Resumo

BUGARIN MONTOYA, Rubén; GALVIS SPINOLA, Arturo; HERNANDEZ MENDOZA, Teresa Marcela  e  GARCIA-PAREDES, Diego. Potassium buffering capacity and release kinetics in soils. Agric. Téc. Méx [online]. 2007, vol.33, n.1, pp.73-81. ISSN 0568-2517.

Buffering capacity and potassium (K) release kinetics in soil "determine" its availability for crops. Both characteristics were evaluated in three soils with different cationic exchange capacity (CEC), with the objective of determining the effect of added Potassium and incubation period on potassium content in the soil solution and exchangeable Potassium, its buffering capacity and release the kinetics of Potassium. The study was carried out in the Soil Fertility Laboratory at the Colegio de Postgraduados, Montecillo, Estado de Mexico, Mexico from January 2000 to February 2002. Four levels of Potassium were added: 0, 100, 200 and 400 mg kg^-1 of soil with KH₂SO₄ and four incubation periods 0, 6, 12 and 24 h at field capacity and at temperature of 3 5 °C. Data was analyzed as factorial completely random design with three replications. After treatments, soil samples were submitted to successive Potassium extractions with CaCl₂ 0.01M and to the standard procedure of K extraction with NH₄OAc 1N, pH 7.0 and HNO₃1M. The addition of KH₂SO₄ showed significant increases of Potassium in the soil solution and exchangeable K, whose magnitudes were associated to CEC (PrF= 0.0001). The Potassium content in the soil solution and exchangeable Potassium were linearly correlated and the slope corre sponded to the buffering capacity with values of 0.92, 0.67 and 0.50 for the soils with CEC of 3.05, 11.25 and 30.15 cM kg^-1 of soil, respectively. The incubation period did not influence buffering capacity, content of Potassium in the soil solution and exchangeable Potassium values. Potassium desorption kinetics was adjusted to a potential function, meanwhile the accumulation of desorpted Potassium to a logarithmic function, the corresponding slopes were correlated to CEC, with r = 0.80 ** and 0.98**, respectively.

Palavras-chave : Desorption; exchangeable potassium; potassium in soil solution.

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