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Dr. Matt Helmers - Reducing Nitrate-N: Scale of Implementation Needed
The document discusses the increasing concerns over nitrate-n levels in local waters due to agricultural practices, highlighting the necessity for comprehensive reduction strategies in the Mississippi/Atchafalaya River Basin. It emphasizes the role of cover crops and nitrogen management practices in decreasing nitrate loss and outlines the significant implementation scale required to achieve a 41% reduction in nitrate-n from nonpoint sources as per Iowa's nutrient reduction strategy. The findings underscore the need for both in-field and edge-of-field practices to meet these environmental goals.
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Dr. Matt Helmers - Reducing Nitrate-N: Scale of Implementation Needed
- 1. Department of Agriculturaland Biosystems Engineering Reducing Nitrate-N: Scale of Implementation Needed Matthew Helmers Dean’s Professor, College of Ag. & Life Sciences Professor, Dept. of Ag. and Biosystems Eng. Iowa State University Department of Agricultural and Biosystems Engineering
- 2. Situation • Increasing concernfor local and regional waters • Substantial demand for agricultural products • Hypoxia Action Plan in 2008 called for development and implementation of comprehensive N and P reduction strategies for states in the Mississippi/Atchafalaya River Basin • Des Moines Waterworks has filed a lawsuit over high nitrate-N levels
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- 4. 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Average Drainage(in) 0 5 10 15 20 25 30 Nitrate-nitrogenConcentration(ppm) 0 5 10 15 20 25 30 Nitrate-nitrogenLoss(lb-N/ac) 0 20 40 60 80Drainage Nitrate-N Concentration Nitrate-N Loss Corn-SoybeanRotation 150/160 lb-N/acre Application Rate Variability in Drainage, Nitrate Concentration and Nitrate Loss
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- 6. Four-year Average Nitrate-NitrogenConcentrations for Treatments at Gilmore City Fallam m onia 150 Spring am m onia 150Fallm anureSpring m anure Fallm anure C &S Fallam m onia 225 Spring am m onia 225 Nitrate-nitrogenconcentration(mgL-1 ) 0 5 10 15 20 25 30 c c bc b a b a Note: Treatment means with different letters above the bar are significantly (P<0.05) different Source: Lawlor et al., 2011 Note: Manure applications were 200 lb-N/acre to corn for Fall and Spring Manure treatments and 150 lb-N/acre to corn and Soybeans in the Fall manure C&S treatment
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- 8. Soil Nitrate Productionvs. Crop Nitrate Uptake In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result, some nitrate is lost to waterways. March February Rate of soil nitrate production from native soil organic matter Rate of corn or soybean nitrate uptake The majority of nitrate used by corn and soybean comes from soil nitrate production. Corn gets the difference from fertilizer while soybean gets the difference from legume fixation of atmospheric nitrogen.
- 9. Winter Cereal RyeCover Crops Ames Gilmore City
- 10. Soil Nitrate Productionvs. Crop Nitrate Uptake Addition of a Cover Crop March February Rate of soil nitrate production from native soil organic matter Rate of corn or soybean nitrate uptake Cover crops can use nitrate when corn and beans are not growing, thus reducing the asynchrony between soil nitrate production and crop nitrate uptake. Cover crop nitrate use Cover crop nitrate use In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result, some nitrate is lost to waterways.
- 11. Impacts of CoverCrops on Nitrate-N Concentration in Drainage Water – Gilmore City – System with Tillage ~25% Reduction in Nitrate-N Concentration With Winter Cereal Rye Cover Crop
- 12. Subsurface Drainage and Nitrate-NLeaching 2010-2013 Subsurface D rainage N itrate-N C oncentration N itrate-N Load SubsurfaceDrainage(in) 0 5 10 15 20 Flow-weightedNitrate-N Concentration(ppm) 0 5 10 15 20 AnnualNitrate-NLoad(lb/acre) 0 5 10 15 20 CORN-soybean SOYBEAN-corn Continuous Corn Continuous Corn with Cover Crop Prairie Fertilized Prairie
- 13. What Can WeDo?
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- 17. From Christianson andHelmers, 2011 Illustration by John Petersen (www.petersenart.com) Subsurface Drainage Bioreactor
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- 20. Corn Soybean 1 km Targeted WetlandRestoration DD Tile W.G. Crumpton, Iowa State University Iowa Conservation Reserve Enhancement Program (CREP)
- 21. What Might itTake to Reach our Goals? Nitrate-N Reduction Total Equal Annualized Cost Practice/Scenario % (from baseline) Million $/yr N management - Maximum Return to Nitrogen Application Rate and 60% of all Corn-Bean and Continuous Corn Acres with Cover Crop Edge-of-Field - 27% of all ag land treated with wetland and 60% of all subsurface drained land with bioreactor 42 756 Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Reduction Strategy
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- 25. Wrapup • Iowa NutrientReduction Strategy calls for a 41% reduction in nitrate-N from nonpoint sources • In-field nitrogen management has some potential to reduce nitrate-N loss however other in-field and edge-of-field practices will be needed to reach the goals • Level of implementation to reach the goals is very large
- 26. Contact • mhelmers@iastate.edu • Twitter:@ISUAgWaterMgmt • Website: http://agwatermgmt.ae.iastate.edu/
Editor's Notes
- #9 Fall application.
- #22 Examples for illustration only, not for recommendation. It shows that to achieve the 41% N and 29% P targets for nonpoint source, it will require a high adoption rate of several practices. Remember that Equal Annualized Costs (EAC) includes the annualized initial investment, so you cannot add initial investment and EAC.