| The 21-year long-term fertilization experiment was carried out on irrigated desert soil in the oasis area of Zhangye.The results showed that,as the yield of no-fertilizer treatment decreased gradually,the yield-increase effect of fertilization was increased year after year,and the increase rate of balance fertilization was remarkably higher than N fertilizer.The soil productivity of N fertilizer treatment was reduced from 89.8% in the 1st rotation period to 28.5% in the 7th period.Under the condition of no organic manure,the K fertilizer became effective to the crops from the 3rd rotation period,and the yield increase rate was 5.5%~22.7%.Under the condition of long-term compounding application of N,P and K fertilizers,the crop yield kept steady,and the average soil productivity was 93.5%,showing that the compounding application of fertilizers didn't destroy the soil productivity.The interaction effect of organic manure and N fertilizer was positive,whereas that of organic manure and P or K fertilizer was negative.Without any fertilizer,the average decrease rate of soil productivity was 59.6% during the 1st to the 4th rotation period,and the decrease rate kept 16.7%~22.7% during the 5th to the 7th period.The contribution quotient of chemical fertilizer,organic manure and soil natural fertility to crop yield was 50.5%,21.6% and 19.0% respectively. |