Abstract

BOLIO-LOPEZ, Gloria Ivette et al. Potassium Dynamics in Vertisols and Fluvisols Planted with Sugarcane. Terra Latinoam [online]. 2008, vol.26, n.3, pp.253-263. ISSN 2395-8030.

The size of potassium (K) reservoirs and the effect of K supply on the dynamics of soluble K (Ks) fractions, exchangeable K (Ke), non-exchangeable K (Kne), and buffer capacity of K (cK) of a Vertisol and a Fluvisol planted with sugar cane in three plantations with 10, 20, and 30 years of monocropping were determined. At each site a compound soil sample (100 kg for each soil type and age of plantation) was collected. Of this soil mass, 250 g subsamples were weighed, 100 mg kg^-1 K were added as KCl. These subsamples were mixed uniformly, moistened to field capacity, and incubated during 0, 1, 3, 7, 15, 30, 60, 90, 120, and 150 days. The test consisted of five replications; for each incubation date the corresponding samples was withdrawn, and Ks, Ke, and Kne were determined. The size of the native reservoirs (time 0) of Ks, Ke, and Kne varied according to soil type, regardless of years of monocropping. Ks and Ke concentrations were higher in Fluvisol than in Vertisol, caused by the presence of illite-type lime particles, rich in K. As a consequence of the addition of soluble K, the concentration of Ks and Ke increased in both soil types, regardless of years of monocropping, following the same tendency as observed in determining the size of native reservoirs. The decrease in the soluble and exchangeable forms of K and the increase of the non-exchangeable K ended at 30 days of incubation. Vertisol presented a cK equal to that of Fluvisol (36%). There was no effect of monocropping time on the K dynamics.

Keywords : potassium buffer capacity.