Economic and Environmental Impacts of LSNT and Cover Crops for Nitrate-Nitrogen Reduction in Walnut Creek Watershed, Iowa, Using FEM and Enhanced SWAT Models

Nitrate nitrogen (NO 3 -N) enriched water originates from subsurface drains or "tiles" that underlay many fields in the Corn Belt and is the primary source of NO 3 -N to surface waters in this region. To better assess the fate and transport of nutrients, such as NO 3 -N, the tile drain and pothole components of SWAT (Soil and Water Assessment Tool) were enhanced and modified in the previous component of this study. In this study, the environmental and economic impacts of various best management practice (BMP) scenarios often adopted by local farmers to reduce sediment and nutrient loadings (in particular NO 3 -N) were evaluated using the modified SWAT (SWAT-M) and FEM (Farm-level Economic Model) models. Measured values of water quality indicators from the Walnut Creek watershed (WCW) located in central Iowa were used to verify the capability of SWAT-M to predict the impact of late-spring nitrate test (LSNT) and rye cover crop management on NO 3 -N reduction at the subbasin level. The results obtained from SWAT-M simulation results, similar to field measurement data, indicated a 25% reduction in NO 3 -N under the LSNT scenario. FEM results indicated a corresponding increased annual cost of $6/ha across all farms in the watershed. Simulation of other scenarios, including winter cover cropping and a combination of LSNT and cover cropping at different adoption rates within WCW, resulted in a progressive reduction in sediment and nutrient losses as adoption rates increased. Use of the rye cover crop added about $25/ha to $35/ha to the annual cost of the average farm, indicating that some cost-share support may be necessary to encourage farmers to use winter cover crops.

[1]  Martin J. Shipitalo,et al.  Nitrate Leaching through Lysimeters in a Corn-Soybean Rotation , 1995 .

[2]  H. Aronsson,et al.  Measured and simulated availability and leaching of nitrogen associated with frequent use of catch crops , 1998 .

[3]  D. Walters,et al.  Winter rye cover crop following soybean under conservation tillage : Residual soil nitrate , 1999 .

[4]  Arnold,et al.  CONTINENTAL SCALE SIMULATION OF THE HYDROLOGIC BALANCE 1 , 1999 .

[5]  L. Hewes,et al.  Occupying the Wet Prairie: The Role of Artificial Drainage in Story County, Iowa , 1952 .

[6]  W. Simpkins,et al.  Geology, Groundwater Flow, and Water Quality in the Walnut Creek Watershed , 1999 .

[7]  John H. Prueger,et al.  Water Quality in Walnut Creek Watershed: Setting and Farming Practices , 1999 .

[8]  K. Reddy,et al.  Water quality effects of drainage in humid regions. , 1999 .

[9]  D. Karlen,et al.  Using the late spring nitrate test to reduce nitrate loss within a watershed. , 2004, Journal of environmental quality.

[10]  J. Doe.  The Soil Scientist , 1964 .

[11]  F. Magdoff,et al.  A Soil Test for Nitrogen Availability to Corn , 1984 .

[12]  Jerry L. Hatfield,et al.  Water Quality in Walnut Creek Watershed: Herbicides and Nitrate in Surface Waters , 1999 .

[13]  P. Gassman,et al.  APPLICATION OF AN ENVIRONMENTAL AND ECONOMIC MODELING SYSTEM FOR WATERSHED ASSESSMENTS 1 , 2002 .

[14]  J. Hatfield,et al.  Review and Interpretation: Nitrogen Management Strategies to Reduce Nitrate Leaching in Tile-Drained Midwestern Soils , 2002 .

[15]  G W Randall,et al.  Nitrate nitrogen in surface waters as influenced by climatic conditions and agricultural practices. , 2001, Journal of environmental quality.

[16]  Jeffrey G. Arnold,et al.  DEVELOPMENT AND APPLICATION OF SWAT TO LANDSCAPES WITH TILES AND POTHOLES , 2005 .

[17]  Philip W. Gassman,et al.  Application of the Comprehensive Economic and Environmental Optimization Tool (CEEOT) for Evaluating BMPs , 2005 .

[18]  M. Alley,et al.  Effectiveness of winter rye for accumulating residual fertilizer N following corn , 1993 .

[19]  J. Webb,et al.  Effects of overwinter cover on nitrate loss and drainage from a sandy soil: consequences for water management? , 1999 .

[20]  Quay Dortch,et al.  Nutrient changes in the Mississippi River and system responses on the adjacent continental shelf , 1996 .

[21]  J. Braden,et al.  Nitrate abatement practices, farm profits, and lake water quality: A central Illinois case study , 2000 .

[22]  B. Babcock.  Effects of Uncertainty on Optimal Nitrogen Applications (The) , 1992 .