Effects Of Rhizobium Inoculation On Nodulation Nitrogen Fixation And Nitrogen Utilization In Alfalfa-Elymus Mixed Sown Grassland

Based on the strain Sinorhizobium Meliloti XGL026,which had been screened for high nitrogen fixation rate and stress resistance in the previous work of this study,the colonization dynamics,competitive nodulation and nitrogen fixation effects of Rhizobium inoculated into alfalfa-elymus mixed seeding system under subsurface drip irrigation were studied by using the functional strain S.meliloti XGL026-GFP as reporter gene marker.The effects of nitrogen transfer and utilization and production performance provide a scientific basis for giving full play to the symbiotic and strong nitrogen-fixing function of rhizobium,building high-quality and efficient artificial mixed grassland,and improving grassland production capacity.It is of great practical significance to promote the sustainable development of agriculture and animal husbandry in Xinjiang.The main conclusions are as follows:(1)The colonization of labeled Rhizobium was detected by fluorescence detection,and the percentage of labeled Rhizobium was determined.Rhizobium inoculation in alfalfa-elymus mixed grassland increased nodulation number and nodule weight of Alfalfa in different stubble times and growth stages compared with non-inoculated alfalfa.Mixed seeding(alfalfa-elymus 1:2)inoculated with Rhizobium and nitrogen fertilizer(A1+E2+N+R)had the highest nodulation number,nodule weight,colonization of labelled Rhizobiura and the percentage of labelled Rhizobium in alfalfa,which was significantly higher than mixed seeding(A1+E2+R),single seeding with nitrogen fertilizer(A+N+R),and single seeding with bacteria(A+R).The number of nodules,nodule weight,colonization of labeled rhizobium,and the percentage of labeled Rhizobium in alfalfa-Elymus 3:7 mixed seeding inoculation(A3+E7+N+R,A3+E7+R)were significantly lower than that in alfalfa single seeding(A1+E2+N+R,A1+E2+R),but also lower than that in alfalfa single cropping(A1+E2+N+R),the number of nodules,the colonization of labeled Rhizobium and the percentage of labeled rhizobium.(2)Nitrogen fixation effect,nitrogen transfer rate,nitrogen transfer amount and contribution rate of biological nitrogen fixation were determined by 15N abundance method and 15N natural abundance hair method.The nitrogen fixation effect,nitrogen transfer rate and nitrogen transfer amount,biological nitrogen fixation contribution rate and soil nutrient content of alfalfa-Elymus mixed grassland inoculated with Rhizobium(A1+E2+R,A3+E7+R)were higher than those of non-inoculated alfalfa mixed grassland(A1+E2,A3+E7).Alfalfa-Elymus mixed sowing(1:2)inoculation plus nitrogen fertilizer treatment(A1+E2+N+R)and alfalfa-Elymus mixed sowing(3:7)inoculation plus nitrogen fertilizer treatment(A3+E7+N+R)increased the most.(3)The results showed that the inoculation of Rhizobium(A1+E2+R,A3+E7+R)on alfalfa-elymus mixed grassland promoted the growth of mixed grassland at different stages,increased chlorophyll content and yield of mixed grassland,increased crude protein content of alfalfa and elymus,decreased NDF and ADF content,and improved the quality of alfalfa.The increase of A1+E2+N+R in alfalfa-Elymus spp.mixed seeding(1:1)was the largest,which was significantly higher than that in mixed seeding(A1+E2+R,A3+E7+R),single seeding with nitrogen fertilizer(A+N+R)and single seeding with nitrogen fertilizer(A+R).The effect of alfalfa-Elymus spp.3:7 Mixed Inoculation(A3+E7+N+R,A3+E7+R)was not as good as that of alfalfa-Elymus spp.1:2 Mixed Inoculation(A2+E2+N+R,A1+E2+R).