Dr. Jim Camberato - Nitrogen Management: We Aren't There Yet
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Nitrogen Management: We Aren't There Yet - Dr. Jim Camberato, Purdue University, from the 2020 Conservation Tillage and Technology Conference, held March 3-4, 2020, Ada, OH, USA.
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Dr. Jim Camberato - Nitrogen Management: We Aren't There Yet
- 1. James J. Camberato www.soilfertility.info jcambera@purdue.edu Nitrogen management – we aren’t there yet
- 2. Objective of better N management •Choose a combination of source, placement, timing, and rate of N application that minimizes the amount of unused N and its susceptibility to loss while optimizing profit
- 3. Yield-based N rec. for corn was the standard up until 10 years ago, it was suggested first in 1966 (G. Stanford, USDA-Beltsville, Md.) Fertilizer N recommendation = (Yield x N factor at harvest - soil N contributed) / efficiency of fertilizer use) Nitrogen recommendation models use the same approach
- 4. Crop N requirement is the target •Based on expected yield x the concentration of N in the above-ground plant at physiological maturity (expressed on a bushel of grain basis)
- 5. Stanford, N factor •Yield target (bu/ac) x plant N concentration (1.2 lb N/bu) •Based on experiments conducted from 1946 through 1960 in GA, MS – 3 years each; NE – 4 and 2 years at 2 locations
- 6. Tri-state yield goal approach •N (lb/acre) = -27 + (1.36 x yield potential) – N credit (30 lb N/acre following soybean) •Soil contribution is 57 lb N/acre •N factor is 1.36 •No fertilizer efficiency factor
- 7. Predictions needed for an accurate yield- based N recommendation •Accurate prediction of: •Crop yield •Plant N content associated with crop yield •Soil N mineralized •Fertilizer lost (efficiency of fertilizer use)
- 8. 29* 45 28 54 Yield range (bu/acre) within each field over 5 corn years in C/S rotation
- 9. An example of modeled yield vs achieved yield at ACRE and PPAC Across 33 site-years of data at ACRE and PPAC maximum yield was predicted at 201 bu/acre vs actual yield of 204 bu/acre
- 10. What is the correct pounds of N per bushel number? lbs. N per bushel Yield Goal Plant N at harvest Least effic. 1.20 200 240 Most effic. 0.77 200 154 Avg. 0.93 200 187 Shafer, 2016
- 11. Variation in crop N requirement •Assuming yield was predictable, the N factor varied enough to change the crop N requirement 85 pounds per acre •Variation in the N factor was not related to easily measured variables including soil properties and weather
- 12. Mineralization of soil N •Soil N – microbial release of N from soil organic matter, microbial biomass, and crop residues. Perhaps release of ammonium (NH4 +) form the interlayer of 2:1 clay minerals •Soil N can contribute a significant portion of the N accumulated by the crop in some soils •Substantial differences can arise from year to year in soil N contribution
- 13. Grain yield/acre on average equal to pounds of N/acre 101Indianatrials,cornaftersoybean GrainyieldwithoutfertilizerN
- 14. Microbial respiration test correlates well in 1 of 3 years to Economic Optimum N Rate (EONR) Bean et al., 2020, unpublished data CO2-C, ppm 0 270 225 180 135 90 45 EONR,lb/acre
- 15. Carbon dioxide release (4-d) as a measure of potential microbial activity and N mineralization was related to EONR, but only weakly across 49 site-years Bean et al., 2020, unpublished data CO2-C, ppm EONR,lb/acre 0 270 225 180 135 90 45
- 16. ACRE Nitrogen mineralization •Fields – 6 locations with corn/soybean rotation for 10 years with N rates varying from 25 to 280 lb N/acre/year • N uptake by corn fertilized with ~25 lb N/acre as 2x2 starter was used to assess soil N mineralization in 2015 season •Laboratory - N mineralization potential was determined under temp. and moisture conditions typical for expt. areas
- 17. Field evaluation Crop N content at maturity with starter- only Moser, 2016 4.0% 3.6% 2.9% 4.1% 2.8% 2.7% TotalplantNatR6(lbacre-1) 0 27 54 81 O.M.
- 18. Laboratory incubation N release after 50 days under ideal temp. and moisture Moser, 2016 4.0% 3.6% 2.9% 4.1% 2.8% 2.7% TotalinorganicN(mgkg-1) 0 50 100 150 200 250 300 O.M.
- 20. Nitrogen mineralization decreases above and below field capacity 0 10 20 30 40 50 60 70 80 0 5 10 15 20 25 30 35 40 MineralizedN(mg/kg) Soil Water (g/g) * 10 kPa 200 kPa Idaho Silt Loam Adapted from Stanford and Epstein (1974) Field cap. MineralizedN,ppm
- 21. Yields with starter- only were greater in soils with better internal drainage Location Moser, 2016 143--- 112--- 80--- 48--- 16--- Starter-onlygrainyield,bu/acre Ksat (μm s-1)
- 22. Yield and excess water Moser, 2016 R² = 0.70 R² = 0.43 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 50 100 150 200 250 300 350 400 450 Yield(kg/ha) Excess Water (mm) DPAC ACRE TPAC R² = 0.83 Ksat (μm/s) 3.1 8.6 9.6 143--- 112--- 80--- 48--- 16--- Starter-onlygrainyield,bu/acre 0 2 4 6 8 10 12 14 16 18
- 23. Estimates of N mineralization •Need to incorporate weather (actual, forecast, and historical) and soil properties into prediction (especially topography and artificial drainage that modify the natural drainage characteristics of the soil)
- 24. Water table adjusted available water holding capacity useful to predict EONR 41% variation in EONR explained with AWC Adding rainfall to AWC explains 47% EONR Qinetal.,2018,AJ110:1-12.
- 26. • Field scale trials – 10-50+ acres • 7 Purdue farms and many farmer fields • 5-6 N rates replicated 4-6 times A database of N responses was used to create N rate recommendations
- 28. Regional study to evaluate N rec. systems • N response trials • 2014-2016 • 8 states • 2 sites/state • 49 site-years total Kitchen et al., 2017, AJ 109:2371-2388. Support from:
- 29. Treatments and determination of EONR • 8 N rates of 0-280 lb N/acre in increments of 40 lb N/acre • Broadcast-applied at planting or at V9 Ransom et al., 2020, AJ 112:470-492. 0 256 192 128 64 Grainyield,bushels/acre N application, pounds/acre 0 2702251801359045 36 0 252 216 180 144 108 72 Est.totalseasonNloss,pounds/acre
- 30. Nitrogen recommendations tested • Yield-goal • MRTN • Pre-sidedress nitrate test • Active optical sensor • Plant growth model • Farmer’s choice • Soil properties • Weather • Soil moisture • Plant N uptake
- 31. 0 10 20 30 40 50 60 70 80 27 27-54 54 %ofsitesineachcategory YG MRTN PSNT Farmer Model Sensor ± ± >± Difference between pred. actual EONR, pounds per acre Ransom et al., 2020, AJ 112:470-492.*only 36 site years had MRTN recommendations * Some rec. tools were better than others
- 32. Model Yieldgoal Sensor PSNT Farmer MRTN Sensor PSNT Model Yieldgoal Farmer MRTN Sensor PSNT The best tools for recommendations minimize environmental costs relative to the true EONR -270 -225 -180 -135 -90 -45 0 LossrelativetotrueEONR,$/acre 66 22 0 22 66 110 154 168EnvironmentalcostrelativetotrueEONR,$/acre Ransom et al., 2020, AJ 112:470-492.
- 33. Additional approaches to recommendations •How can these tools be combined to improve recommendations •Weather variables improved sensor and anaerobic mineralizable N predictions of EONR •PSNT improved mineralizable N predictions of EONR •Etc.
- 34. "It is a riddle, wrapped in a mystery, inside an enigma.“ Sir Winston Churchill
- 35. Summary •Yield-goal based and model-driven N recommendation systems attempt to estimate N requirement by predicting •(yield per acre x total plant N content per bushel of grain anticipated minus soil N) / an efficiency factor
- 36. Yield •The range in yield from an available N recommendation model varied 50 bu/acre, sometimes high sometimes low •All other things being equal the N requirement based on yield can vary by approximately 50 lb N/acre
- 37. Nitrogen content per bushel •Assuming yield is predicted accurately and all other things are equal •Variation in plant N content per bushel at the optimum N rate can vary as much as ~0.45 lb N per bushel which would result in a 90 lb N per acre variation in plant N content at a yield of 200 bu per acre
- 38. Soil N mineralization •Soil N mineralization can provide little to all of the N accumulated by the crop at physiological maturity •In a particular field year-to-year variability ranged from 40 to 100 lb N acre-1
- 39. Conclusion •Variation in currently difficult to predict factors suggest that static yield-goal based N recommendations systems can at best estimate fertilizer N requirement no better than 40-50 lb N/acre in Indiana systems which is no better than experimentally-derived N recommendations •Models should be thoroughly tested with existing data to evaluate whether or not they can do better
- 40. Using weather up to the time of sidedressing and soil clay content improved prediction made by active optical sensor
- 41. Comparison of MRTN to a mechanistic model N recommendation across 22 Indiana C/S locations
- 42. Corn Belt rainfall similar during the growing season, but lesser in the Eastern Corn Belt off- season
- 43. No/weak relationship between N fertilizer needed and yield achieved 250 site-years, IN
- 44. Regional N management project 16 locations across 8 states 2014-2016 Nitrogen rates 0 to 280 lb N ac-1 in 40 lb N ac-1 increments, all at planting or 40 lb N ac-1 at-planting and the remainder at V9. Hybrids Several used based on location Support from:
- 45. Variation in IE@EONR across 30 sites resulted in ~90 lb N/a range in plant N Bushel per lbs. N lbs. N per bushel Yield Goal Plant N at harvest Least effic. 0.83 1.20 200 240 Most effic. 1.30 0.77 200 154 Avg. 1.07 0.93 200 187 Shafer, 2016
- 46. Corn is less efficient at higher N rates in producing grain per unit of N content Shafer, 2016
- 47. Determine EONR for each location EONR Shafer, 2016
- 48. Shafer, 2016 Efficiency at the optimum is key
- 49. IE@EONR was related to plant N content at VT when no fertilizer was applied – soil N supplying capacity Shafer, 2016
- 50. EconomicoptimumNrate,lb/acre 0 315 270 225 180 135 90 45 360 0 8642 Water table adj. avail. water capacity, inches Can be modified
- 51. Yield and excess water 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 50 100 150 200 250 300 350 400 450 Yield(kg/ha) Excess Water (mm) SEPAC PPAC NEPAC Ksat (μm/s) 8.0 14.1 8.6 143--- 112--- 80--- 48--- 16--- Starter-onlygrainyield,bu/acre Moser, 2016