EXTRACTION METHODS AND POTASSIUM AVAILABILITY FOR SOYBEAN IN THE PARANA STATE’S SOILS, BRAZIL

Abstract

Evaluating the potassium (K) availability to the plants can be performed by different methods. In general, multielement methods are employed and they are used for K due to increase operational of soil testing laboratory. The efficacy of ammonium acetate, Mehlich-1, Mehlich-3 and ion exchange resin soil K extractantsin determining the K availability for soybean [Glycine max L. (Merrill)], in different Parana’s soils, were investigated in this study. Twelve soil samples, collected from the upper layer 0–0.20 m, were cultivated with soybean for 42 days in greenhouse conditions. The average amount of available soil K extracted in test soils was found, displayed in decreasing order: ammonium acetate Mehlich-3 Mehlich-1 = ion exchange resin. The correlation coefficients between the K extracted content by ammonium acetate, Mehlich-1, Mehlich-3 and ion exchange resin and the K accumulated amount in the plants were, respectively, 0.90, 0.77, 0.88 and 0.89. The efficacy of ammonium acetate, Mehlich-3 and ion exchange resin extractants in assessing plant-available K in soils from Parana State were similar. The Mehlich-1 was the least efficient in estimating plant-available K in Parana’s soils.