Abstract: ObjectiveIn perspectives of time and space,the dynamic variation of soil salt and nutrient in rhizosphere soil of alfalfa(Medicago sativa L.)during different growth periods.The rhizosphere effects of alfalfa on salt and nutrient in saline-alkali soil of Hetao irrigation area,Inner Mongolia was studied.With these efforts,this paper aimed to provide scientific basis for plant improvement in saline-alkali soil in large irrigation area of northern China.MethodIn this study,saline-alkali soil from Hetao irrigation area in Inner Mongolia was used as the research target,and alfalfa,an indi-genous salt-tolerant forage,was selected as the experimental plant.Through lab potted plant device,pH,salt content and nutrient content in rhizosphere soil and non-rhizosphere soil of alfalfa during different growth stages(20,40 and 60 d) were sampled and analyzed,and their variation regulations were studied.ResultWith the growth of alfalfa,electric con-ductivity(EC),pH,Na+,K+,Mg2+,Cl-and CO32-contents decreased gradually in the rhizosphere soil.Na+/K+and Cl-/SO42-ratios showed a decrease trend in both rhizosphere soil and non-rhizosphere soil,and Cl-/SO42- in rhizosphere soil de-creased more greatly than that in non-rhizosphere soil.In non-rhizosphere soil,contents of total nitrogen,total phosphorus, and organic matter generally decreased.While in rhizosphere soil,total nitrogen content was relatively stable,total phos-phorus content decreased,and content of available phosphorus increased significantly(P<0.05).ConclusionThe rhizo-sphere effects of alfalfa decrease pH,EC,and salt ion concentrations in saline-alkali soil in Hetao irrigation area,improve soil physical and chemical properties and effective fertility.In addition,these effects gradually strengthens as alfalfa grows.