“…This could be due to the highest sand content in the soil. Because of their lower CEC or clay content compared to soil 3, therefore most of the K supplied by mineral fertilizer or released from organic amendments in calcareous or sandy soils (soil 1, 4) is subjected to leaching (Hamed & Amin, 2017). In regard to soil 1, 2, 3 and 4, values of PBC K were 11.9, 13.6, 18.7, 13.90, 26.2 cmol kg −1 /(mol L −1 ) 0.5 , 26.2, 29.9, 29.4, 26.9 cmol kg −1 /(mol L −1 ) 0.5 , 21.4, 25.5, 26.5, 27.3cmol kg −1 /(mol L −1 ) 0.5 and 14.8, 15.1, 20.1, 14.4 cmol kg −1 /(mol L −1 ) 0.5 for 0, 50, 100, 150%K, respectively.…”