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History of Phosphorus in North Carolina

This article discusses the history of phosphorus in North Carolina soils, including its initial low levels and subsequent buildup through cultivation. It explores the different forms of phosphorus in soils, the critical levels required for optimal crop yield, and the effect of clay content on phosphorus loss. The article also highlights the use of the Mehlich 3 extractant and the importance of historical research and data in making informed decisions about phosphorus management today.

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History of Phosphorus in North Carolina

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  1. SERA 6 Meeting June 20, 2011 History of Phosphorus in North Carolina Dr. Eugene Kamprath Professor Emeritus North Carolina Statue University

  2. North Carolina Soils Mountain, Piedmont, Coastal Plain

  3. Norfolk- Coastal Plain Soil fine-loamy, kaolinitic, thermic Typic Kandiudult Cecil / Georgeville- Piedmont Soils fine, kaolinitic, thermic Typic Kanhapludult

  4. Phosphorus • Soils initially low in P • Cultivated soils – buildup of P • Piedmont soils • High buffer capacity • Coastal plain soils • Low buffer capacity

  5. Forms of P in NC Soils

  6. Yield (%) of Check Plots Compared to Fertilized Plots related to STP

  7. Corn Yield Increase to 22 lbs P / acre- Coastal Plain Soils

  8. P32 Studies with Corn P rate = 18 lbs / acre banded Nelson et al., 1948

  9. Effect of Anion on P Extraction Seatz, 1949, Ph.D Thesis, NCSU

  10. Mehlich 1 (Double Acid) • 0.05 N HCl + 0.025 N H2SO4 • Addition of SO4 increased extraction of P from Al and FePO4 • (Seatz 1949 Ph.D. thesis- NCSU) • Suitable for soils in the southeastern US • Introduced in 1949

  11. Critical M1P Levels for Cecil and Norfolk Soils

  12. Critical M1P for Coastal Plain, Piedmont, and Mountain Soils

  13. P Rate Needed to Change M1Pas Influenced by Clay

  14. Critical M1P Level 3 Piedmont Ultisols

  15. Piedmont – P Relationships • Al-P converted to Fe-P, rapid rate first 3 years after application • M1-P highly correlated with Al-P • Rapid decrease in M1-P first 2 years after application, followed by much slower rate of decrease • M1-P critical level for wheat, 8 – 10 ppm Shelton, 1960 Ph.D Thesis, NCSU Shelton & Coleman, 1960

  16. Residual P – Georgeville Soil Kamprath, 1967

  17. Tidewater Research Station

  18. P Management on Portsmouth Soil • M1-P critical level for corn / soybean, 22 ppm • Long term study 1955 – 1985 • Annual band application of 16 kg/ ha (equal to P removal in grain) maintained critical level • No yield advantage to keeping soil test above critical level • M1-P of 100 ppm supplies adequate P for 14 – 16 yrs. McCollum, 1991

  19. Effect of P Application on Soil Solution P

  20. Effect of P Application on Soil Solution P

  21. 100 % Phosphorus Saturation

  22. Change in M1P in 3 Ulitsols14-Year Cropping with 0 P Applied

  23. Effect of P Rate on M1P

  24. Effect of P Rate on M1P

  25. Mehlich 3 Extractant • NH4F, HOAc, NH4NO3, HNO3, EDTA • pH 2.5 • Introduced in 1981 • Extracts 1.5 – 2 times more P than M1P

  26. Critical Levels Coastal Plain • Greenhouse millet • Norfolk M1P = 31 ppm • Field • Portsmouth corn M1P = 22 ppm • Norfolk corn M1P = 25 ppm M3P = 55 ppm • Portsmouth corn M3P = 43 ppm wheat M3P = 64 ppm soybean M3P = 50 ppm • Goldsboro soybean M3P = 40 ppm

  27. Critical Levels Piedmont • Greenhouse millet • Cecil M1P = 16 ppm • Cecil, Davidson, Georgeville M1P = 12 ppm • Field • Davidson, corn & soybean • M1P = 6 – 8 ppm M3P = 10 – 13 ppm • Georgeville • Corn M1P = 8 ppm • Wheat M1P = 8 ppm

  28. P Management • CP soil with initial M1P of 105 ppm after 14 years cropping had M1P of 60 ppm & M3P of 120 ppm – high soil test P • CP soil with initial M1P of 50 ppm supplied adequate P for 13 years, 17 kg P/ha/yr harvested • Piedmont soil with initial M1P of 10 ppm supplied adequate P for 12 years • Annual P rate of 20 kg P/ha maintains critical level

  29. M3P Soil Test Levels over Time

  30. Effect of Clay Content on M3P

  31. P Loss Assessment Tool (PLAT) • Environmental regulation and P loss today • Mehlich 3 P now used as an input for this • Historical research and data important in making decisions about PLAT and P management today

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