The Alleviation Mechanism Of Tobacco-garlic Rotation And Interplanting On Soil Continuous Cropping Obstacles

The long term successive plantation of the flue-cured tobacco can easily lead to continuous cropping obstacles.With widely application in the tobacco planting areas,the rotation and interplanting of tobacco and garlic have great advantage in reducing plant diseases and insect pests,and alleviating the reduction of tobacco yield and quality,thuspromoting soil production.In this study,a 3-year field experiment was conducted in an area with 2-year successive plantation of the flue-cured tobacco to monitor the changes of soil physical and chemical properties,enzyme activities,and microbial diversity and quantity with three cropping systems of rotation,interplanting and monocropping of tobacco.Meanwhile,the changes of soil microbial community structure were also investigated by the technologies of phospholipid fatty acid(PLFA)and denaturing gel gradient electrophoresis(DGGE).The results were as follows.(1)The tabacco yield of monocropping system decreased with the increasing planting ages,and was significantly higher than that of rotation and interplanting system.In the 3rd year,the tabacco yield of rotation and interplanting system were 1.87 and 1.50 times as much as that of monocropping system.The nitrogen concentrations in tobaccos of monocropping system were significantly higher than those of rotation and intercropping system from the 1st to the 3rd year.The phosphorus and potassium concentrations in tobaccos of rotation and interplanting system were significantly higher than those of monocropping system.In the 3rd year,the potassium concentrations in tobaccos of rotation and interplanting system were 1.16 and 1.23 times as much as those of monocropping system.The starch and reductivesuga concentrations in tobaccos of monocropping system were lower than those of rotation and interplanting system.The total sugar and chlorine concentrations in tobaccos of monocropping system were higher than those of rotation and interplantingsystem.The nicotine concentrations in tobaccos of monocropping system were 1.34 and 1.13 times,and 1.45 and 1.27 times as much as those of rotation and interplanting systemin the 1st year and 2nd year.(2)The nitrogen and potassium concentrations in tobaccos of monocropping system at the mature stage were lower than those of rotation and interplanting system.In the 3rd year,the nitrogen and potassium concentrations in upper leaf of rotation and interplanting system at the mature stage were 1.36 and 1.54 times,and 1.33 and 1.66 times as much as those of monocropping system.With the increasing planting ages,the phosphorus concentrations in upper leaf of monocropping system were lower than those of rotation and interplanting system.There was no significant difference among the iron concentrations in middle leaf of monocropping,rotation and interplanting system at the mature stage.In the 3rd year,the manganese concentrations in tobaccos of monocropping system at the mature stage were lower than those of rotation and interplanting system.With the increasing planting ages,the copper concentrations in tobaccos of monocropping system were higher than those of rotation and interplanting system,while the zinc and boron concentrations in tobaccos of monocropping system were lower than those of rotation and interplanting system.In the 3rd year,the zinc concentrations in in tobaccos of rotation and interplanting system at the mature stage increased by 24.53%and 7.22%,12.45%and 37.42%,and 36.18%and 81.40%for the lower leaf,middle leaf and upper leaf,respectively.(3)In the 1st and 3rd year,the rhizosphere soil pH of rotation and intercropping system were higher than that of monocropping system.In the 3rd year,the rhizosphere soil pH of rotation and intercropping system at the mature stage of upper leaf increased by 0.27 and0.14 compared with that of monocropping system.With the increasing planting ages,the total nitrogen,available nitrogen,available phosphorus and available potassium in the rhizosphere soil of rotation and intercropping system at the mature stage were higher than those of monocropping system.The total nitrogen in the rhizosphere soil of rotation and intercropping system at the mature stage of upper leaf were 1.02 and 1.29 times,1.37 and 1.74 times,1.21 and 1.03 times as much as that of monocropping system at the 1st,2nd and 3rd year,respectively.In the 3rd year,the available nitrogen,available phosphorus and available potassium in the rhizosphere soil of rotation and intercropping system at the mature stage of upper leaf increased by 9.77%and 6.74%,9.00%and 26.87%,and 10.99%and 4.71%compared with those of monocropping system.(4)The activity of acid phosphatase and urease in the rhizosphere soil of monocroppingl,rotation and intercropping system increased with the increasing planting ages.The acid phosphatase activity in the rhizosphere soil of rotation and intercropping system was significantly higher than that of monocroppingl system among the whole growth stages.In the 3 rd year,the acid phosphatase activity in the rhizosphere soil of rotation and intercropping system at the mature stage of upper leaf was 1.11 and 1.11 times as high as that of monocroppingl system.The sucrose activity in the rhizosphere soil of rotation and intercropping system was higher than that of monocroppingl system among the whole growth stages.The activity of catalase and polyphenol oxidase in the rhizosphere soil of rotation and intercropping system was higher than that of monocroppingl system in the 3 rd year.The protease activity decreased with the increasing planting ages.In the 3 rd year,the protease activity in the rhizosphere soil decreased with the growth stages,and that of rotation and intercropping system was higher than that of monocroppingl system.(5)The bacteria population in the rhizosphere soil of rotation and intercropping system was higher than that of monocroppingl system among the whole growth stages from the 1st year to the 3rd year.In the 3rd year,the bacteria population in the rhizosphere soil of rotation and intercropping system increased by 3.20%and 11.25%at the mature stage of middle leaf and upper leaf,compared with that of monocroppingl system.Some difference wasobserved among fungi population in the rhizosphere soil of monocroppingl,rotation and intercropping system for different planting ages.In the 3 rd year,the fungi population in the rhizosphere soil of rotation and intercropping system at the mature stage of upper leaf was higher than that of monocroppingl system.The population of actinomycetes in the rhizosphere soil of rotation and intercropping system at the mature stage of middle leaf and upper leaf was higher than that of monocroppingl system for different planting ages.For all planting ages,the population of phosphate solubilizing bacteria and potassium bacteria in the rhizosphere soil of rotation and intercropping system were significantly higher than those of monocroppingl system,except those at the mature stage of lower leaf in the 1st year.In the 3rd year,the population of phosphate solubilizing bacteria and potassium bacteria in the rhizosphere soil of rotation and intercropping system were 1.08 and 1.13times,and 1.05 and 1.04 times as much as those of monocroppingl system at the mature stage of upper leaf.(6)According to the analysis of PLFA and DGGE,there was significant difference among the population of the 27 markers of soil microbes in the the rhizosphere soil of monocroppingl,rotation and intercropping system.At the mature stage,the total PLFA,bacteria,actinomycetes and protist in the rhizosphere soil of rotation and intercropping system were significantly higher than those of monocroppingl system.The bacteria community richness,species evenness and diversity index in the rhizosphere soil of rotation and intercropping system were higher than those of monocroppingl system at the mature stage of middle leaf and upper leaf,except those at the mature stage of lower leaf.The correlation analysis demonstrated that there was significant or highly significant correlation between available nitrogen,available phosphorus and tobacco yield.Significant or highly significant correlation was also observed between total nitrogen,organic,available nitrogen,protease activity and soil total PLFA.Besides,the available potassium showed a significant negative correlation with the protease activity in the rhizosphere soil.