Nitrate-N Loss Reduction: Scale of In- Field and Edge-of-Field Practice Implementation to Reach Water Quality Goals

Transcription

1 Department of Agricultural and Biosystems Engineering Nitrate-N Loss Reduction: Scale of In- Field and Edge-of-Field Practice Implementation to Reach Water Quality Goals Matthew Helmers Dean s Professor, College of Ag. & Life Sciences Professor, Dept. of Ag. and Biosystems Eng. Iowa State University

2 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

3 To Reach our Goals WE NEED IT ALL!! N Management Cropping practices/landuse Edge-of-Field Practices Department of Agricultural and Biosystems Engineering

4 N-Mgt Land Use Nitrate-N Reduction Practices Practice % Nitrate-N Reduction [Avg. (Std. Dev.)] Cost of N Reduction ($/lb) Timing (Fall to spring) 6 (25) -283 Nitrogen Application Rate (MRTN rate MRTN) Nitrification Inhibitor (nitrapyrin) 9 (19) Cover Crops (Rye) 31 (29) 5.96 Perennial Pasture/Land retirement 85 (9) 9.12 Perennial Energy Crops 72 (23) Extended Rotations 42 (12) 2.7 Controlled Drainage 33 (32)* 1.29 Shallow Drainage 32 (15)* Edge-of- Field Wetlands Bioreactors 43 (21) 0.92 Buffers 91 (20)** 1.91 Saturated Buffers 50 (13) *Load reduction not concentration reduction **Concentration reduction of that water interacts with active zone below the buffer

5 N-Mgt Land Use Nitrate-N Reduction Practices Practice % Nitrate-N Reduction [Avg. (Std. Dev.)] Cost of N Reduction ($/lb) Timing (Fall to spring) 6 (25) -283 Nitrogen Application Rate (MRTN rate MRTN) Nitrification Inhibitor (nitrapyrin) 9 (19) Cover Crops (Rye) 31 (29) 5.96 Perennial Pasture/Land retirement 85 (9) 9.12 Perennial Energy Crops 72 (23) Extended Rotations 42 (12) 2.7 Controlled Drainage 33 (32)* 1.29 Shallow Drainage 32 (15)* Edge-of- Field Wetlands Bioreactors 43 (21) 0.92 Buffers 91 (20)** 1.91 Saturated Buffers 50 (13) *Load reduction not concentration reduction **Concentration reduction of that water interacts with active zone below the buffer

6 N-Mgt Land Use Nitrate-N Reduction Practices Practice % Nitrate-N Reduction [Avg. (Std. Dev.)] Cost of N Reduction ($/lb) Timing (Fall to spring) 6 (25) -283 Nitrogen Application Rate (MRTN rate MRTN) Nitrification Inhibitor (nitrapyrin) 9 (19) Cover Crops (Rye) 31 (29) 5.96 Perennial Pasture/Land retirement 85 (9) 9.12 Perennial Energy Crops 72 (23) Extended Rotations 42 (12) 2.7 Controlled Drainage 33 (32)* 1.29 Shallow Drainage 32 (15)* Edge-of- Field Wetlands Bioreactors 43 (21) 0.92 Buffers 91 (20)** 1.91 Saturated Buffers 50 (13) *Load reduction not concentration reduction **Concentration reduction of that water interacts with active zone below the buffer

7 N-Mgt Land Use Nitrate-N Reduction Practices Practice % Nitrate-N Reduction [Avg. (Std. Dev.)] Cost of N Reduction ($/lb) Timing (Fall to spring) 6 (25) -283 Nitrogen Application Rate (MRTN rate MRTN) Nitrification Inhibitor (nitrapyrin) 9 (19) Cover Crops (Rye) 31 (29) 5.96 Perennial Pasture/Land retirement 85 (9) 9.12 Perennial Energy Crops 72 (23) Extended Rotations 42 (12) 2.7 Controlled Drainage 33 (32)* 1.29 Shallow Drainage 32 (15)* Edge-of- Field Wetlands Bioreactors 43 (21) 0.92 Buffers 91 (20)** 1.91 Saturated Buffers 50 (13) *Load reduction not concentration reduction **Concentration reduction of that water interacts with active zone below the buffer

8 How Does Nitrate Leaching Vary from Year to Year?

9 Twenty-Five Year Summary of Nitrate-N Concentration Nitrate-nitrogen Concentration (ppm) Nitrate-N Concentration What is Different over this Period? Avg.

10 Twenty-Five Year Summary of Nitrate-N Concentration Nitrate-nitrogen Concentration (ppm) Nitrate-N Concentration Avg. Combined Corn-Soybean System Same N management Early Spring Sidedress at lb-n/acre

11 Twenty-Five Year Summary of Leaching Volume Drainage (in) Leaching Volume Avg. Combined Corn-Soybean System Same N management Early Spring Sidedress at lb-n/acre

12 Twenty-Five Year Summary of Nitrate-N Loss Nitrate-nitrogen Loss (lb-n/ac) Nitrate-N Loss Avg. Combined Corn-Soybean System Same N management Early Spring Sidedress at lb-n/acre

13 Twenty-Five Year Summary Drainage (in) Leaching Volume Nitrate-N Concentration Nitrate-N Loss Avg. Combined Corn-Soybean System Same N management Early Spring Sidedress at lb-n/acre Nitrate-nitrogen Concentration (ppm) Nitrate-nitrogen Loss (lb-n/ac)

14 Impact of Application Timing: kg-n/ha 168 kg-n/ha

15 Impact of Application Timing: kg-n/ha 168 kg-n/ha

16 Nitrate Response to Nitrogen

17 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.

18 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. As a result, some nitrate is lost to waterways.

19 Winter Cereal Rye Cover Crops Ames Gilmore City

20 Impacts of Cover Crops on Nitrate-N Load in Drainage Water Gilmore City 36% Reduction 34% Reduction

21 Impacts of Land Use Change 180 NO3-N Load (kg N/ha) Corn/Soybean Continuous Corn Continuous Corn with Cover Crop Prairie Fertilized Prairie /1/10 1/1/11 1/1/12 1/1/13 1/1/14 1/1/15 1/1/16

22 Subsurface Drainage Bioreactor From Christianson and Helmers, 2011 Illustration by John Petersen

23 Example Bioreactor 2D Graph Performance 2 30 Nitrate-N Concentration (mg/l) Inflow Outflow Department of Agricultural and Biosystems Engineering

24 Nitrate Removal Wetland

25 Iowa Conservation Reserve Enhancement Program (CREP) Targeted Wetland Restoration Corn Soybean DD Tile 1 km W.G. Crumpton, Iowa State University

26 Hydrologic and nutrient loading rates are major drivers of wetland performance. Wetlands occupying only 1% of landscape can reduce long term average nitrate loads about 52%. From: W.G. Crumpton

27 Drainage water management

28 DWM reduces drainage amount Data: Matt Helmers, Iowa State University

29 DWM has little impact on NO 3 concentration Source: Matt Helmers, Iowa State University

30 DWM reduces N load Data: Matt Helmers, Iowa State University

31 Saturated buffers

32 Source: Christianson et al. (in press) Saturated buffers Conventional outlet Outlet with saturated buffer

33 Drainage water recycling

34 Photo: Giorgi Chighladze transformingdrainage.org Drainage water recycling Reducing drain flow

35 What Might it Take to Reach our Goals? Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Reduction 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 Reduction % (from baseline) Total Equal Annualized Cost Million $/yr

36 Treated Acres

37 Treated Acres ~7600 wetlands

38 ~7600 wetlands ~ bioreactors Treated Acres

39 Wrapup 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

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