Abstract: The K supplying capability and characteristics of five conventional organic fertilizers，e．g．，cattle manure，pig manure，chicken manure，crop residue and green manure，are studied．The results show that the fertilizer K which is converted into rapidly available K of soil reaches a balance about 30 days of culturing in soil，but the fertilizer K which is converted to slowly available K of soil tends to steadiness after 70 days．The transformation rates of the available K of fertilizers in soil are about 50％～87％，and those of the slowly available K are about 50％～ 80％．In different K sources ，the K supplying capability of wheat straw is higher than that of K fertilizer，but that of three manures is lower than that of fertilizer K ．The K supplying capability of organic fertilizer is related to soil types and soil environments．