Nitrate Removal in Saturated Riparian Buffers: A Result of Denitrification?.

Nitrate leaching from the Midwestern Corn Belt is a major environmental concern. The majority of this leaching is centered on the tile drained portion of the Corn Belt. In this region, tiles export nitrate to adjacent river systems that eventually drain to the Gulf of Mexico, where hypoxia is an issue. Methods for removing nitrate from tile drainage water include both in-field and edge-of-field practices. This research focused on saturated buffers, a newer edge-of-field practice. Saturated buffers are riparian buffer strips that are saturated with tile drainage water via an Agri Drain control box and shallow subterranean tile that runs parallel to the edge of the field. The tile water that seeps through the buffer zone contacts the upper soil horizons rich in organic matter, which provides the potential for denitrification to occur. With this research, we measured denitrification with the acetylene inhibition core method. This method was done for two saturated buffers in north-central Iowa, one planted in switchgrass (Panicum virgatum L.) and the other planted in switchgrass, silver maple (Acer saccharinum L.), common ninebark (Physicarpus opulifolius L.), and nanny berry viburnum (Viburnum lentago L.). The saturated buffers have removed about 50% of the total tile nitrate load per year. Our hypothesis was that the majority of this nitrate is removed through denitrification.