Nutrient Strategy and Best Management Practices Matthew Helmers Dean s Professor, College of Ag. & Life Sciences Professor, Dept. of Ag. and Biosystems Eng. Iowa State University
Situation Increasing concern for 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 Increasing concern about phosphorus loading to Lake Erie and the role of drainage in this loading
Gulf of Mexico Hypoxia Goals Hypoxia Action Plan Goal: Reduce the size of the zone to 5,000 km 2 by 2015 EPA-SAB Recommendations: Reduce Total Riverine Nitrogen and Phosphorus Loads by 45%
Current and Pending Programs States in the Mississippi River Basin are implementing state nutrient reduction strategies These strategies are a voluntary approach to reducing nutrient loading to downstream waters Increasing demand to document water quality improvements and increasing demand for accountability Increasing discussion about regulation
Timing of Subsurface Drainage (1990-2011)
Soil Nitrate Production vs. Crop Nitrate Uptake 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. March February 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. 6
Water Flow Pathways Naturally Well-Drained Soils Soils with Poor Natural Drainage Land management and land use impacts ET and infiltration which in turn impact surface runoff, subsurface drainage, deep percolation
Nitrogen Management Nitrate-N Practices Practice % Nitrate-N [Average (Std. Dev.)] % Corn Yield Change Timing (Fall to spring) 6 (25) 4 (16) Nitrogen Application Rate (MRTN rate MRTN) 10-1 Nitrification Inhibitor (nitrapyrin) 9 (19) 6 (22) Cover Crops (Rye) 31 (29) -6 (7) Land Use Perennial Pasture/Land retirement 85 (9) Perennial Energy Crops 72 (23) Extended Rotations 42 (12) 7 (7) Controlled Drainage 33 (32)* Shallow Drainage 32 (15)* Edge-of-Field Wetlands 52 Bioreactors 43 (21) Buffers 91 (20)** Saturated Buffers 50 (13) *Load reduction not concentration reduction **Concentration reduction of that water interacts with active zone below the buffer
Phosphorus Practices Practice % Phosphorus-P [Average (Std. Dev.)] % Corn Yield Change Phosphorus Management Producer does not apply phosphorus until STP drops to optimal level No-till (70% residue) vs. conventional tillage (30% residue) 17 (40) 0 90 (17) -6 (8) Cover Crops (Rye) 29 (37) -6 (7) Land Use Perennial Land retirement 75 (-) Pasture 59 (42) Buffers 58 (32) Edge-of-Field Terraces 77 (19) Assessment did not include stream bed and bank contributions although recognized as significant
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario Reducing nitrogen application rate from background to the MRTN 133 lb N/ac on CB and to 190 lb N/ac on CC (million $/yr) 9-0.58-32 From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario Reducing nitrogen application rate from background to the MRTN 133 lb N/ac on CB and to 190 lb N/ac on CC (million $/yr) 9-0.58-32 From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario (million $/yr) Cover crops (rye) on ALL CS and CC acres 28 5.96 50 60 1,025 From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Soil Nitrate Production vs. Crop Nitrate Uptake Addition of a Cover Crop 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 March February In the shaded areas, the soil produces nitrate, but there is no crop to use it. some nitrate is lost to waterways. As a result, 7
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario (million $/yr) Install Wetlands to treat 45% of the ag acres 22 1.38 191 Iowa Conservation Reserve Enhancement Program (CREP) 1 km Targeted Wetland Restoration Percent nitrate mass removed 100 80 60 40 20 0 0 0.1 0.2 0.3 0.4 Average hydraulic loading rate (m day -1 ) Modeled nitrate removal 2004-2011 observed wetlands 2012 observed wetlands Source: W. Crumpton From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario (million $/yr) Install Wetlands to treat 45% of the ag acres 22 1.38 191 Iowa Conservation Reserve Enhancement Program (CREP) 1 km Targeted Wetland Restoration Percent nitrate mass removed 100 80 60 40 20 0 0 0.1 0.2 0.3 0.4 Average hydraulic loading rate (m day -1 ) Modeled nitrate removal 2004-2011 observed wetlands 2012 observed wetlands Source: W. Crumpton From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario (million $/yr) Install Denitrification Bioreactors on all tile drained acres 18 0.92 101 From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Scenarios Nitrate-N Cost of N Phosphorus Cost of P Total Equal Annualized Cost Practice/Scenario (million $/yr) Perennial crops (energy crops) on ~6.5 million acres 18 21.46 29 238 2,318 From Iowa Nutrient Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nitrate Removal Wetlands
Cover Crops
Subsurface Drainage Bioreactors
Saturated Buffers
Prairie Strips
Overall Comparison of Nitrate-N Practices Practice/Scenario Reducing nitrogen application rate from background to the MRTN Nitrate-N Cost of N 9-0.58 Other Benefits (Ecosystem Services) Cover crops (rye) on ALL CS and CC acres 28 5.96 ++ Install Wetlands to treat 45% of the ag acres 22 1.38 ++ Install Denitrification Bioreactors on all tile drained acres 18 0.92 Install Buffers on all applicable lands 7 1.91 ++ Installing Controlled Drainage on all applicable acres Perennial crops (energy crops) on ~6.5 million acres 2 1.29 18 21.46 ++
Overall Comparison of Phosphorus Practices Practice/Scenario P Cost of P Other Benefits (Ecosystem Services) Cover crops (rye) on ALL CS and CC acres 50 60 ++ Convert all tillage to no-till 39 14 ++ P rate reduction in MLRA s that have high to very high soil test P Establish streamside buffers (35ft) on all crop land Perennial crops (energy crops) equal to pasture/hay acreage from 1987 Pasture and Land Retirement to equal acreage of Pasture/Hay and CRP from 1987 7-110 18 14 ++ 29 238 ++ 9 120 ++
What Might it Take to Reach our Goals? Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Strategy Practice/Scenario 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 Nitrate-N 42
What Might it Take to Reach our Goals? Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Strategy Practice/Scenario N management - Maximum Return to Nitrogen Application Rate and 25% of all Corn-Bean and Continuous Corn Acres with Cover Crop Land Use - 25% of acreage with Extended Rotations Edge-of-Field - 27% of all ag land treated with wetland and 60% of all subsurface drained land with bioreactor Nitrate-N 42
Summary The Iowa Nutrient Strategy is a statewide effort to reduce nutrient loading To reach the goals will take broad implementation of multiple practices Are there opportunities to implement practices that enhance or protect long-term value of the land?