Effects Of Continuous Cropping And Rotation On Rhizosphere Microorganism Diversity And Quality Of Astragalus

Continuous cropping obstacles often lead to the decline of quality and yield of traditional Chinese medicines.Crop rotation can effectively alleviate continuous cropping obstacles.Currently,there are few studies on rotation of traditional Chinese medicines.Astragalus membranaceus(Fisch.)Bge.var.mongholicus(Bge)Hsiao(A.mongolicus),as a genuine medicinal material in Inner Mongolia,Shanxi and Gansu province,is often used in clinical medicine.This experiment took A.mongolicus as the research object,and compared its biomass,root rot disease,medicinal quality,soil nutrient and enzyme activity after five years crop rotation with Brassica napus,Solanum tuberosum,Avena sativa,Scutellaria baicalensis and A.mongolicus by pot and field experiments.The 16 S r RNA sequencing technology was used to compare the bacterial community composition and diversity in rhizosphere,endosphere and bulk soil of A.mongolicus after crop rotation with different crops.The effects of continuous cropping and crop rotation on the quality of A.mongolicus and soil health from various perspectives was analyzed in this experiment,and explored the bestcrop rotation mode to improve the obstacles of continuous cropping of A.mongolicus,which plays an important role in the sustainable production of A.mongolicus.The results are as follows:1.After five years of continuous cropping of A.mongolicus,the plant growth was slow,the biomass was low,and the quality of medicinal products decreased.Crop rotation promoted the growth of A.mongolicus.After crop rotation with Avena sativa,the biomass indexes were significantly increased,and the contents of flavonoids and Astragaloside IV in the root of A.mongolicus were significantly increased.That is to say,crop rotation of A.mongolicus and Avena sativa was beneficial to plant growth and improved medicinal quality.2.After five years of continuous cropping of A.mongolicus,soil nutrient content and soil enzyme activity decreased significantly,while after crop rotation of A.mongolicus and Avena sativa,soil organic matter,total nitrogen,total phosphorus and total potassium contents were increased,and soil nutrients were sufficient.At the same time,the soil catalase,soil urease,soil alkaline phosphatase and soil saccharase activities increased after crop rotation,which indicated that the rotation of A.mongolicus and Avena sativa could effectively reduce the soil obstacles caused by continuous cropping and had a positive effect on the growth of A.mongolicus.3.Continuous cropping and crop rotation mainly affected the microbial structure of rhizosphere soil,but had little effect on bulk soil and endosphere bacteria.Alpha diversity index of rhizosphere bacterial community was optimized after crop rotation,and more specific OTUs were retained,which indicated that crop rotationcould improve the diversity and richness of rhizosphere bacteria.4.The composition and abundance of dominant bacterial communities in the rhizosphere of A.mongolicus were affected by continuous cropping and crop rotation,sampling time and soil nutrients.Continuous cropping reduced the abundance of beneficial bacteria and decreased the diversity of bacteria,which led to the serious root rot of A.mongolicus.Crop rotation increased the relative abundance of beneficial bacteria such as Anaerolineae,Rhizobiales and Burkholderiale,which played a positive role in the growth and disease reduction of A.mongolicus.That is to say,the crop rotation of A.mongolicus and Avena sativa is beneficial to soil health and growth of A.mongolicus,which is a reasonable rotation measure to alleviate the obstacles of continuous cropping of A.mongolicus.