Abstract
Twenty four soil series, representing the parent materials: less and moderately weathered alluvium; limestone; shale and sandstone; diorile, granite, and granodorite; and less and moderately weathered loess were investigated for K fixation in relation to clay mineral composition and characteristics. Potassium fixation was determined by equilibrating the soil with 1 g K per kg soil for one month with alternate wetting and
drying cycles. The moderately weathered alluvial soils and the diorite, norite, granite, and granodiorite derived soils had the highest K fixation. The less weathered alluvium and limestone derived soils had the lowest K fixation. Also, the less weathered alluvial soils had lesser K fixation than the moderately weathered alluvial soils. Potassium fixation varied from 400 to H70 mg kg' in moderately weathered alluvial soils and from
240 to 870 nig kg'I in diorite and norite derived soils. The soils derived from limestone mostly released K or fixed a little K. However, the limestone derived soils which had mixture of shale fixed HO to 400 mg K per kg soil. Potassium fixation in loess soils varied from 200 to 750 mg kg'1. In the sandstone derived soils (Balkassar) K fixation ranged from 500 to 600 mg kg'1. Potassium fixation had no correlation with total clay content as usually thought. Potassium fixed and K extractahle with IN NH4OAc were negatively correlated. The results have been explained in relation to mineralogical composition of these soils.
Z.I. Awan, M. Arshad , M,S. Akhtar. (1998) POTASSIUM FIXATION IN RELATION TO SOIL PARENT MATERIAL AND WEATHERING STAGE IN PAKISTAN, The Journal Soil & Environment , Volume 15, Issue (3-4).
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