Effects of a long-term located fertilization on the fertility and productivity of Shajiang Black Soil

A systematic study concerning the effects of a long term application of chemical fertilizers，organic manure separately or both of them on the soil nutrient content，basic productivity and crop yield in Shijang Black Soil was conducted．The results show that the long-term fertilization can increase the contents of,soil organic matter，available N and P．But there is a greater difference among the fertilizer combinations，the effect of the treatment applying organic manure combined with chemical fertilizers is most remarkable in several treatments，but the application of potassium must be attached importance at the same time．Only the treatment applying single organic manure can increase thc (fil available K content，the descending rate of the treatment applying chemical N and P is the fastest in all treatments．and it decreases by 25．8％during 15 years．The change of available N without fertilizers(CK)treatment is greater than that of other nutrients，being 26．5％ fewer than that of 15 years before．but other nutrients change little．The crop yield with the treatment applying organic manure combined with chemical fertilizers is lower than that with the treatment applying single chemical fertilizer in prophase，but it is higher in other phases．With the time prolonging，the basic productivity of Shajiang Black Soil is declining，and the soil supplies more nutrient for maize or soybean than wheat．