Iowa Nutrient Reduction Strategy: Background Information

Transcription

1 Iowa Nutrient Reduction Strategy: Background Information 2013 Iowa Water Conference Reid Christianson, P.E., Ph.D. Center for Watershed Protection Ellicott City, Maryland

2 Project Components Project Goal 45% reduction in riverine N & P Baseline Development Best Management Practice performance Scenario Development Economic Assessment

3 Steps in Baseline Development Define Scale Determine Land Use Determine Yield Nitrogen Fertilizer, manure, timing Phosphorus Application rate, soil test P, tillage

4 What scale? Iowa s Major Land Resource Areas (MLRA)

5 Land Use Development NASS Cropland Data Layer for

6 NASS Cropland Data Layer

7 Resulting Crop Acres MLRA CS CC EXT PH ac ac ac ac 102C 170,151 50,077 18,179 38, ,737,173 1,252, , , ,196,748 1,031, , , , , , , A 1,833, ,446 95, , B 2,938, , , , C 2,137, , , , D 960,321 65, , , ,197 63, ,816 1,564, C 127,776 44,996 20,183 31,534 Iowa Total 17,064,873 3,943,694 1,792,812 5,578,194

8 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)

9 Resulting Yields MLRA Corn Yield Corn Soybean Corn Yield Continuous Corn Soybean Yield bu/ac bu/ac bu/ac 102C A B C D C

10 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%

11 MLRA A 107B 108C 108D 109 Water Yield in/yr

12 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?

13 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

14 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

15 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)

16 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

17 MLRA Commercial Fertilizer Manure Total Applied to Corn lb N/ac lb N/ac lb N/ac 102C A B C D C Iowa Total

18 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 A B C D C Iowa Total

19 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

20 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?

21 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 lb P 2 O 5 /bu, respectively P removal in alfalfa was 12.5 lb P 2 O 5 /ton For Example : 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

22 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 A B C D Iowa Total

23 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) A B C D

24 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 A B C D C

25 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

26 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?

27 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)

28 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

29 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