incidents. While disruption of soil macropores with tillage may reduce movement of wastes to drains, 17% of the incidents occurred on soils that were tilled or wastes were incorporated. Drain line plugs failed 50% of the time they were used.