Study On Interaction Between Nutrient Uptake And Rhizosphere Soil Microbial Community Structure Of Bitter Gourd Under Continuous Cropping

Continuous cropping obstacles are the bottleneck that restricts the healthy development of bitter gourd industry.The autotoxicity of plant root exudates,the change of soil microbial community structure,and soil nutrient imbalance are the main factors leading to continuous cropping obstacles.Rhizosphere soil microorganisms are a key factor in maintaining nutrient cycling in the soil ecosystem.Their diversity and richness affect plant nutrient absorption,soil physical and chemical properties,and enzyme activities.In this study,continuous cropping bitter gourd plants and rhizosphere soil were used as research objects,and chemical methods were used to analyze the nutrient absorption laws of balsam gourd plants,soil physical and chemical properties and enzyme activities,a combination of high-throughput sequencing technology and bioinformatics methods were used to analyze the dynamic changes of rhizosphere soil microbial community structure.These researches will comprehensively evaluate the interaction effects of bitter gourd nutrient absorption and rhizosphere soil microbial community structure.The main results were as follows:1.The total dry matter allocation ratio of the first crop of bitter gourd is root: vine: leaf: fruit=1:31.24: 27.80: 31.49,total nutrient accumulation of bitter gourd: K> N> P> Ca> Mg> B> Zn,the absorption ratio of each element is N: P: K=1: 0.15: 1.33,Ca: Mg=1: 0.19,Zn: B=1 : 1.6;The total dry matter allocation ratio of the second crop of bitter gourd is root: vine: leaf: fruit=1: 13.75: 12.43: 22.83,total nutrient accumulation of bitter gourd: K> N> P> Ca> Mg> Zn> B,the absorption ratio of each element is N: P: K=1: 0.26: 1.80,Ca: Mg=1: 0.26,Zn: B=1: 1.4.The dry matter accumulation of bitter gourd has a significant positive correlation with the accumulation of nutrients.2.There are significant differences in soil physical and chemical properties and enzyme activities in different continuous cropping stubbles of bitter gourd.The content of soil organic matter,soil macronutrients(alkali-hydrolyzable nitrogen,available phosphorus,available potassium),soil major element and soil catalase activities of the second crop 80 d and 120 d after sowing were significantly higher than those of the first crop.The content of soil medium element(exchangeable calcium and exchangeable magnesium)and acid phosphatase activity at 80 d after sowing were significantly higher than those of the first crop;the content of soil trace elements(available boron)at 120 d after sowing was significantly higher than that of the first crop.3.The soil microbial community structure in the rhizosphere of bitter gourd differed significantly in different continuous cropping stubbles in the same growth period.The relative abundance of Microvirga and Sphingomonas in the second crop decreased,and the relative abundance of Chloroflexi increased.The relative abundance of Rhizobium,Sphingobium,Roseiflexus,Humicola,Neocosmospora in the second crop increased.4.Under the condition of two consecutive crops,there was a significant positive correlation between N accumulation of Rhizobium,Neocosmospora and Humicola.Microvirga was negatively correlated with K accumulation in bitter gourd.Corallomycetella was positively correlated with K accumulation in bitter gourd.There was a significant positive correlation between the accumulation of B with Sphingomonas.5.The urease activity was enhanced by Rhizobium,Neocosmospora and Humicola,and the content of alkali-hydrolyzed nitrogen in soil was increased,which promoted the absorption of N by bitter gourd.Microvirga and Corallomycetella increased the content of soil available potassium,which promoted the absorption of K by bitter gourd.Sphingomonas resulted in reduced absorption of B in bitter gourd.