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Unformatted text preview: 1 Soil Acidity Summary Acidity is a master variable Acidity affects the availability of nutrients Acidity affects microbial activity Acidity dictates and reflects vegetation type Acidity impacts the mobility of pollutants (solubility, adsorption) 1. Low pH = acidic conditions, high H + concentration 2. Bases are the opposite of acids. Acids and bases neutralize each other. 3. Acids come from CO 2 , acid functional groups on O.M. roots, acid rain, Al 3+ 4. The two cations considered acidic in soils are H + and Al 3+ . 5. Al 3+ splits water and take hydroxides, leaving H + in soil solution => acid. 6. There are 2 types of soil acidity: active and exchangeable. 7. Active acidity is the hydrogen ions in soil solution (measure with a pH meter) 8. Exchangeable acidity is associated with Al and H on exchange sites. 9. Measurement of total soil acidity requires displacement of exchangeable acidity 10. Exchangeable acidity can be many times greater than active acidity in soils 11.Base saturation refers to the percentage of the total CEC occupied by base cations 12. High base saturation indicates greater numbers of beneficial cations on exch. Sites. 13. Acid soils tend to have low base saturation. 14.CEC alone is not necessarily a good indicator of fertility. Summary 15. Florida soils tend to be acidic because of high rainfall that is somewhat acidic. Acid cations from rainfall displace base cations. 16. Soils are able to resist changes in pH – soil buffering. 17. Soils resist changes in pH because of cation exchange. 18. If acid is added to soil, some of the H + will leave the active acidity pool to occupy exchange sites 19. If a base like NaOH is added to soil, OH- will neutralize acid, but Na + will displace acid from exchange sites. pH will not decrease as much as expected 20. We typically increase the pH of soil using compounds like CaCO20....
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This note was uploaded on 07/31/2011 for the course SOS 3022 taught by Professor Staff during the Fall '08 term at University of Florida.
- Fall '08