EFFECT OF POTASSIUM FERTILIZERS ON QUANTITY-INTENSITY PARAMETERS IN SOME ARGENTINE SOILS

The parameters obtained from the quantity-intensity (Q/I) isotherms ha ve been used by several authors as criteria to estimate the immediate availability of labile potassium (K) in a soil. The aim of this work w as to study how these parameters have been modified in four agricultur al soils in Argentina by the addition of K (0 to 936 kg K2O ha(-1)) in an incubation trial simulating K fertilizers application. In two of t he soils, the increase in the labile forms of K was proportional to th e amount of added K and the recovery percentages were high. In the oth er soils, a contrasting behavior was found. This difference might be d ue to different fixing capacity of the soils, which was related to the clay content and mineralogical composition of this fraction. The slop es of the Q/I curves for each soil indicate that the potential buffer capacity (PBC) was similar for the different treatments over the range of K added. The addition of K produced proportional increases in ARe and Delta Ko values. This could be attributed to the presence of non s aturated planar sites at the highest rates of K applied.