Iowa Nutrient Reduction Strategy: Background Information 2013 Iowa Water Conference Reid Christianson, P.E., Ph.D. Center for Watershed Protection Ellicott City, Maryland
Project Components Project Goal 45% reduction in riverine N & P Baseline Development Best Management Practice performance Scenario Development Economic Assessment www.nutrientstrategy.iastate.edu
Steps in Baseline Development Define Scale Determine Land Use Determine Yield Nitrogen Fertilizer, manure, timing Phosphorus Application rate, soil test P, tillage
What scale? Iowa s Major Land Resource Areas (MLRA)
Land Use Development NASS Cropland Data Layer for 2006 2010
NASS Cropland Data Layer
Resulting Crop Acres MLRA CS CC EXT PH ac ac ac ac 102C 170,151 50,077 18,179 38,866 103 4,737,173 1,252,577 190,573 351,362 104 3,196,748 1,031,193 275,016 402,026 105 381,386 339,918 201,090 705,142 107A 1,833,615 208,446 95,204 118,910 107B 2,938,063 408,404 280,603 510,586 108C 2,137,445 479,204 310,546 855,004 108D 960,321 65,004 199,602 999,998 109 582,197 63,872 201,816 1,564,762 115C 127,776 44,996 20,183 31,534 Iowa Total 17,064,873 3,943,694 1,792,812 5,578,194
Corn and Soybean Yields County averages 2007 Census of Agriculture Harvested grain Harvested area Counties split between MLRAs Partitioned based on area in MLRA Corn yields proportionally adjusted based on crop area ~8% lower than observed in a corn soybean rotation (Erickson, 2008)
Resulting Yields MLRA Corn Yield Corn Soybean Corn Yield Continuous Corn Soybean Yield bu/ac bu/ac bu/ac 102C 163 150 53 103 175 161 50 104 176 162 51 105 179 165 50 107A 161 148 51 107B 156 143 49 108C 177 163 51 108D 151 139 49 109 155 143 47 115C 181 167 49
Water Yield and Tile Drainage Water Yield Long term USGS measured flow and National Climatic Data Center daily precipitation Tile drainage based on the Iowa Drainage Guide Soil series requiring drainage Slopes less than or equal to 2%
MLRA 103 104 105 107A 107B 108C 108D 109 Water Yield in/yr 10.4 11.9 11.3 7.1 8.2 11.2 9.8 12.0
N Application Considerations What was the source? What type of crop was it applied to? When was the nitrogen being applied? What was the method of application? Was it applied with an inhibitor?
Nitrogen Use This is where all the fun starts Points of substantial discussion How to credit manure? How to take into account the variability of N application? Fertilization of pasture and hay? What about urban turf grass? Significant time required to hash out these details
Nitrogen Application David et al., 2010 Manure Fertilizer Swine Poultry Cattle Subtracted turf grass Subtracted N from cattle on pasture Subtracted pasture Adjusted for first year availability Subtracted alfalfa Nitrogen applied to corn
Overall N Application Based on David et al. (2010) county estimates Adjusted for cattle on pasture (2002 Ag Census) Manure numbers adjusted for first year availability Manure Source Availability (%) Cattle 40 Broilers 60 Layers 60 Turkey 60 Hog 100 Sawyer and Mallarino (2008) Subtracted 9% of statewide nitrogen sales for turf grass (Libra et al., 2004)
N to Pasture and Alfalfa Pasture N based on recommended application rate across state 80 lb N/ac (Barnhart et al., 1997) Alfalfa N rate based on phosphorus use 4 ton/ac/yr yield (Duffy, 2011) 12.5 lb P 2 O 5 /ton (Sawyer et al., 2011) Ratio of MAP to DAP sales (IDALS, 2011) = Ratio of MAP to DAP application ~17 lb N/ac
MLRA Commercial Fertilizer Manure Total Applied to Corn lb N/ac lb N/ac lb N/ac 102C 117 84 201 103 136 35 171 104 134 29 163 105 130 33 163 107A 129 64 193 107B 128 22 149 108C 148 30 178 108D 108 18 126 109 123 28 151 115C 144 22 166 Iowa Total 133 33 166
Adjustment for Continuous Corn Assume 50 lb/ac more N applied on continuous corn (Blackmer et al., 1997; Sawyer et al., 2011c) MLRA Total Applied to Corn Rate on CB Rate on CC lb N/ac lb N/ac lb N/ac 102C 201 182 232 103 171 154 204 104 163 144 194 105 163 131 181 107A 193 184 234 107B 149 139 189 108C 178 163 213 108D 126 120 170 109 151 142 192 115C 166 146 196 Iowa Total 166 151 201
Timing and Inhibitors Timing Assumed 25% of fertilizer applied in fall (Randall and Sawyer, 2008) Assumed all manure is applied in fall Inhibitor Roughly 2 million acres treated with nitrapyrin (Dow AgroSciences, 2012) Assumed applied with fall anhydrous
P Application Considerations How much P was applied? To which crop was it applied? When was P applied? How much P is in the soil? Was it incorporated into the soil? What is the distance to a stream?
P Application Based on Jacobson et al. (2011) county estimates Adjusted for cattle on pasture (2002 Ag Census) Total P partitioned to corn, soybeans, and hay Based on fraction of P used by each crop (Sawyer et al. 2002) P removal in soybean and corn grain was 0.8 lb P 2 O 5 /bu 0.375 lb P 2 O 5 /bu, respectively P removal in alfalfa was 12.5 lb P 2 O 5 /ton For Example : 1. 0.8 lb P 2 O 5 /bu removal by SB x total soybean bu in a given county 2. Sum total P removed by SB, C, and alfalfa in that county to get % removed by each crop 3. Multiply these percentages by the Jacobson et al. application value
Resulting P Application MLRA Rate on Corn Rate on Rate on Alfalfa Soybean Hay lb P 2 O 5 /ac lb P 2 O 5 /ac lb P 2 O 5 /ac 103 59 35 34 104 56 35 40 105 64 42 51 107A 81 53 55 107B 48 31 32 108C 58 38 39 108D 44 29 28 109 54 36 32 Iowa Total 58 37 38
Soil Test P Soil samples analyzed by the ISU Soil and Plant Analysis Laboratory (2006 to 2010) (Mallarino et al., 2011) Highest county 131 ppm Optimum 16 to 20 ppm MLRA Soil Test P (ppm) 103 30 104 27 105 27 107A 32 107B 28 108C 27 108D 19 109 11
Tillage Estimates from the Conservation Technology Information Center (CTIC) Conservation Tillage (>30% residue) No till/ridge Till Mulch Till No Till Mulch Till No Till Mulch Till MLRA % of CC % of CC % of CS % of CS 102C 4 16 11 25 103 4 34 9 49 104 11 37 24 38 105 11 30 31 37 107A 8 21 14 40 107B 39 24 53 21 108C 15 31 36 28 108D 28 28 45 24 109 11 21 34 24 115C 9 37 33 29
Distance Classes & Soils Information Iowa P Index Data Requirements Distance from center of field to National Hydrography Dataset streams 7 distance classes (0 500, 500 1,000, 1,000 2,000, 2,000 4,000, 4,000 8,000, 8,000 16,000, and >16,000 feet) Representative soil type for each distance class Erodibility factor, saturated hydraulic conductivity, slope, slope length Zonal statistics to estimate mean values Land cover determined RUSLE cover factor
Future Efforts Data Collection Fertilizer sales by county with intended county of application? Incentivized self reporting? Could include information on N & P use, crop area, yield, etc. Poll Co ops for anonymous pertinent information?
Summary Component Land Use Water Yield Tile Drainage Source NASS Cropland Data Layer National Climatic Data Center, USGS Water Watch Iowa Drainage Guide, Soil Survey Geographic (SSURGO) Database Nitrogen Application David et al. (2010), USDA Census of Agriculture, Libra et al. (2004), Sawyer and Mallarino (2008), Barnhart et al. (1997), Duffy (2011), Sawyer et al. (2011), IDALS (2011) Phosphorus Application Soil Test P Mallarino et al. (2011) Tillage CTIC (2004) Jacobson et al. (2011), USDA Census of Agriculture, Sawyer et al. (2002) Iowa P Index Input Soil Survey Geographic (SSURGO) Database, SCS Iowa (1990), National Land Cover Database (NLCD), National Hydrography Dataset (NHD)
Continuous Corn and Corn Soybean Corn Yield Adjustments Corn yields for continuous corn ~8% lower than observed in a corn soybean rotation (Erickson, 2008) Corn yields proportionally adjusted based on crop area Up for corn in a corn soybean rotation Down for continuous corn Overall corn yield matches MLRA average
Contour Farming and Terraces Available datasets are incomplete mainly for farm programs Used best professional judgment on MLRAs where practice would likely be prevalent Contour farming on 50% of land in MLRA 105 Combination of contour farming and terraces on 50% of land in MLRA 107B