Effects Of Banana And Sweet Potato Intercropping On Soil Microecology And Banana Growth And Development

Banana is a popular fruit among consumers and an important economic crop in tropical and subtropical regions.The traditional banana planting system is mainly based on perennial continuous monoculture,resulting in the decline of soil nutrients,the imbalance of nutrient elements,the deterioration of physical properties such as soil bulk density and aggregates,the accumulation of plant autotoxic substances,the imbalance of soil microbial diversity,the increase of pathogenic microorganisms,and the occurrence of diseases and insect pests.It will exacerbate the problem of continuous cropping obstacles,especially the occurrence of banana fusarium wilt,which will bring huge losses to the banana industry.Intercropping pattern has a positive effect on improving continuous cropping obstacles.In order to change the planting pattern of banana in successive years,two planting methods of banana and sweet potato intercropping and banana monoculture were set up with Guijiao No.1 as material in this paper.The effects of banana and sweet potato intercropping on soil temperature and humidity,soil nutrients,soil microorganisms,soil physical properties,soil enzyme activity,banana growth and yield were studied.To provide theoretical basis and technical support for improving the planting mode of banana and reducing the harm of diseases and insect pests.The main results are as follows:（1）The effects of banana and sweet potato intercropping on soil temperature,humidity and soil nutrients were as follows:The intercropping of banana and sweet potato can regulate soil temperature and increase soil moisture.From May to November,the soil temperature of5cm～20cm intercropping in summer is 0.46℃～4.55℃lower than that of monoculture,and the soil temperature of 10cm and 20cm intercropping in autumn is 0.37℃～0.97℃higher than that of monoculture.The soil water content of 5cm～20cm soil layer of intercropping was1.42%～14.55%higher than that of monoculture.The intercropping of banana and sweet potato had a positive effect on the content of main nutrients in soil.Compared with monoculture,the contents of organic matter,total nitrogen,total potassium,available nitrogen,available phosphorus and available potassium in intercropping sweet potato soil increased by10.64%～37.11%、16.35%～32.04%、4.15%～9.55%、25.39%～32.15%、3.56%～8.29%、31.16%～171.04%,respectively,and the difference reached a significant or very significant level.In addition,the soil p H value of intercropping was 6.33～6.46,which was 1.66～1.84 higher than that of monoculture,and the difference reached a very significant level.（2）The effects of banana and sweet potato intercropping on the population and structure of soil microorganisms were as follows:From May to September,the intercropping sweet potato soil bacterial population,Ace,Chao1 and Shannon diversity indices increased by5.54%～28.67%,6.32%～28.26%,11.12%～25.92%and 3.77%～16.29%,respectively,compared with monoculture,and the differences reached significant or extremely significant levels.The population numbers,Ace and Chao1 indices of intercropping soil fungi were increased by11.79%～38.69%,5.64%～11.46%and 14.27%～40.43%,respectively,compared with monoculture,except for Chao1 in May,the difference was not significant,and intercropping in May and September The Shannon index of high is 12.24%and 7.57%higher than that of monoculture respectively.The relative abundance of proteobacteria,acidobacteria,bacteroides and gemmatimonadetes in intercropping soil increased by 67.92%,8.64%,64.37%and 327.76%on average,respectively,while that of actinobacteria and chloroflexi decreased by 12.62%and51.65%on average,respectively.The relative abundance of the six dominant populations of intercropping bacteria,AD3,Acidothermus,Elsterales,Acidobacteriaceae Subgroup 1,Conexibacter and WPS-2,was lower than that of the monoculture,while the relative abundance of Subgroup 6 and other populations was significantly or very significantly higher than that of the monoculture.The monthly average relative abundance of ascomycota,basidiomycota,mortierellomycota,rozellomycota,chytridiomycota and glomeromycota in intercropping soil was higher than that in monoculture,but did not reach the level of significant difference.The relative abundance of the dominant populations of Neocosmospora rubicola,Iodophanus carneus,Conocybe anthracophila and Coprinopsis clastophylla of intercropping soil fungi was significantly higher than that of monocropping,and the relative abundance of two populations of Saitozyma podzolica and Fusarium equiseti was significantly lower.The intercropping of banana and sweet potato can regulate the community structure of soil bacteria and fungi,reduce the dominant population of bacteria,and significantly increase the number and diversity of soil microbial population.（3）The effects of banana and sweet potato intercropping on the functional diversity of soil microbial community were as follows:From May to September,compared with monoculture,the AWCD value of intercropping soil microbial community increased by 76.86%～1436.30%,and the soil microbial community shannon,simpson and mcintosh index increased by9.18%～101.23%、1.58%～30.87%、52.45%～504.48%,respectively,and the difference reached a very significant level.However,the difference in evenness index is not significant.In addition,the intercropping of banana and sweet potato increased the variety and metabolic activity of carbon sources utilized by soil microorganisms.The metabolic activities of intercropping soil microorganisms to carbohydrates,amino acids,carboxylic acids,polymers,phenolic acids and amines increased by 1381.23%,921.77%,537.64%,992.57%,607.63%and 345.93%on average,respectively,compared with monoculture,with the differences reaching significant or very significant levels.There are great differences in the utilization efficiency of different carbon sources between intercropping and monoculture.Intercropping soil microorganisms use carbohydrates and amino acids as the main metabolic carbon sources,while monocropping uses polymers and phenolic acids as the main metabolic carbon sources.The amount of carbon source compounds used by intercropping soil microbial community increased by 9～28 species compared with monoculture,and the difference reached a very significant or significant level.principal component analysis showed that carbohydrates and amino acids were the main carbon sources to change the microbial diversity of banana and sweet potato intercropping soil.Intercropping banana with sweet potato can improve soil microbial community diversity and increase soil microbial community carbon source utilization species and activity,with the effect of significantly improving the functional diversity of soil microbial community.（4）The effects of banana and sweet potato intercropping on soil physical properties and enzyme activities were as follows:From May to September,compared with monoculture,intercropping can reduce soil bulk density and solid phase composition by 3.28%～9.97%and1.24%～3.76%,respectively,and increase soil porosity,soil liquid phase and soil gas phase percentage by 1.24%～3.76%,0.36%～6.39%and 0.88%～4.34%,respectively.For the structural composition of soil aggregates,intercropping sweet potato promoted the transformation of microaggregates to larger aggregates,increased the content of water stable aggregates of>0.25mm by 0.60%～21.69%,and decreased the content of water stable microaggregates of soil<0.25mm by 0.24%～22.47%,improving soil aggregate stability indexes and promoting the increase of soil aggregate stability.The soil sucrase,catalase,phosphatase and urease activities of banana and sweet potato intercropping increased by an average of 225.25%,268.90%,18.35%and 31.47%,respectively,and the difference reached a significant or very significant level.Therefore,intercropping banana with sweet potato can significantly improve the stability of soil aggregates,improve soil physical properties and significantly increase the activity of major soil enzymes.（5）The effects of intercropping between banana and sweet potato on the growth,development and yield of banana were as follows:From March to September,compared with monoculture,the contents of chlorophyll,soluble sugar and soluble protein in banana leaves intercropped with sweet potato increased by 5.58%,7.86%and 0.20%on average,respectively.Intercropping banana pseudostem height,pseudostem thickness,monthly leaf growth and leaf area of the top second expanded leaf increased by 7.86%,5.36%,2.83%and 11.56%on average,respectively.Intercropping banana fruit index,fruit finger length,fruit finger stem circumference,fruit finger weight and yield per plant increased by 4.82%,0.19%,2.87%,6.65%and 9.49%,respectively.The budding date of intercropping banana is four days earlier than that of monoculture.The fresh weight yield of above-ground part of sweet potato in intercropping was 37777.78 kg·hm^-2.The intercropping of banana and sweet potato promoted the growth and development of banana and increased the yield of banana per plant.