Potassium Fixation and Release in Rubber Plantation Soils in Southern Thailand

Potassium (K) is an essential element for rubber tree growth and latex synthesis. K fixation and K release are the key factors that control K availability in soil. This objective of this research was to investigate the potential of K fixation and K release in coarse, medium, and fine textured soil groups on a rubber plantation in southern Thailand. The results indicated that the soil used for this study had both available K and fixed K in low level. The potentiality of K fixation was high when low K concentrations (10-50 mg K kg-1) were added to the soil. The percentage of K fixation in fine textured soil groups was higher than in medium and in coarse textured soil groups, respectively. The buffering coefficient for K (BCK), which indicates the ability of K fixation in soil, found that the capacity of K fixation and K release in fine textured soil groups was higher than in medium and in coarse textural soil groups, respectively. The amount of K release was higher in soil with a higher dosage of K fertilizer application. Therefore, the management approach for available K in rubber growing soils should be applying a combination of K fertilizer and organic fertilizer to enhance K level and the ability of K adsorption in soil, especially for coarse textured soil groups with a lower K buffering capacity than fine textured soil groups.