iowa nutrient reduction strategy science assessment · department of agricultural and biosystems...
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Department of Agricultural and Biosystems Engineering
Iowa Nutrient Reduction Strategy Science
AssessmentMatthew 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
Iowa Nutrient Reduction Strategy – Science Team• Matt Helmers – ISU – N Team
Lead• Tom Isenhart – ISU – P Team Lead• John Lawrence – ISU• John Sawyer – ISU• Antonio Mallarino – ISU• William Crumpton – ISU• Rick Cruse – ISU• Mike Duffy – ISU• Reid Christianson – ISU• Phil Gassman – ISU• Dean Lemke – IDALS• Shawn Richmond – IDALS
• Jim Baker – IDALS/ISU• Keith Schilling – IDNR• Calvin Wolter – IDNR• Dan Jaynes – USDA-ARS• Mark Tomer – USDA-ARS• John Kovar – USDA-ARS• David James – USDA-ARS• Eric Hurley – USDA-NRCS• Mark David – Univ. of Illinois• Gyles Randall – Univ. of Mn• Katie Flahive - USEPA
Department of Agricultural and Biosystems Engineering
Approach1. Establish baseline – existing conditions2. Conduct an extensive literature review to assess
potential performance of practices• Outside peer review of science team documents (practice
performance and baseline conditions)3. Estimate potential load reductions of
implementing nutrient reduction practices (scenarios)• “Full implementation” and “Combined” scenarios
4. Estimate cost of implementation and cost per pound of nitrogen and phosphorus reduction
Estimated Nitrogen Application Rate –Manure + Fertilizer
Rate on CB Rate on CC
MLRA lb N/ac lb N/ac102C 182 232103 154 204104 144 194105 131 181107A 184 234107B 139 189108C 163 213108D 120 170109 142 192115C 146 196
Iowa Total 151 201
Maximum Return to Nitrogen from corn following soybean with $5/bushel corn and $0.5/lb of N = 133 lb-N/acre for CB (profitable range of 121-146 lb/acre) and 190 lb-N/acre for CC (profitable range of 177-202 lb-N/acre)
MLRAAverage STP of each
MLRAmg P/kg soil
103 30104 27105 27107A 32107B 28108C 27108D 19109 11
Soil Test Phosphorous Concentrations
Optimum STP = 20 mg P/kg soil
Practice Review Process• Extensive review of literature from Iowa and
surrounding states – Used Iowa and surrounding states to try to
have similar soils and climatic conditions– Reviewed and compiled impacts on nitrogen
and phosphorus concentrations and loads– Reviewed and compiled impacts on corn yield
• Summarized expected practice performance
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 (Reduce rate to 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)***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 $/yr)
Cover crops (rye) on ALL CS and CC acres 28 5.96 50 60 1,025
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/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 $/yr)
Install Buffers on all applicable lands (30 ft. on each side of stream) 7 1.91 18 14 88
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction on Nitrogen and 29% reduction on Phosphorus
100% Crop 100% Prairie10% Prairie ‐ 90% Crop
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Install Controlled Drainage on all applicable acres 2 1.29 18
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Perennial crops (energy crops) on ~6.5 million acres 18 21.46 29 238 2,318
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Nutrient Load Reduction Scenarios
Nitrate-N Reduction
Cost of N Reduction
Phosphorus Reduction
Cost of P Reduction
Total Equal Annualized
Cost
Practice/Scenario % (from baseline) ($/lb) % (from
baseline) ($/lb) (million $/yr)
Convert all tillage to no-till 39 14 186.4
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction in Nitrogen and 29% reduction in Phosphorus
Overall Comparison of Nitrate-N PracticesNitrate-N
ReductionCost of N Reduction
OtherBenefits
(Ecosystem Services)
Practice/Scenario % (from baseline) ($/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 ++
Example: Combination Scenarios that Achieve N and P Goal From Non-Point Sources
From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction on Nitrogen and 29% reduction on Phosphorus
Nitrate-N Reduction
Phosphorus Reduction
Initial Investment
Total Equal Annualized
Cost
Statewide Average EAC
Costs
Practice/Scenario % (from baseline)
% (from baseline) (million $)
(million $/yr) ($/acre)
MRTN Rate, 60% Acreage with Cover Crop, 27% of ag land treated with wetland and 60% of drained land has bioreactor
42 30 3,218 756 36
MRTN Rate, 95% of acreage in Cover Crops, 34% of ag land in heavily tile drained land treated with wetland, and 5% land retirement
42 50 1,222 1,214 58
Department of Agricultural and Biosystems Engineering
Summary• To achieve goals will require a combination of
practices – conservation systems approach• N versus P may require different practices• Multiple benefits and costs of practices need
to be considered• Iowa has initiated the Iowa Water Quality
Initiative as part of the Nutrient Reduction Strategy and has implemented a number of watershed demonstration practices
Department of Agricultural and Biosystems Engineering