Effects Of Cassava Continuous Cropping And Rotation On Soil Physical And Chemical Properties,microbial Community And Yield

Cassava is intolerant to continuous crops.Continuous cropping,especially multi-year continuous cropping,not only greatly reduces production,but also deteriorates the quality.Studying the mechanism of cassava continuous cropping obstacles and taking appropriate measures to alleviate and overcome the continuous cropping obstacles are important issues that need to be researched and solved in cassava production.After cassava continuous cropping,soil physical and chemical properties and soil microbial characteristics will change,which will affect the yield and quality of cassava.In this study,the positioning of continuous cropping and rotation were used.In 2014?2018,half of the same land was cropped for five years with cassava,and the other half was cropped with sweet potatoes,sugar cane,soybeans,corn,and cassava.Four cassava varieties(XX048,RS01,SC205,NZ199)as materials,comparing the structure of plough layer,nutrient status,enzyme activity,etc.of soil in continuous cropping and rotation,comparing soil microbial abundance,diversity,community composition,and agronomic traits such as cassava plant height and stem thickness And economic traits such as yield and quality were investigated and compared,and their correlations were analyzed to study the relationship between cassava continuous cropping obstacles and soil physicaland chemical properties,soil enzyme activity,and soil microbial structure.The results are as follows:(1)In terms of soil layer structure,during the growing period,continuous cropping increased the average volume of soil solid phase by 27.64%,and the average change of soil liquid phase volume,soil gas phase volume,soil relative humidity,soil non-capillary porosity/total porosity changed Small 32.77%,13.78%,27.71%,49.84%.Continuous cropping will cause undesirable changes in the structure of the soil plough layer,affecting the exchange of soil water,fertilizer,gas and heat.(2)In terms of soil nutrient status,continuous cropping reduced soil available N content,soil available P content,soil available K content,and soil organic matter content by an average of 22.02%,12.02%,35.70%,37.58%,and average soil pH during the growing period Increase by 6.31%.Continuous cropping reduces the effective nutrient content of the soil,leading to poor cassava growth.(3)In terms of soil enzyme activity,the activities of soil urease and catalase change irregularly during the growth period.Continuous cropping reduced soil invertase activity and soil phosphatase activity by an average of 56.16% and15.61%.Cassava continuous cropping has a certain inhibitory effect on soil invertase and soil phosphatase activities.(4)In terms of soil microbes,continuous cropping increases the abundance and diversity of soil bacterial communities and decreases the abundance and diversity of soil fungal communities,reducing the abundance of beneficial bacteria such as Rhizobium and Mortierella,but including beneficial bacteria there was no significant change in the predominant flora within.(5)In terms of the growth status of cassava,continuous cropping reduced the plant height,stem thickness,and leaf chlorophyll content of cassava by17.26%,19.22%,and 11.45% on average.Continuous cropping can make cassava grow worse.(6)In terms of cassava yield and quality,the number of roots per tube,root length,root thickness,root weight,root starch,soluble sugar,sucrose,and reducing sugar content of single crop cassava per plant were lower than that of rotation,and the yield of continuous cropping cassava was reduced by 45.79%,40.31%,43.97% and 32.20% compared with that of continuous cropping cassava from XX048,RS01,SC205,and NZ199,the differences between XX048,RS01,and SC205 were significant,and the average yield decreased by40.57%.The cassava yield was significantly positively correlated with soil available P content,soil organic matter content,soil invertase activity,cassavaplant height,cassava stem thick,root soluble sugar content,root sucrose content,root reducing sugar content,and number of roots per plant,these indicators can be used as references index for predicting and increasing cassava output.(7)The four cassava varieties will have certain differences in variety characteristics in response to continuous cropping obstacles.The soil tillage structure,soil available N content,soil available K content,soil organic matter content,soil pH,cassava stem thickness,leaf chlorophyll content of the four cassava varieties in continuous cropping and rotation were not significantly different,soil available P content,soil enzymes and cassava plant height were significantly different.In summary,this study systematically clarified the factors and their interrelationships that caused continuous cropping obstacles,and revealed the main reasons for the cassava continuous cropping obstacles,providing an important theoretical and technical basis for reducing and overcoming the cassava continuous cropping obstacles.