Optimization Of Rhizobia-Leguminous Green Manure-Tea Intercropping System And Its Preliminary Application In Chemical Nitrogen Fertilizer Reduction

The excessive use of chemical fertilizers has continuously reduced the quality of cultivated land in China,which has seriously restricted the sustainable development of China’s agriculture.Planting green manure can improve soil pH,increase soil organic matter,and increase soil microbial diversity.Among them,legume green manure and Rhizobium can form a unique symbiotic nitrogen fixation system to provide nitrogen for crops,provide nutrients,reduce the weeds in the field,and improve the environment of cultivated land.It has important development significance in traditional agriculture in China.Rhizobium has host specificity,which limits the wide application of legume green manure to a certain extent.Intercropping and cropping can expand the application range of legume green manure,but need to consider Rhizobium-legume green manure-crop,the three crops interact with each other,which in turn gives them a greater advantage in legume green manure.Tea is a special economic crop in China,and its perennial characteristics are very convenient for intercropping with legume green manure.In this paper,the Rhizobium of leguminous green manure in different growing seasons was firstly isolated and collected.Study on the interaction between Rhizobium-legume green manure-tea tree with Rhizobium of Astragalus Sinicus L.,and soybean was developed in tea garden.The intercropping of tea trees has been studied to reduce the effects of chemical nitrogen fertilizer application,tea growth and soil microbial flora changes.The results obtained are as follows:(1)A total of 20 Rhizobium strains were screened from the root nodules and root soils of legumes in different seasons such as Medicago sativa Linn,Viciavillosa Rothvar and Astragalus Sinicus L.(Chinese milk vetch).After 16S rRNA sequencing,15 Rhizobium strains were separated from the Viciavillosa Rothvar and belonged to Rhizobium leguminosarum.2 strains were separated from the Astragalus Sinicus L.and belonged to Mesorhizobium huakuii,and 3 strains were separated from the Medicago sativa Linn and belonged to Sinorhizobium meliloti.(2)The Mh93-nodA translation was constructed with Mh93 as the research object.The expression strain was fused,and the root exudates of tea trees were extracted for induction,and a pot experiment was used to simulate the intercropping environment.The results showed that the root exudates of tea tree could promote the expression of Rhizobium Mh93 nodulation gene;the growth of tea varieties and legumes in potted plants was better than that of single cropping.The preliminary screening mechanism for the selection of the optimal green manure Rhizobium in the field was established,which provided a way for selecting the appropriate Rhizobium-legume green manure in the intercropping system.(3)According to the results of pot experiment and seasonal factors,the Rhizobium-soybean-tea intercropping system was selected for field experiment.No chemical nitrogen fertilizer was applied during the experiment,and soybeans were inoculated with Rhizobium.Soil samples from different periods were collected for determination of total nitrogen,organic matter and soil pH value,and soil microbiology.After the flowering period,the total nitrogen in the soil was about 0.4476 g/kg,and the soil organic matter was about 37.5 g/kg,which was basically the same as the initial content of total nitrogen and organic matter in the soil before planting(0.4925 g/kg,37.9 g/kg).After the tea garden turned over the green manure,the soil pH value increased by 0.1,which provided a good environment for the improvement of tea quality.The soil microbial community diversity in different periods was analyzed.The data showed that the soil microbial community was different from that of the single cropping tea tree,and the microbial community diversity was improved.Cyanobacteria,Nitrospirae,Bacillus and other related microorganisms involved in nitrogen cycle and organic matter decomposition have increased,the proportion of Acidobacteria associated with soil pH value is reduced,Conducive to soil nitrogen,organic matter and soil pH value.The quality of the tea after turning green manure was better than that of the monoculture tea.Based on the above results,the effects of non-legume root exudates on the nod nodulation gene expression of Rhizobium can be used to preliminarily determine the interaction between Rhizobium-legume green manure and crop plants.A suitable method for providing Rhizobium-legume green manure in the system.Rhizobium-legume green manure and tea intercropping can increase soil organic matter and total nitrogen,enrich soil microbial population diversity,increase soil pH value,provide a good soil environment for tea tree growth,and legume green manure during flowering the effect of returning to the field was the best.In addition,leguminous green manure has the best effect of turning over and returning to the field at the blooming stage,initially achieving the effect of reducing the application of chemical nitrogen fertilizer in the tea garden.