ChileanJAR

Potassium deficiency in grapes cv. Sauvignonnase and Semillon wasfoundto beclosely associated with subsoil exchangeable K levels below 50 ppm (AcNH₄ at pH 7.0 extraction). Depending upon soildepth and amount of K added to a soil sample, the degree of Kfixation varied between 6 and 47%. No f ixation was found however in the A horizon, even though it presented the same type of clay (vermiculite). It was assumed that, at the present level of available K in this horizon, the sites of absorption are already saturated, therefore when K is added it will increase the available K. The authors suggest that this property is very important to predict both the dosage and/or localization of the fertilizer.