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CEC effects on turf soil fertility management nov 30 2011

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Effects of Soil CEC on Turf

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CEC effects on turf soil fertility management nov 30 2011

  1. 1. CEC Effects on Turf Soil Fertility Management Byron Vaughan, Ph.D.
  2. 2. Key Discussion Points <ul><li>What is CEC </li></ul><ul><li>How CEC is determined </li></ul><ul><li>Factors affecting CEC </li></ul><ul><li>Fertility recommendations based on CEC </li></ul><ul><li>Soil acidification to improve nutrient availability </li></ul>
  3. 3. The Words Ca t ions and Anions <ul><li>English physicist and chemist Michael Faraday introduced the words anion for a negatively charged ion, and cation a for positively charged one in 1834. In Faraday's nomenclature, cations were named because they were attracted to the cathode in a galvanic device and anions were named due to their attraction to the anode. </li></ul>
  4. 4. Ca t ion Exchange Capacity <ul><li>Ca t ion – common positive charged soil nutrients </li></ul><ul><ul><li>Potassium (K +) </li></ul></ul><ul><ul><li>Ammonium (NH 4 +) </li></ul></ul><ul><ul><li>Sodium (Na +) </li></ul></ul><ul><ul><li>Magnesium (Mg ++) </li></ul></ul><ul><ul><li>Calcium (Ca ++) </li></ul></ul><ul><ul><li>Zinc (Zn +) </li></ul></ul><ul><ul><li>Manganese (Mn ++) </li></ul></ul><ul><ul><li>Iron (Fe ++) </li></ul></ul><ul><ul><li>Copper (Cu +) </li></ul></ul><ul><ul><li>Acidity (H + ) </li></ul></ul><ul><li>Anion – common negatively charged soil nutrients </li></ul><ul><ul><li>Nitrate (NO 3 - ) </li></ul></ul><ul><ul><li>Phosphate (H 2 PO 4 - )* </li></ul></ul><ul><ul><li>Sulfate (SO 4 -- ) </li></ul></ul><ul><ul><li>Chloride (Cl - ) </li></ul></ul><ul><ul><li>Borate (BO 3 - ) </li></ul></ul><ul><ul><li>Molybdate (MoO 4 - -) </li></ul></ul><ul><ul><li>Alkalinity Bicarbonate (HCO 3 - ) </li></ul></ul><ul><ul><li>*non mobile </li></ul></ul>
  5. 5. + - - + + - + - N S N S S N N S Like poles (charges) repel Opposite poles (charges) attract SOIL COLLOID Ca 2+ K + Na + Mg 2+ SO 4 2- NO 3 - Cl - NH 4 +
  6. 6. Sources and Types of Soil Negative Charges <ul><li>Sources </li></ul><ul><li>Clay </li></ul><ul><li>Organic Matter </li></ul><ul><li>Types of Charges </li></ul><ul><li>pH dependent – CEC increases with higher pH </li></ul><ul><li>Soil CEC could be expected to increase up to 100% if the pH was changed from 4.0 to 6.5 and nearly double if the pH increased from 4.0 to 8.0. </li></ul><ul><li>pH independent – pH has no effect on soil pH </li></ul>
  7. 7. Typical CEC of Soils and Soil Components
  8. 8. Typical Soil CEC Values
  9. 9. Common CEC Range Heavy Clay 50 CEC Sand 2 CEC CEC 25 More Clay, More Positions to Hold Cations CEC 5 Less Clay, Fewer Positions to Hold Cations K + Ca 2+ Mg 2+ NH 4 + Na + K + Ca 2+ K + Sand Clay
  10. 10. Measurement of CEC <ul><li>Direct – saturate soil with ammonium and then measure the amount of ammonium retained. </li></ul><ul><li>Indirect – measure the amount of extractable Ca, Mg, K, Na, and H. </li></ul><ul><ul><li>CEC = Ca ppm/200 + Mg ppm/120 + K ppm/390 + [12 x (7-BpH)] </li></ul></ul><ul><ul><li>Assumes all cations are on the exchange sites </li></ul></ul><ul><li>Estimation </li></ul><ul><ul><li>CEC = OM% x 2 + Clay% x 0.50 </li></ul></ul><ul><ul><li>Assumes a mixture of clays types which are good estimates for young soils (high pH and low rainfall) </li></ul></ul>
  11. 11. Cation Affinity for Negative sites <ul><li>Generally ions with higher valency will exchange for those of lower valency. Al +++ > Ca ++ > Mg ++ > K + = NH 4 + > Na + </li></ul><ul><li>For ions of same charge, the cation with the smallest hydrated radius is more strongly absorbed because it moves close to the site of charge. </li></ul><ul><li>Relative amount – high concentration of Na can replace Ca </li></ul>
  12. 12. Flocculating Power of Cations Cations in water attract water molecules because of their charge, and become hydrated. Cations with a single charge and large hydrated radii are the poorest flocculators. 0.96 1.08 0.53 0.79 Hydrated radius (nm) 43.0 2 Calcium 27.0 2 Magnesium 1.7 1 Potassium 1.0 1 Sodium Relative flocculating power Charges per molecule Cation Water molecule is polar: (+) on one end, (-) on the other end (+) (-) (+) Hydrated cation +
  13. 13. Effects of Cations on Soil Structure Negatively charged clay particle Negatively charged clay particle Dispersion/ Repel Clay particles behave independent of each other
  14. 14. Dispersed Soil Clay particles behave independent of each other. Poor Drainage
  15. 15. Effects of Cations on Soil Structure Negatively charged clay particle Negatively charged clay particle Flocculate Individual clay particles behave more as a larger aggregate +
  16. 16. Flocculated Soil Individual clay particles behave more as a larger aggregate
  17. 18. The cations are fully hydrated, which results in repulsive forces and expanding clay layers (hydration energy). The water molecules wedge into the interlayer after adding water Dry condition (Interlayer) Clay layers cation
  18. 19. Nutrient Movement to Root Diffusion Dominant for K & P Mass Flow Dominant for Ca & Mg and anions Root Interception <3%
  19. 20. Plant Root Uptake of K Two main groups of K transporters: High affinity group which are very selective for potassium and reach their maximum uptake rate at low soil solution K concentrations Low affinity group which are less selective and require much higher soil solution K concentrations to reach their highest uptake rate. High concentrations of Ca, Mg, and Na can interfere with uptake. The proton pump pushes H+ out through the plasmalemma creating an electrochemical gradient (more negative on the inside). 25 to 50% of the energy flow in a root hair cell is used to drive the proton pump
  20. 21. Clay Effect on K Uptake
  21. 22. Optimum Percent Saturation Ranges 1.5-3 1.5-3 2-4 2-4 3-4 3-5 4-6 K% <5 <5 <5 <5 <5 <5 <5 Na% 5-20 60-80 30+ 5-20 60-80 26-30 8-20 60-80 21-25 8-20 60-80 16-20 8-20 60-80 11-15 8-20 60-80 6-10 10-20 60-80 0-5 Mg% Ca% Soil CEC
  22. 23. K Fertilizer Recommendations Example: Soil Test K = 45 ppm CEC = 5 Target K ppm (Table) = 116 ppm (subtract) Soil Test K = 45 ppm To be Applied 71 ppm Convert to K 2 O lbs/acre (x2.4) = 170 488 2.5 50 439 2.5 45 390 2.5 40 341 2.5 35 293 2.5 30 244 2.5 25 197 3 20 215 4 15 188 5 10 116 6 5 27 7 1 Target K ppm BCSR % CEC
  23. 24. Mg Fertilizer Recommendations Example: Soil Test Mg = 65 ppm CEC = 5 Target Mg ppm (Table) = 90 ppm (subtract) Soil Test Mg = 65 ppm To be Applied 25 ppm Convert to Mg lbs/acre (x2.0) = 50 600 10 50 540 10 45 480 10 40 420 10 35 360 10 30 300 10 25 240 10 20 210 12 15 160 13 10 90 15 5 18 15 1 Target Mg ppm BCSR % CEC
  24. 25. Fertilizer Soil Acidification <ul><li>Alkaline Fertilizers </li></ul><ul><ul><li>Potassium Nitrate </li></ul></ul><ul><ul><li>Calcium Nitrate </li></ul></ul><ul><li>Slightly Acidifying – 2 lbs Lime per lb N </li></ul><ul><ul><li>Urea </li></ul></ul><ul><ul><li>Ammonium Nitrate </li></ul></ul><ul><ul><li>UAN Solutions (28%) </li></ul></ul><ul><li>Moderately Acidifying – 3 lbs Lime per lb N </li></ul><ul><ul><li>Diammonium Phosphate </li></ul></ul><ul><li>Severly Acidifying – 5 lbs Lime per lb N </li></ul><ul><ul><li>Ammonium Sulfate </li></ul></ul><ul><ul><li>Mono Ammoniumm Phospahte </li></ul></ul>
  25. 26. Elemental Sulfur lb/Acre Acidification 2600 1500 7.0 8.5 1400 800 7.0 8.0 700 400 7.0 7.5 CEC 8-15 CEC <7 Target pH Starting pH
  26. 27. Gypsum (CaSO 4 ) pH Correction Gypsum (tons/acre foot) = 1.7 x CEC x (Na% - 5%) CaCO 3 + H + (acid) = HCO 3 + Ca +
  27. 28. Comments or Questions?

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