Abstract:The changes of soil physical and chemical properties under wheat-alfalfa rotation in the desert area of Northern Xinjiang Plain were studied to reveal the dynamic pattern of soil salinity and nutrients in the process of grain-alfalfa rotation,therefore providing scientific basis for the adjustment of planting structure and sustainable utilization of farmland ecosystem.The soil total salt content,pH value,organic matter,nitrogen,phosphorus and potassium were followed up for 5 years in wheat-alfalfa rotation system.The rotation of alfalfa in wheat effectively decreased soil salt content and pH value,with soil salt content reduced from 0.79 g/kg to 0.63 g/kg in the fourth year of rotation,and an average decrease in soil pH by 6.64%,an average increase in soil organic matter by 19.07%.Soil total nitrogen content increased from 0.52 g/kg before rotation to 0.65 g/kg,and the hydrolysis nitrogen content was significantly lower than that before rotation.Soil phosphorus content fluctuated up and down,and the total phosphorus decreased from 0.98 g/kg to 0.93 g/kg and the available phosphorus decreased from 6.18 g/kg to 2.97 g/kg in the four-year rotation.Soil available potassium content initially decreased and followed by an increase.After rotation,the minimum value of soil available potassium content was 260.44 mg/kg,which was in a potassium-rich state.Consequently,the introduction of alfalfa into the grain farming system in the desert area of northern Xinjiang plain can effectively improve the soil organic matter content,increase the total nitrogen storage and reduce the salinity.However,in the fourth year of alfalfa growth,nitrogen and phosphorus fertilizer should be appropriately supplemented,but with no need for the addition of potassium fertilizer.