Adsorption and Availability of Phosphorous Following the Application of Limestone to an Acid, Aluminous Soil1
- J.T. Sims and
- B. G. Ellis2
Changes in the adsorption and availability of P in an acid, aluminous soil (surface and subsoil) were evaluated following liming to neutralize 1N KCl-exchangeable Al (minimal liming) or to pH 6.8 as determined by the SMP (Shoemaker-McLean-Pratt) buffer method. Langmuir adsorption isotherms were utilized to ascertain changes in P adsorption. A greenhouse bioassay was conducted to evaluate differences in P availability to plants (Oats, Avena sativa L. cv. Korwood) due to liming and incubation treatments. Results from these studies confirm that minimal liming is the most effective approach, from both agronomic and economic standpoints. Minimal liming optimized P uptake and minimized the P adsorption maxima (Langmuir b values). Liming by the SMP recommendation did not improve P uptake despite the application of three times as much lime, and also markedly reduced exchangeable Mg. Aging of adsorbate surfaces in the soil reduced their bonding intensity for P (Langmuir K), as did increasing soil pH. Development of ordered, less soluble Al-OH polymers with fewer nonstructural OH groups capable of ligand exchange with P is postulated as the mechanism underlying these observations. Increases in pH-dependent negative surface charge and P adsorption by free CaCO3 may be involved.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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