Filosofía de la Recomendación en Fertilización de Cultivos


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Filosofía de la Recomendación en Fertilización de Cultivos

  1. 1. Fertilizer Recommendation Philosophies Richard B. Ferguson University of Nebraska
  2. 2. Fertilizer Recommendation Philosophies Philosophy - style of management. Relates to what type of risk the producer is most comfortable with. Applies to non-mobile nutrients, primarily phosphorus and potassium, to a lesser extent calcium and magnesium.
  3. 3. Soil pH Levels Percent testing 6.0 or less. Source: P.E. Fixen - Potash Phosphate Institute Better Crops, No. 4, 1998
  4. 4. Soil Test P Levels Percent testing medium or lower. Source: P.E. Fixen - Potash Phosphate Institute Better Crops, No. 4, 1998
  5. 5. Soil Test K Levels Percent testing medium or lower. Source: P.E. Fixen - Potash Phosphate Institute Better Crops, No. 4, 1998
  6. 6. What is a “Medium” soil test level? What is a “Critical Level”? 15 ppm pm m “Medium” test is p rn: 12 pp 25 Co an: at: e relatively meaningless. yb he So W UNL Categories VH “Critical Level”- is the Test Category H soil test value above which fertilizer is not M recommended because there is not a L significant likelihood VL of yield increase. The 0 5 10 15 20 25 30 35 40 45 50 value depends on the Bray-1 P (ppm) crop.
  7. 7. Fertilizer Recommendation Philosophies Deficiency Correction Nutrient Removal Maintenance Build Cation Balance
  8. 8. Soil Tests - Are an index - they estimate plant availability of nutrients under field conditions – not the total amount of nutrient in the soil.
  9. 9. Types of Risk - Fertilizer Application Deficiency Correction - Intended to optimize profit. The risk is that in some years, or some locations within fields, nutrient supply may limit yield. Maintenance - Intended to minimize potential for nutrient limitations to yield. The risk is that, in most years, no yield increase will occur with the last increments of fertilizer, thus reducing profit, and that environmentally excessive rates may be applied in some locations of the field.
  10. 10. Question: Should fertilizer be applied at rates adequate to take advantage of higher yield potential in years with exceptional climatic conditions?
  11. 11. Answer: In most cases, when climatic conditions favor exceptional yields, they also favor above-average availability of soil-derived nutrients. Consequently there is no need to fertilize above calibrated rates in order to realize full yield potential in exceptional years.
  12. 12. NSFP 2002 – Yield Response to Selected Treatments 300 5 5 9 9 11 11 12 12 12 12 13 13 14 14 17 17 20 20 20 20 49 49 74 Bray-1 P 74 Bray-1 P (ppm) (ppm) 250 200 150 N2P0K1 N2P0K1 100 N2P1K1 N2P1K1 N4P2K2 N4P2K2 50 UNL UNL 0 d d er k C fff e o on e d EC d d r ay ick EC ce Be irro on e d EC uf Sc ntte ic oo orr orr RE ea nc oo ea lu i o o an R xtt CR Ca n sw bl CR Ca sw ym nc x w ym nc sb M lliia llllw SC Ce M SC Ce Pa Pa tts W un Co W All un Co W A ott W Be o ay Br Br Sc Cl Cl
  13. 13. Fertilizing the Crop Fertilizing the Soil
  14. 14. Fertilizing the Soil Soil is a very inefficient location to store fertilizer. Crop recovery of fertilizer P, for example, is typically less than 30% in the year of application, and less than 10% the following year. Fertilizer orthophosphate is converted to increasingly less soluble forms of calcium phosphate with time, reducing the availability of applied P to plants.
  15. 15. Deficiency Correction Results from research on crop response to additions of a nutrient otherwise insufficient for maximum growth. Relies on correlation and calibration field research. Goal of applying fertilizer P or K to optimize economic return in the year of application.
  16. 16. Soil Test Research Correlation - Determination of crop yield at different soil test levels for a given nutrient. Calibration - How much fertilizer is required to optimize yield at different soil test levels.
  17. 17. Maintenance & Build Maintenance implies that maintaining a soil test level at or above the point of economic maximum yield benefits the producer over time. Build implies that fertilizer added beyond crop removal rates to increase soil test levels over time will be beneficial. The most likely use for this approach is when soil nutrient levels are very low and long-term land tenure is assured.
  18. 18. Maintenance & Build Assume approximately 18 lb/acre of P2O5 is required to raise Bray-1 P test 1 ppm; 24-27 lb/acre to raise Olsen P test 1 ppm. Assume 9-10 lb/acre K2O is required to increase soil K test 1 ppm.
  19. 19. Yield Response as Influenced by Soil Test Level Yield Response as Influenced by Soil Test Level and Recommendation Philosophy and Recommendation Philosophy Economic Maximum Yield 100 75 Critical Level % Yield 50 25 Deficiency Correction Maintenance/ crop removal Maintenance & Build 0 VL L M H VH Soil Test Level
  20. 20. Crop Removal Ultimately, over the long-term, both deficiency correction and maintenance & build recommendation programs will gravitate towards replacing the nutrients removed in yield. Fertilization according to crop nutrient removal is not likely to be as profitable as deficiency correction in the short-term. Land tenure is a major factor influencing one’s choice of fertilizer program.
  21. 21. Cation Balance Suggests there is an optimum ratio of basic cations and that there is a best total base saturation for each soil. “Ideal” ratio: Ca - 65%, Mg - 10%, K - 5%, H - 20%. Initially developed in New Jersey, further researched in Missouri.
  22. 22. Cations required to increase saturation of exchangeable Ca, Mg and K to the mid-point of a desired range. Soil CEC = 15 meq/100 g Soil pH: 5.6 Actual Saturation Desired Desired Nutrient meq/100 g (%) Saturation meq/100 g Required (%) 4.3 Ca 6.00 40.0 75.0 11.25 tons/acre ag-lime Mg 1.50 10.0 10.0 1.50 None 390 lb/acre K 0.24 1.6 3.5 0.53 0-0-60
  23. 23. Cation Balance Soils have been shown to have wide ranges of cation ratios and still be highly productive. Approach has no validity for soils with pH’s above 7, but is often used for recommending K and Mg anyway.
  24. 24. How do different philosophies, or strategies, of fertilizer recommendation compare in yield or profitability?
  25. 25. University of Nebraska Comparison Study Primary objective - To scientifically compare fertilizer recommendation strategies for a range of Nebraska soils. Conducted at five locations across the state - continued for up to 10 years at each location.
  26. 26. UNL Comparison Study Location North Platte Clay Center Mead Concord Yield 170 bu/a 170 – 200 bu/a 170 bu/a 90 bu/a Goal Corn Corn Corn Corn Strategy MB DC MB DC MB DC MB DC Fertilizer $/acre 54 26 56 30 62 35 27 12 Yield Bu/acre 167 167 186 189 152 154 83 84 MB - Maintenance + Build. DC - Deficiency Correction. Average cost and yield over 7 years.
  27. 27. “The University of Nebraska didn’t recommend any phosphorus for my field, and yet I had a 15 bushel per acre yield increase when I applied 50 lb per acre on the east half, compared to the west half where I applied only nitrogen.”
  28. 28. Why? Spatial variability of nutrient levels, combined with inadequate soil sampling, may be a major factor in differences in perception of fertilizer recommendations. Personal observation or testimonials may not reflect valid comparisons.
  29. 29. Treatment Comparison Split-field designs to compare treatments are basically invalid. There is no way to measure random error. Comparison of treatments must occur in a replicated, randomized manner.
  30. 30. Summary Recommendation philosophies, or strategies, apply primarily to P and K in Nebraska, to a lesser extent Ca, Mg, S and micronutrients. The type of risk the producer is most comfortable with will influence his fertilizer management strategy. The deficiency correction approach has been shown through research to have the greatest short- term profitability in Nebraska.
  31. 31. Exercise P2O5/acre 2 5 Deficiency Crop Bray P bu/a Correction Removal For the 11 yr. period shown, For the 11 yr. period shown, 12 2002 245 calculate the annual recommended calculate the annual recommended P22O55/acre rates using two P O /acre rates using two 2003 252 approaches: deficiency correction approaches: deficiency correction and crop removal. Calculate the 2004 215 and crop removal. Calculate the total P22O55 applied, the average total P O applied, the average 2005 196 annual rate, and the total fertilizer annual rate, and the total fertilizer cost over the 11 year period. cost over the 11 year period. 9 2005 205 Assume crop removal to be 0.33 Assume crop removal to be 0.33 lb P22O55/bu. lb P O /bu. 2007 188 2008 243 2009 216 5 2010 199 2011 238 2012 224 Total P2O5 Total P2O5 Annual mean Annual mean P cost (@ $.30/lb) P cost (@ $.30/lb)
  32. 32. Exercise Bray P bu/a P2O5/a DC CR 12 2002 245 40 81 2003 252 40 83 2004 215 40 80 2005 196 40 65 9 2005 205 40 68 2007 188 40 62 2008 243 40 80 2009 216 40 71 5 2010 199 80 66 2011 238 80 79 2012 224 80 74 Total P 560 809 Annual mean 51 74 P cost (@ $.30/lb) $168 $243