Use and management in the quantity/intensity ratio and adsorption of potassium in Vertisol

Abstract

The availability of K for plants depends on the amount of exchangeable potassium (Q) and potassium in solution (I), and the Q/I ratio. The objective of this study was to evaluate the availability of K for crops using the Q / I curves and to adjust the Langmuir and Freundlich isotherms to K adsorption data in Vertisol. Samples of Vertissolo were collected with natural tree vegetation (“forest”) and annual crops (“crop”) in two locations. K adsorption data on the samples were used to construct adsorption isotherms, obtaining the coefficients of the Freundlich and Langmuir equations. The Q/I curve was obtained by plotting QAK (I) versus ΔK (Q), and indicated the presence of low labile K values. The Vertissolo samples from the Galante district showed higher availability of K in the solution of these soils. The adsorption isotherms demonstrated that the adsorbed K amounts increased with the concentration of the equilibrium solution. The Langmuir and Freundlich models are well adjusted to soil samples. The soil sample collected in Galante in the "forest" use and management system had a higher maximum adsorption capacity of K. In Queimadas, the retention of potassium in the "crop" was higher than in the "forest".