Abstract:In order to reveal the effect of long-term organic fertilization on soil fertility of irrigated desert soil, based on the long-term fertilization experiment of irrigated desert soil in Hexi oasis irrigation area of Gansu province (1988 to present), four treatments including organic phosphate fertilizer (MP), organic and inorganic NPK (1/2 MN + P), nitrogen and phosphorus (NP) and no fertilizer (CK) were designed. Based on the existing test data of soil nutrient and crop yield and those data measured in the 31st year, the effects of long-term organic fertilization on soil fertility and crop yield in desert soil were studied. The results showed that compared with the initial value of the experiment, the average soil nutrient value of the past years and that in the 31st year of organic-inorganic combined application all increased, which indicted that the soil organic matter increased by 72.5% and 24.9%, soil total nitrogen increased by 72.3% and 25.7%, and soil total potassium increased by 16.1% and 33.0%. Compared with non-fertilizer control (CK), soil organic matter increased by 54.9% and 19.1%, soil total nitrogen increased by 47.3% and 14.9%, and soil total phosphorus increased by 73.0% and 15.3%. Combined application of organic and inorganic fertilizer could effectively reduce soil pH. Compared with CK, the average value of the past years and that in the 31st year of organic-inorganic combined application showed that the yield of wheat/maize intercropping system increased by 149.2% and 139.2%, fertilizer contribution rate (FCR) was 0.58, coefficient of variation (CV) was 0.21, and sustainability index (SYI) was 0.61. Nutrient and yield indexes all reached high quality level. In Hexi oasis irrigation area, Gansu province, long-term combined application of organic and inorganic could continuously and significantly increase the contents of soil organic matter, total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus and available potassium, reduce soil pH and increase soil fertility and the contribution rate of fertilizer. It could significantly improve the yield, stability and sustainability of wheat/maize intercropping system. This study could provide decision-making basis for scientific fertilization of farmland soil and sustainable development of agriculture in Hexi Oasis Irrigation Area of Gansu Province.