Effects Of Rotation And Continuous Cropping On Potato Growth And Rhizospheric Microenvironment

In poverty-stricken areas of China,potato is a dominant crop for promoting food production and getting rid of poverty.Due to a limited farming area and intensive potato production therein,mono-cropping is prevailing in these areas.However,long-term mono-cropping may reduce soil microbial community diversity and change the community structure,disturbing the balance of soil nutrients in ratio,thus affecting potato growth and yield.Although a large number of studies have demonstrated that rotation is an effective practice to alleviate the impact of mono-cropping on the soil,so far little has been reported on how the rotation of potato with quinoa or maize influenceing microenvironment of the rhizospheric soil of potato and interactions between soil and the root system.So this study was going to investigate the influence and its mechanism of continuous potato cropping and rotation with quinoa or maize on soil microbial community,soil quality,potato growth and yield,so as to provide a theoretical support to remove the obstacle of mono-cropping in potato production and build a better rotation model for those areas.The main conclusions were as follows:?1?Rotation of potato with quinoa or maize had a significant effect on the soil bacterial community structure.Compared with continuous cropping,rotation of quinoa or maize significantly increased the Chao1 index,ACE index and Shannon index of bacteria in the rhizospheric soil.The relative abundance of Proteobacteria,Acidobacteria,and Gemmatimonadetes in the soil treated by rotation increased significantly compared to continuous cropping,while the relative abundance of Actinobacteria decreased significantly.After potato field rotation,the relative abundances of rhizospheric soil bacterial dominant genera such as Sphingomonas,Gemmatimonas,Pyrinomonas,Aridibacter and Lysobacter were significantly increased.Compared with continuous cropping,these genus in soil treated by rotation of quinoa increased by 28.98%,2.79%,35.96%,28.86%and 166.49%,respectively,and rotation of maize increased by 70.40%,11.57%,56.54%,42.18%and 90.37%,respectively.After rotation,most of the functional bacteria related to C and N?Pseudolabrys,Sphingobium,Nocardioides,Arenimonas,Gaiella,etc.?were significantly increased in relative abundance.?2?Compared with bacteria,rotation of potato field with quinoa or maize had a greater impact on soil fungal community structure.Compared with continuous cropping,rotation of quinoa or maize significantly increased the diversity index?Simpson,Shannon?and richness index?Chao1,ACE?of rhizospheric soil fungal community.The relative abundance of Ascomycota in the continuous cropping potato rhizospheric soil was absolutely dominant;the relative abundance of Ascomycota in rhizospheric soil of rotation treatment was significantly lower than that of continuous cropping,while the relative abundance of Basidiomycota was significantly increased.Among the dominant genera of fungi in the rhizospheric soil of each treatment,Madurella,Colletotrichum and Clitocybe only exist in the soil of continuous cropping potato,rotation of quinoa and rotation of maize,respectively;The relative abundance of Mortierella and Chrysosporium in rhizospheric soil of rotation treatment were significantly higher than that of continuous cropping,while Gibberella and Fusarium were significantly reduced.After potato field rotation,the relative abundance of most of the potential beneficial bacteria?Metarhizium,Chaetomium,Mortierella,Clonostachys,Penicillium,etc.?in the soil were significantly increased,while most of the potential pathogenic bacteria?Gibberella,Fusarium,Alternaria,Sarocladium and Ustilago,etc.?were significantly reduced.?3?Rotation of potato field with quinoa or maize reduced soil pH value in potato rhizosphere significantly,increased the contents of organic matter,alkalyzable nitrogen and available phosphorus,enhanced activities of soil enzymes,decreased fungi population,increased the number of soil bacteria and actinomycetes,and the ratio of bacteria and fungi?B/F?,and improved soil properties and promoted potato growth,which was enbodied to some extent in plant height,stem diameter,shoot dry weight,root dry weight and yield of potato tuber.Rotation of potato with quinoa or maize increased the activities of SOD,POD and CAT in potato root system,decreased the producing rate of O₂.^-and the content of MDA,increased the content of osmosis regulating substances.All the findings indicated that the rotation relieved the stresses of mono-cropping on potato plants.And rotation of potato with quinoa or maize also increased the total length,surface area,volume,mean diameter and tip number of potato roots significantly.In general,rotation of potato with quinoa or maize promoted the growth and development of potato roots,which corresponded to the improvement of physical,chemical and biological properties of the soil and the development of the shoots of potato as well.To sum up,comparison between the two rotation patterns showed that the rotation of potato with maize was better than that with quinoa in alleviating the adverse impacts of mono-cropping.