nutrient reduction strategy and best management …...cover crops (rye) on all cs and cc acres 28...
TRANSCRIPT
Nutrient Reduction Strategy and Best
Management PracticesMatthew 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 km2
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
In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result, somenitrate 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.
6
Water Flow Pathways
Land management and land use impacts ET and infiltration which in turn impact surface runoff, subsurface drainage, deep percolation
Naturally Well-Drained Soils Soils with Poor Natural Drainage
Nitrate-N Reduction PracticesPractice
% Nitrate-N Reduction [Average (Std. Dev.)]
% Corn Yield Change
Nitrogen Management
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)
Edge-of-Field
Controlled Drainage 33 (32)*
Shallow Drainage 32 (15)*
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 Reduction Practices
Practice% Phosphorus-P
Reduction [Average (Std. Dev.)]
% Corn Yield Change
Phosphorus Management
Producer does not apply phosphorus until STP drops
to optimal level17 (40) 0
No-till (70% residue) vs. conventional tillage (30%
residue)90 (17) -6 (8)
Cover Crops (Rye) 29 (37) -6 (7)
Land UsePerennial – Land retirement 75 (-)
Pasture 59 (42)
Edge-of-FieldBuffers 58 (32)
Terraces 77 (19)Assessment did not include stream bed and bank contributions although recognized as significant
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Reducing nitrogen application rate from background to the MRTN 133 lbN/ac on CB and to 190 lb N/ac on CC
9 -0.58 -32
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Reducing nitrogen application rate from background to the MRTN 133 lbN/ac on CB and to 190 lb N/ac on CC
9 -0.58 -32
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Cover crops (rye) on ALL CS and CC acres 28 5.96 50 60 1,025
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Soil Nitrate Production vs. Crop Nitrate UptakeAddition of a Cover Crop
March February
Rate of soil nitrate production from native soil organic matter
Rate of corn or soybean nitrate uptake
Cover crops can use nitrate when corn and beans are not growing, thus reducing the asynchrony between soil nitrate production and crop nitrate uptake.
Cover crop nitrate use
Cover crop nitrate use
In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result, some nitrate is lost to waterways.
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Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Install Wetlands to treat 45% of the ag acres 22 1.38 191
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
1 km
Targeted Wetland Restoration
Iowa Conservation Reserve Enhancement Program (CREP)
0 0.1 0.2 0.3 0.4Average hydraulic loading rate (m day-1)
0
20
40
60
80
100Pe
rcen
t nitr
ate
mas
s rem
oved
Modeled nitrate removal2004-2011 observed wetlands2012 observed wetlands
Source: W. Crumpton
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Install Wetlands to treat 45% of the ag acres 22 1.38 191
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
1 km
Targeted Wetland Restoration
Iowa Conservation Reserve Enhancement Program (CREP)
0 0.1 0.2 0.3 0.4Average hydraulic loading rate (m day-1)
0
20
40
60
80
100Pe
rcen
t nitr
ate
mas
s rem
oved
Modeled nitrate removal2004-2011 observed wetlands2012 observed wetlands
Source: W. Crumpton
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Install Denitrification Bioreactors on all tile drained acres 18 0.92 101
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Perennial crops (energy crops) on ~6.5 million acres 18 21.46 29 238 2,318
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nitrate Removal Wetlands
Cover Crops
Subsurface Drainage Bioreactors
Saturated Buffers
Prairie Strips
Overall Comparison of Nitrate-N PracticesNitrate-N
ReductionCost of N Reduction
OtherBenefits
(Ecosystem Services)
Practice/Scenario % (from baseline) ($/lb)
Reducing nitrogen application rate from background to the MRTN 9 -0.58
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 2 1.29
Perennial crops (energy crops) on ~6.5 million acres 18 21.46 ++
Overall Comparison of Phosphorus Practices
PReduction
Cost of P Reduction
OtherBenefits
(Ecosystem Services)
Practice/Scenario % (from baseline) ($/lb)
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 7 -110
Establish streamside buffers (35ft) on all crop land 18 14 ++
Perennial crops (energy crops) equal to pasture/hay acreage from 1987 29 238 ++
Pasture and Land Retirement to equal acreage of Pasture/Hay and CRP from 1987 9 120 ++
What Might it Take to Reach our Goals?
Nitrate-N Reduction
Practice/Scenario % (from baseline)
N management - Maximum Return to Nitrogen Application Rate and 60% of all Corn-Bean and Continuous Corn Acres with Cover CropEdge-of-Field - 27% of all ag land treated with wetland and 60% of all subsurface drained land with bioreactor
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Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Reduction Strategy
What Might it Take to Reach our Goals?
Nitrate-N Reduction
Practice/Scenario % (from baseline)
N management - Maximum Return to Nitrogen Application Rate and 25% of all Corn-Bean and Continuous Corn Acres with Cover CropLand Use - 25% of acreage with Extended RotationsEdge-of-Field - 27% of all ag land treated with wetland and 60% of all subsurface drained land with bioreactor
42
Example: Combination Scenarios that Achieves N Goal From Non-Point Sources for Nutrient Reduction Strategy
Summary• The Iowa Nutrient Reduction 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?