| Millet,one of the main crops in northern China,plays an important role in agricultural production.Yellow River Pumping Irrigation Area in the middle arid region of Ningxia is one of the main dominant areas for millet cultivation in Ningxia.The region is characterized by drought,lack of rain,lack of water resources and single planting structure,and long-term continuous cropping of millet easily lead to a series of problems,such as soil quality decline,soil microbial diversity decline,etc.In this study,low water consumption and drought-tolerant crops were selected to alleviate the continuous cropping obstacles and water shortage in production,so as to optirnize the crop structure and build a healthy rotation model for millet production in the Yellow River Pumping Irrigation Area in the middle aris region of Ningxia.In this study,three rotation models of millet-soybean(MRG),millet-grain amaranth(MRA)and millet-quinoa(MRQ)were set up in the middle and region of Ningxia from 2017 to 2018,and to studied the physicochemical properties,enzyme activities and microbial community structure of rhizosphere soil.The main results are as follows:1.Compared with continuous cropping,rotation could increase soil moisture content,total nitrogen,total potassium,total phosphorus and organic matter content,and reduce soil pH and total salt content.The contents of total nitrogen,total phosphorus and total potassium increased by 13.20%,80.36%and 253.05%respectively in MRQ rotation treatment.The contents of organic matter increased by 25.36%,and the contents of pH and total salt decreased by 2.01%and 65.91%in the MRA treatment.2.The activities of catalase,urease and alkaline phosphatase were increased by different rotation models.In addition,besides the decrease of invertase activity under MRG treatment,soil invertase activity under MRG and MRQ rotation models also increased.Compared with continuous cropping,the activities of catalase and alkaline phosphatase in soil were significantly increased by 8.72%and 11.54%in MRQ treatment and 20.16%in MRA treatment.3.Compared with continuous cropping,rotation improved soil bacterial richness index(Chaol index,ACE index),fungal diversity index(Simpson index,Shannon index)and fungal richness index(Chao 1 index,ACE index),except that bacterial diversity index(Simpson index,Shannon index)of MRQ treatment was lower than that of continuous cropping,and that of MRG and MRA treatment was higher than that of continuous cropping.4.The relative abundance of Actinobacteria,Proteobacteria,Chloroflexi,Acidobacteria and Gemmatimonaaetes was 92.1%among 22 detected bacteria in all soil samples.Among them,under rotation model,the relative abundance of Proteobacteria,Chloroflexi,Acidobacteria and Gemmatimonaaetes increased by 4.66%-18.61%,0.85%-27.53%,25.54%-86.60%,11.52%-37.83%,while the abundance oiActinobacteria decreased by 8.42%-30.98%.Ascomycota was the dominant group of fungi,and the relative abundance of Ascomycota was 91.7%in all soil fungal.Rotation model reduce the proportion of harmful microorganisms in soil.Compared with CK,MRG,MRA and MRQ decreased by 2.73%,2.72%and 2.27%respectively.5.Compared with continuous cropping,the economic benefits of rotation model increased and soil environment improved.The economic performance was MRA>MRG>MRQ>CK.Compared with CK,MRA,MRG and MRQ increased by 287.19%,58.49%and 50.41%.6.Through comprehensive evaluation of different rotation model,it was found that the comprehensive scores of three rotation models were higher than those of continuous cropping,among which the millet-grain model had the highest score.Therefore,this model is recommended as the preferred model for millet rotation on Yellow River Pumping Irrigation Area in Ningxia. |
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