1. Iowa Nutrient Reduction Strategy: Background Information 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. Project Team Science Team – ~20 individuals – Representing 5 agencies or organizations – Three subgroups Nitrogen Phosphorus Hydrology

5. What scale should be used? Discussion on the appropriate scale of analysis – Field? – Township? – County? – Major Land Resource Area (MLRA)? Discussion on data sources available – USDA-NRCS Comprehensive Effects Assessment Project (CEAP)?

6. Iowa’s Major Land Resource Areas (MLRA)

7. Land Use Development NASS Cropland Data Layer for 2006 – 2010

8. NASS Cropland Data Layer

9. MLRACSCCEXTPH ac 102C 170,15150,07718,17938,866 103 4,737,1731,252,577190,573351,362 104 3,196,7481,031,193275,016402,026 105 381,386339,918201,090705,142 107A 1,833,615208,44695,204118,910 107B 2,938,063408,404280,603510,586 108C 2,137,445479,204310,546855,004 108D 960,32165,004199,602999,998 109 582,19763,872201,8161,564,762 115C 127,77644,99620,18331,534 Iowa Total 17,064,8733,943,6941,792,8125,578,194 Resulting Crop Acres

10. Corn and Soybean Yields County averages – 2007 Census of Agriculture Harvested grain Harvested area Counties split between MLRAs – Partitioned based on area in MLRA

11. 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

12. Resulting Yields MLRA Corn Yield Corn-Soybean Corn Yield Continuous Corn Soybean Yield bu/ac 102C 163150 53 103 175161 50 104 176162 51 105 179165 50 107A 161148 51 107B 156143 49 108C 177163 51 108D 151139 49 109 155143 47 115C 181167 49

13. 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%

14. MLRAWater Yield in/yr 10310.4 10411.9 10511.3 107A7.1 107B8.2 108C11.2 108D9.8 10912.0

15. Nitrogen Use This is where all the fun starts Point 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

16. N Components 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?

17. Nitrogen Application David et al., 2010 ManureFertilizer SwinePoultryCattle Subtracted N from cattle on pasture Adjusted for first year availability Subtracted turf grass Subtracted pasture Subtracted alfalfa Nitrogen applied to corn

18. 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 Subtracted 9% of statewide nitrogen sales for turf grass (Libra et al., 2004) Manure SourceAvailability (%) Cattle40 Broilers60 Layers60 Turkey60 Hog100 Sawyer and Mallarino (2008)

19. 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

20. MLRACommercial FertilizerManureTotal Applied to Corn lb N/ac 102C11784201 10313635171 10413429163 10513033163 107A12964193 107B12822149 108C14830178 108D10818126 10912328151 115C14422166 Iowa Total13333166

21. 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 CornRate on CBRate on CC lb N/ac 102C201182232 103171154204 104163144194 105163131181 107A193184234 107B149139189 108C178163213 108D126120170 109151142192 115C166146196 Iowa Total166151201

22. 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

23. P Components 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?

24. 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

25. Resulting P Application MLRA Rate on Corn Rate on Soybean Rate on Alfalfa Hay lb P 2 O 5 /ac 103 593534 104 563540 105 644251 107A 815355 107B 483132 108C 583839 108D 442928 109 543632 Iowa Total583738

26. 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 MLRASoil-Test P (ppm) 10330 10427 10527 107A32 107B28 108C27 108D19 10911

27. Tillage Estimates from the Conservation Technology Information Center (CTIC) – Conservation Tillage (>30% residue) No-till/Ridge-Till Mulch-Till No-TillMulch TillNo-TillMulch Till MLRA% of CC % of CS 102C4161125 103434949 10411372438 10511303137 107A8211440 107B39245321 108C15313628 108D28 4524 10911213424 115C9373329

28. 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

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

30. 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?

31. Summary ComponentSource Land UseNASS Cropland Data Layer Water YieldNational Climatic Data Center, USGS Water Watch Tile DrainageIowa Drainage Guide, Soil Survey Geographic (SSURGO) Database Nitrogen ApplicationDavid 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 ApplicationJacobson et al. (2011), USDA Census of Agriculture, Sawyer et al. (2002) Soil Test PMallarino et al. (2011) TillageCTIC (2008) Iowa P-Index InputSoil Survey Geographic (SSURGO) Database, SCS-Iowa (1990), National Land Cover Database (NLCD), National Hydrography Dataset (NHD)