POTASSIUM STATUS IN THE SOILS OF BAHTIM PERMANENT EXPERIMENT UNDER DIFFERENT CROP ROTATIONS AND FERTILIZER TREATMENTS

Composite surface soil samples were taken from plots (Bahtim permanent experiment) receiving mineral and farmyard (FYM) fertilizer treatments in case of the one-, two- and three-year rotations. These soil samples represent the impact of subjecting such soils for about 100 years to prolonged cropping and fertilization treatments. Soluble, exchangeable, plant-available potassium in conjunction with the potassium intensity of these soils were determined. Moreover, the K-fixation capacity was considered in this study. The obtained data show an obvious decrease in potassium forms in case of the two- and three-year rotation compared with their levels in the one-year rotation. This depends on the crops grown in every rotation. The decrease in K- availability in soils have its impact on crop response to K- applications. This trend should be considered in managing the fertilization programs in the old lands.