Dynamics Of Forage Yield,Quality,Soil Nutrients And Bacterial Diversity In Rotation System Of Maize-ryegrass

In the context of the state’s efforts to develop grass husbandry,grain feeding and ag-ricultural supply-side structural reform,it is of great significance to promote the develop-ment and utilization of winter idle fields,to solve the current balance of grain and feed,and to accelerate the development of animal husbandry by using annual cold-season herbage,corn and rice rotation to develop grassland agriculture.Under the country’s vigorous de-velopment of grass and animal husbandry,grain reform and agricultural supply side struc-tural reform,it is of great significance to develop grassland agriculture by using winter fallow field to develop annual cold-season forage and maize and rice rotation,so as to promote the utilization of idle winter fallow field,and to solve the current grain and feed balance and accelerate the development of animal husbandry.In this study,annual ryegrass（Lolium multiflorum L.）was mixed with oat（Avena sativa L.）as the pre production part of forage production system of"annual ryegrass and forage maize",and forge maize（Zea mays L.）was used as the second part of forage production system.The yield and quality of forage grass were evaluated by the cumulative dry matter yield,the cumulative crude pro-tein yield and the cumulative digestible dry matter yield.The effect of mixed forage grass on the improvement of grass quality and yield was studied,and the superior mixed sowing combination and the suitable planting density of forage maize were selected to adapt to the annual mixed forage grass in Sichuan plain area.In addition,the former mixed forage grass and the later mixed forage maize soil were cultivated The productivity and the dynamic characteristics of bacterial community in the forage production system of"annual ryegrass and forage maize"were studied by the correlation analysis of the components,enzyme activity and the structure and composition of bacterial colony.The main results are as fol-lows:1.Optimal Sowing rate of annual ryegrass and common oat mixtures grasslandCombining the indicators of each index,it is found that M₁（annual ryegrass 22.5kg/hm²+common oat 37.5 kg/hm²）have a better feeding value,production performance of the forage,and complementary utilization of resources,the produced dry matter of19445.30 kg/hm²,crude protein of 2814.04 kg/hm²,digestive dry matter of 13135.30kg/hm².When all parameters considered,mixture with M₁ is the best common oat mix in-gesting combination for the artificial grassland of annual ryegrass in Sichuan agricultural region.2.The optimal previous crop treatment and planting density of forage maize（1）According to the yield and quality of forage maize,it is found that the perfor-mance of 78400 plants/hm² planting density was better than that of 60600 plants/hm²planting density;Among them,Y₀（common oat 150.0 kg/hm²）was the best treatment under the planting density of 78400 plants/hm²,followed by M₁.（2）The yield and quality of all parts and the whole plant of forge maize are different,and the utilization value of grain is the highest,and the rachis of spike is the worst.The dry matter yield and digestable dry matter yield from high to low is the Seed>stem>left>bract>corncb;the crude protein yield is the Seed>left>stem>bract>corncb.（3）The best rotation combination of"annual ryegrass and forage maize"rotation system was annual ryegrass（22.5 kg/hm²）+common oat（37.5 kg/hm²）,78400 plants/hm²of forage maize,with the hay yield of 50216.58 kg/hm²,crude protein yield of 5046.24 kg/hm² and digestible dry matter yield of 35422.61 kg/hm² is the best planting combination for forage production system of"annual ryegrass and forage maize"in Southwest China.3、Dynamics characteristics of soil nutrients and bacterial community in"annual ryegrass and forage maize"rotation system（1）The average relative abundance of soil bacteria in"annual ryegrass and forage maize"rotation system is as follows:Proteobacteria,Acidobacteria,Actinobacteria,Bac-teroidetes,Chloroflexi,Unclassified-proteobacteria,Unclassified-acidobacteria,Myxo-coccales,Rhizobiales,Sphingomonadales,Sphingomonas.（2）There are significant differences in the structure and function of soil bacterial community before and after systematic planting（P<0.05）.The relative abundance of soil bacteria in Proteobacteria,Acidobacteria and Chloroflexi increased with the advance of planting stage;the relative abundance of Rhizobiales,Sphingomonadales,Methylobacte-rium and Sphingomonas increased first and then decreased;while that of Firmicutes,Bac-teroidales,Clostridiales and Lactobacillus decreased all the time.The relative abundance of Cyanobacteria,Moniliformes,Lauria and cyanobacteria in different forage maize planting density was significantly different（P<0.05）.（3）The content of soil available phosphorus and soil urease activity were significantly correlated with the alpha diversity of bacteria（P<0.05）.Soil urease activity had the most significant effect on soil bacterial composition（P<0.05）.