紫花苜蓿根际效应对河套灌区土壤盐分和养分的影响

[目的]从时间和空间尺度上分析紫花苜蓿(Medicago sativa L.)不同生长期内根际土壤盐分和养分的动态变化规律,揭示紫花苜蓿生长过程中根际效应对内蒙古河套灌区盐碱地土壤盐分和养分的影响作用,为北方大型灌区盐碱化农地土壤的植物改良措施提供科学依据.[方法]以内蒙古河套灌区盐碱化土壤为研究对象,以当地土著耐盐牧草紫花苜蓿为试验植物,通过盆栽根袋模拟装置,采集分析不同生长期内(20、40和60 d)紫花苜蓿根际和非根际土壤的pH、盐分和养分含量,并分析其变化规律.[结果]随着紫花苜蓿的生长,其根际土壤的电导率、pH、Na+、K+、Mg2+、Cl-和CO32-含量逐渐降低;根际和非根际土壤中Na+/K+和Cl-/SO42-均呈逐渐降低趋势,根际土壤中Cl-/SO42-相对于非根际土壤降低程度较明显.非根际土壤中总氮、总磷和有机质含量总体上呈下降趋势,根际土壤中总氮含量相对稳定,总磷含量降低,速效磷含量显著升高(P<0.05).[结论]紫花苜蓿根际效应可降低河套灌区盐碱化土壤的pH、电导率和主要盐分离子浓度,提高磷的有效性,有助于盐碱地土壤理化性质的改善及有效肥力的增强,且其影响作用随紫花苜蓿生长时间的延长逐渐加强.

Rhizosphere effects of alfalfa on soil salt and nutrient in Hetao irrigation area

[Objective]In 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.[Method]In 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.[Result]With 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).[Conclusion]The 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.