Study On Yield And Efficiency Increasing Mechanism Of The Mixed Planting Mode Of Alfalfa And Orchard Grass In Different Row Ratios

Mixed sowing of alfalfa(Medicago sativa)and orchard grass(Dactylis glomerata)can make full use of various natural resources,better play to the production potential of mixed grassland to achieve higher yieldincreasing effect and ecological effect.Exploring the mechanism of increasing yield and efficiency of mixed grassland from the perspective of plant,soil and microbial interaction is helpful to the construction of mixed grassland.In this study,alfalfa and orchard grass were used as materials,and the field mixed sowing test and pot simulation test were combined.The field mixed experiment was designed to explored the optimal mixed sowing mode of alfalfa and orchard grass from the perspective of plant,soil and microbial interaction through mixed sowing planting and high-throughput sequencing.The pot experiment verified the changes of microbial diversity and the influence of mixed sowing mode on soil by sximulating mixed sowing and dilution reduction method.The results are as follows:(1)Mixed sowing significantly increased the yield of mixed grassland.Compared with monoculture grassland,alfalfa and orchard grass row ratio 1:1 mixed sowing(A1O1),alfalfa and orchard grass row ratio2:2 mixed sowing(A2O2),alfalfa and orchard grass peer mixed sowing(MSR)increased by 27.59%,58.57%and 16.45%,respectively.The yield effect of A2O2 treatment was the best.Mixed sowing significantly increased the yield,nutritional quality and feeding value of alfalfa.It improved the nutritional quality of orchard grass and had no significant effect on the yield of orchard grass.Alfalfa is the dominant plant in mixed grassland,and interspecific competition is greater than intraspecific competition.(2)Mixed sowing affected soil physical and chemical properties,changed the composition of rhizosphere soil microbial community structure,and increased Alpha diversity of microbial community.The A1O1 mixed sowing model had high ecological benefits.Mixed sowing changed the proportion of other metabolic functional genes in alfalfa bacterial community,reduced the proportion of functional genes related to nitrogen metabolism cycle,increased the metabolic functional genes of small molecular compounds in orchard grass bacterial community,reduced the metabolic functional genes of macromolecular compounds,reduced the harmful fungi in orchard grass rhizosphere soil,and improved the rhizosphere soil environment of orchard grass.(3)There were significant differences in plant,soil and microbial interactions between alfalfa and orchard grass.The physical and chemical properties of plants and rhizosphere soil were positively correlated with fungi related indexes.The physical and chemical properties of plants and rhizosphere soil were negatively correlated with bacterial related indexes.(4)Changes in microbial diversity have different effects on plant-soil feedback.A large loss of microbial diversity will affect rhizosphere soil nutrients and soil extracellular enzyme activities,and mixed sowing weakens the effects of microbial diversity loss on rhizosphere soil nutrients and soil enzyme activities.The soil with high microbial diversity showed stability,and the soil with low microbial diversity was more susceptible to environmental changes,and showed differences after the community structure gradually stabilized.In summary,the mixed sowing of alfalfa and orchard grass increased forage yield,affected soil physical and chemical properties,rhizosphere soil microbial structure composition and functional diversity.The yield increase benefit of A2O2 was the best,and the ecological benefit of A1O1 was the best.The interaction among plants,soil and microorganisms is the reason for increasing yield and efficiency of mixed grassland.Microbial diversity affected the physical and chemical properties of rhizosphere soil and soil extracellular enzyme activity.Mixed sowing weakened the impact caused by microbial diversity loss.The soil with low microbial diversity was more vulnerable to environmental changes.