Four factorial field trials for some main field crops. i.e. wheat, faba bean, cotton and rice were carried out at Sakha Agric. Res. Station to evaluate • potassium fertilization from two fertilizer sources, i.e. K2SO4 and KCI. The important results could be summarized in the following points: • Potassium fertilization with 24 kg K20/fed. (as K2Sa4 fertilizer) in‌creased crop's yields by 20.76. 24.45, 6.80 and 8.10 % for wheat, faba bean, cotton and rice, respectively; except for faba bean, k-fertilization with 12 kg K20/fed. (as KCI fertilizer) insignificantly in‌creased such crops with parallel increments of 4.7, 16.49, 1.1 and 2.6%, respectively. • High K-rates of 48 kg K20/led. (as K-sulfate) or 24 kg K20/fed. ( as K-chloride) were not proper rates for such crops because of the insig‌nificant increments for the first fertilizer and side effects of chloride anion Cr for the second fertilizer. • Interaction effects between K2934 and KCI fertilizers on crops' yields have revealed some antagonistic effects related to S02" and Cr an‌ions from soil and/or fertilizer especially in case of adding high K-rates which affected most nutrient's absorption by plants and subse‌quent crop's yields. • For the studied soils, it may be recommended that potassium sulfate fertilizer is more effective than potassium chloride fertilizer for the crops under research.