THE IMPACT OF POLICY AND ECONOMIC DRIVERS OF CORN PRODUCTION ON NITROGEN LEVELS OF THE BUFFALO RIVER SUBBASIN, MINNESOTA, 2006–2014

From 2006 to 2013, corn cultivation in the Buffalo River subbasin of Minnesota has increased from 20,092 to 59,033 hectares. It is expected that this large change in corn production has adversely affected water quality. This study looks at the changes in profitability for various land uses within the Buffalo River subbasin and subsequent changes in water quality.

Variables are identified which influence land owners’ land use decisions, including regulations which influence profitability such as policies that stimulate ethanol production. The economic impact of these and factors such as yields, prices and costs are used to construct an economic model that identifies the land use that will maximize profits for land managers. The economic model is validated using National Agricultural Statistics Service data. Correlation analysis of the profit-maximizing land use and empirical land use data is used to identify relationships between policies, economics and land use. The product of this analysis is a validated economics and land use model.

Having identified land use change within the subbasin, the impact of this change on water quality is assessed. Analysis of water quality data at the mouth of the Buffalo River shows that the nitrate levels have increased at a rate of 0.040 mg/L per year since 2005. Digital delineation of areas of the watershed corresponding to eight water quality gages within the study area and correlation analysis of the land use and water quality will identify relationships between changes in land use and water quality. It is expected that this delineation and the statistical analysis of land use and water quality will identify increasing trends in surface water nitrate within areas where corn production has increased.

This study will provide decision makers with perspective regarding the consequences of policy and land use changes. This work is a preliminary assessment of the study area which will be followed by a Soil and Water Assessment Tool (SWAT) modeling of the area of interest. SWAT will evaluate how the land use change has impacted water quality and explore the influences of various policy, economic and management practice scenarios. These studies are components of a larger study, USDA NIFA Project No. 2013-03902.