Nutrient Management, Cover Crops, and Drainage Water Management for Reducing Nitrate-N Losses in Iowa.

With the release of the Iowa Nutrient Reduction Strategy in 2013, there has been an increased emphasis on practices that can be used to reduce field to stream nitrate-N loss. Three important in-field practices for reducing nitrate-N export are nutrient management, cover crops, and drainage water management. We have been monitoring impacts of nutrient management practices for 25 years at a site in north-central Iowa. From this study, we have found that nitrate loss is more influenced by land use, but nutrient management is an important factor to consider in a systems approach for reducing nitrate-N loss. From over 10 years of research work in north-central Iowa, we have found that the use of a winter cereal rye cover crop reduces nitrate-N concentration in tile drainage by about 25%. This value is lower than some studies have found in Iowa, possibly due to the challenge of growing cover crops in northern Iowa. Through work since 2007 in southeastern Iowa, we have found that drainage water management through controlled and shallow drainage reduce nitrate-N loss by about 45% when compared to conventional drainage. To reach the Gulf of Mexico Hypoxia nutrient reduction goals, it will take a combination of promising practices, including in-field and edge-of-field.