Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 1/15/2005
Publication Date: 1/15/2005
Citation: Petrolia, D.R., Gowda, P., Mulla, D.J. 2005. Targeting agricultural drainage to reduce nitrogen losses in a Minnesota watershed. Staff Paper P05-02, Department of Applied Economics, University of Minnesota, St. Paul, Minnesota. Experiment Station Bulletins. 16 p. Interpretive Summary: The Mississippi-Atchafalaya River Basin drains 1.6 million metric tons of nitrogen each year into the Gulf of Mexico, with 61 percent of that as nitrate-nitrogen causing hypoxic conditions along the northern Gulf coast. The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force set a coastal goal of reducing areal extent of hypoxia in the Gulf to 5,000 sq. km. by 2015. They estimated that this would require a 30 percent reduction in nitrogen discharges from the Mississippi and Atchafalaya Rivers to the Gulf. It is well known that subsurface tile drainage is a major pathway for agricultural nitrogen losses and more than 30 percent of the crop land in the Upper Midwest is tile drained. In this study, a linear-optimization model was used to evaluate the environmental and economic impact of subsurface drainage focused abatement policies for reducing nitrogen losses. Results indicate that it is not cost-effective to remove tile-drained land from production or to remove/plug tile lines because of its value to agricultural production.
Technical Abstract: Agricultural nitrogen losses are the major contributor to nitrogen loads in the Mississippi River, and consequently, to the existence of a hypoxic, or “dead”, zone in the Gulf of Mexico. Focusing on two small agricultural watersheds in southeast Minnesota, simulation results from the Agricultural Drainage and Pesticide Transport (ADAPT) model were combined with a linear-optimization model to evaluate the environmental and economic impact of alternative land-use policies for reducing nitrogen losses. Of particular importance was the study’s explicit focus on agricultural subsurface (tile) drainage, which has been identified as the major pathway for agricultural nitrogen losses in the Upper Midwest, and the use of drainage-focused abatement policies. Results indicate that tile-drained land plays a key role in nitrogen abatement, and that a combined policy of nutrient management on tile-drained land and retirement of non-drained land is a cost-effective means of achieving a 20- or 30-percent nitrogen abatement goal. Results also indicate that although it is cost-effective to abate on tile drained land, it is not cost-effective to undertake policies that plug or remove tile drains from the landscape, regardless of whether the land would be retired or kept in production. Therefore, results imply that although tile-drained land is a major source of nitrogen lost to waterways, it is not cost effective to remove the land from production or to remove the drainage from the land. Because of its value to agricultural production, it is better to keep tile-drained land in production under nutrient management and focus retirement policies on relatively less-productive, non-drained acres.