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A Risk Evaluation of Nitrate Loading to Groundwater Supplies in Freeborn County: a biofuel production modeling study

Background. USA:81.8 million acres Corn in 2006, 86 mil. acres by 2012Corn prices exceed $6.00/bu, Soybeans $12.50/buLand currently under CRP contract for the 2008 crop year: 34.66 million acres, down 2.11 million acres from 36.77 million acres in 2007. States with the largest CRP declines: Nort

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A Risk Evaluation of Nitrate Loading to Groundwater Supplies in Freeborn County: a biofuel production modeling study

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    1. A Risk Evaluation of Nitrate Loading to Groundwater Supplies in Freeborn County: a biofuel production modeling study

    2. Background USA: 81.8 million acres Corn in 2006, 86 mil. acres by 2012 Corn prices exceed $6.00/bu, Soybeans $12.50/bu Land currently under CRP contract for the 2008 crop year: 34.66 million acres, down 2.11 million acres from 36.77 million acres in 2007. States with the largest CRP declines: North Dakota and South Dakota, with losses of 400,000 and 248,000 acres, respectively.

    3. Background Minnesota: 1997: 10% ethanol blend; 2005: 2% biodiesel blend 2013: 20% ethanol blend proposed In 2008, 1 billion gallons Ethanol, 25% of corn crop CO2 emissions 31% 1990-2005, mostly from driving 1.83 million acres in CRP – 70,000 acres expire in 2010 Freeborn County: Number of farms: 1,172 in 2002, 1,193 in 1997 (-2% ) Land in farms: 394,408 acres in 2002, 376,923 acres in 1997 (5% ) Average farm size: 337 acres in 2002, 316 acres in 1997 (7% ) 6071 acres in CRP – 500 acres expire in 2010

    5. Health Concerns Well water in rural communities Nitrate leaching to sensitive aquifers ? health risks. Safe drinking water MCL: 10 ppm nitrate-N (SDWA 1974)

    6. Agricultural BMPs and Local Management Fall application of manure and fertilizer N common Loss of CRP acres 20-50 lbs/ac fertilizer N trimmed without corn yield loss (MDA FANMAP study, 1999) Annual crop systems in 10 year time of travel for wells in many rural water supply districts

    14. Objective of Study Use the computer simulation model GLEAMS and Geographic Information Systems software (ArcGIS) to identify areas of concern and explore alternative management systems for farmland adapting to the new Biofuel initiatives.

    16. GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) One-dimensional, field-scale, continuous flow model Evaluate effects of agricultural management systems on chemical and nutrient movement

    17. Model Parameters Nutrient: crop management, fertility, timing, field operations Hydrology: soil parameters, mean monthly max. and min. temps, planting and harvest dates, irrigation rates, daily precipitation summaries Erosion: field parameters (slope, contour, curve numbers, % cover, K values)

    18. Model Calibration/Validation

    20. Treatments Precipitation: 10 years of continuous data (1996-2005) Multiple soil types based on county soil survey Two crops: Continuous Corn and Corn-Soybean rotation Dryland (no irrigation) and model applied irrigation Fertilizer application: 150 lb./ac. on Continuous Corn, and 100 lb./ac. on Corn in Corn-Soybean rotation

    21. Digital Soils Data

    26. Results U of M Extension in Freeborn County can use results, in conjunction with farmers, to revise Best Management Practices (BMPs) currently in use Possible solutions include: Retention of lands enrolled in conservation programs (CRP, CREP, easements, etc.) Reduce amount of N present in leachate/runoff, i.e. less fertilizer, follow current BMPs, spring application Conversion of annual-cropped areas of concern to perennial crops

    27. Annual vs. Perennial Crops Annual less water use short growing season non-legumes need fertilizer N have moderate N uptake capacity limited tolerance for saturated rootzone Perennial more water use longer growing season normally don’t need fertilizer N (legumes, CRP) some have high N uptake capacity some tolerate saturated rootzones

    28. Continuous corn and corn/soybean are leaky Perennials are not (usually)

    29. Conclusions Simulation models + GIS can: adequately estimate mass of leachable NO3-N ID and delineate areas of concern conduct condition-specific examinations locate areas most likely to benefit from intervention guide recommendations for watershed management districts or CRP program enrollment BMPs for these areas should be re-examined ? acreage of annual crops results in ? nitrate-loading to sensitive groundwater systems

    30. Next Steps Couple simulation model output to GIS: GLEAMS model output now extracted by Excel macro, brought into GIS in multi-step process Include student assistance in developing GIS layers, especially SSURGO soils, for more MN counties Incorporate updated CRP data into study areas

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