Title:	Cation selectivity coefficients and diffusion parameters of potassium in soils of the state of Rio Grande do Sul, Brazil.
Authors:	CIPRANDI, M. A. O. WIETHOLTER, S.
Affiliation:	M. A. O. CIPRANDI; SIRIO WIETHOLTER, CNPT.
Date Issued:	1994
Citation:	Revista Brasileira de Ciência do Solo, Campinas, v. 18, n. 3, p. 395-405, set./dez. 1994.
Description:	Transport of potassium (K) in the soil towards roots depends mainly on diffusion. There is a lack of routine procedures for the determination of diffusion parameters. The objectives of this study were to: 1) determine multielement selectivity coefficients of soil exchange reactions of the main soil cations; 2) estimate these coefficients through soil factors routinely determined; and 3) calculate diffusion parameters of K using selectivity coefficients, activity in the soil solution, and concentration of the exchangeable phase. Soil solution cation concentrations were determined by strontium equilibration, and exchangeable cations were determined by extraction with IM NH,CI. Average values of the selectivity coefficients, using Gapon's equation, were: kç, = 0.84, ky, = 1.15, ky, = 0.78, kNS = 0.71, kMN = 1.14, kN? = 0.48, kDr = 0.34, kMx = 0.14 and k3! = 3.07, in which (M», represents the mono- Ca valent cation activity equivalence of K and (D*),, represents the divalent cation activity equivalence of Ca, The soil factors best related to these selectivity coefficients were pH in water, pH in CaCl,, pH in the SMP buffer solution, clay content, organic matter content, and the activity ratio between divalent cations and K. Regression equations between these soil parameters and the selectivity coefficients presented rº? values greater than 0.8. Buffer power of the soil for K was calculated with a differential equation including selectivity coefficients, activity in the soil solution, and concentration on the exchange phase of Na, K, Sr, Ca, Mg, Mn, and Al. The utilized methodology allowed an easy determination of soil K diffusion factors.
Thesagro:	Oxisol Solo
Type of Material:	Artigo de periódico
Access:	openAccess
Appears in Collections:	Artigo em periódico indexado (CNPT)