| Based on the actual of Luohe tobacco production in Henan province,we did research on soil in Luohe Tobacco Science Park.Yuyan 10 was used as cropping material,and we studied the soil conditions and tobacco quality of different continuous tobacco cropping years including the effect of soil nutrient changes,the soil enzyme activity,the quality of flue-cured tobacco and the root microbes.We complete root microscopic analysis of biological diversity through the DGGE(modified gradient gel electrophoresis)on soil samples analysis of bacteria and fungi.The main results were as follows:1.The flue-cured tobacco soil of rotation(corn as before),continuous cropping for 3 and 6 years were studied for the soil nutrients variation situation,and the results on the whole showed that available nitrogen and available potassium of the continuous cropping for 3 years was more than cropping rotation and 6 years continuous cropping in the period of vigorous growth and the mature stage,so short-term continuous cropping can increase the content of soil nitrogen and available potassium,while they will decrease by the trend of long-term continuous cropping;in the period of vigorous growth and the mature stage the content of soil available phosphorus will accumulate with the continuous cropping years.Also in the period of vigorous growth and the mature stage,the soil organic matter of cropping rotation was greater than the continuous cropping as a whole,and it reduced as continuous cropping years increasing,so continuous cropping decreased the content of organic matter in soil,and fertility declined.2.According to the change of soil enzyme activity,the results as a whole,the cropping rotation for soil invertase and alkaline phosphatase activity was greater than continuous cropping thus explained the continuous cropping decreased the two enzymes,and the soil urease activity showed that continuous cropping for 3 years was the largest,continuous cropping for 6 years was the lowest,it may be liked to short-term continuous cropping increasing nitrogen while long-term continuous cropping decreasing nitrogen.For protease activity in resettling stage and the period of vigorous growth,continuous cropping affected little.3.The flue-cured tobacco was analyzed for physical properties,chemical components and neutral aroma components,the results showed that 3 years continuous cropping tobacco was suited to improve the filling power as its thinner identity.Specifically,continuous cropping for 3 years was significantly higher than cropping rotation and 6 years continuous cropping for filling power and stem ratio,it may be due to the thinner identity for 3 years continuous cropping,cropping rotation >6 years continuous cropping>3 years continuous cropping for leaf thickness as well;tension resistance showed that cropping rotation significantly larger than continuous cropping,and there was no significant difference between 3 and 6 years;leaf specific weight of six years continuous cropping and cropping rotation was significantly more than 3 years of continuous cropping;and the rest of the index had no significant difference.For chemical composition,overall,compared with continuous cropping tobacco the cropping rotation of flue-cured tobacco was more coordinated,and 6 years continuous cropping was slightly better than that of continuous cropping for 3 years.Specifically,for reducing sugar,potassium content,total sugar,sugar-nicotine ratio,sugar-nicotine ratio,potassium-chlorine ratio,Shi Mu Ke value the cropping rotation was significantly more than 3 years of continuous cropping,and with the increase of continuous cropping years,they reduced firstly and then increased.Along with the increasing length of continuous cropping,the protein,nicotine,total nitrogen increased at first and then decreased,potassium content reduced at first and then increased;the trend of the chlorine had been reduced.In terms of neutral aroma components,phenylalanine group,browning products,cembratriendiol group,cropping rotation> 6 years continuous cropping > 3 years continuous cropping,and with the increasing length of continuous cropping,they decreased at first and then increased;for the contents of carotenoids degradation products and neophytadiene,6 years continuous cropping > 3 years continuous cropping> cropping rotation,and it showed the tendency of increase gradually with the increase of continuous cropping years.For the total amount(excluding neophytadiene),cropping rotation > 6 years continuous cropping > 3 years continuous cropping.4.The research was about the relationship between different continuous cropping years and planting tobacco soil microbial quantity,the results showed that the bacteria number of cropping rotation soil was larger than in continuous cropping soil as a whole,and 6 years continuous cropping was significantly more than 3 years continuous cropping in resettling stage and the period of vigorous growth,and the bacteria number reduced gradually along with the resettling stage,the period of vigorous growth and the mature stage;the fungi number of rotation to be less than the continuous cropping soil,6 years continuous cropping was significantly higher than rotation and 3 years continuous cropping and it had a maximum in resettling stage.And 3 years continuous cropping was significantly greater than the rotation and continuous cropping for 6 years in the period of vigorous growth and the mature stage,and it showed a trend of gradually less.Actinomycetes number showed rotation > 3 years continuous cropping> 6 years continuous cropping,and the resettling stage > the period of vigorous growth > the mature stage,and they three had significant differences during the resettling stage.5.The research on different continuous cropping of rhizosphere bacteria diversity showed that the electrophoretic bands in the period of vigorous growth(III-V1、III-V2、III-V3)were more visible,so the tobacco soil bacterial community is rich in the period of vigorous growth.Overall,bacterial population structure in cropping rotation,3 years continuous cropping and 6 years continuous cropping had little difference,this was using DGGE profiles do similarity analysis,getting the same results from bacterial community similarity index.It may be due to the rhizosphere bacteria of cropping rotation,3 years and 6 years continuous cropping was similar in the same area,the same soil texture and different flue-cured tobacco growth period,and the growth period of soil bacterial community is greater than the effect of continuous cropping on soil microbial communities.We did the research through the binding sort of RDA analysis of bacteria with the soil physical and chemical properties,the results showed that bacteria activity of Chloroflexi,Acidobacteria and Corynebacteriaceae had a strong impact on soil nutrition metabolism.6.Analyzing the rhizosphere fungi diversity of different continuous cropping,the research showed that flue-cured tobacco had rich fungi community in mature period by the electrophoresis figure and diversity index,but the treatment of fungal community difference is a little big,so continuous cropping changed the fungi community structure of flue-cured tobacco soil,which may be due to the continuous cropping soil root secretion,factors such as soil nutrient imbalance,cause of pathogenic fungus breeding.According to the RDA,Thanatephorus cucumeris,Pythiaceae,Mortierellaceae,Alternaria,Lagenidiaceae,Lagenidiaceae,Rhizoctonia,Fusarium and Xylariomycetidae had different degree of correlation with soil nutrient metabolism.In general,continuous cropping reduced the quality of flue-cured tobacco,broke the soil nutrient equilibrium and reduced the self-repairing capability of soil,largely changing the diversity of soil fungi community structure,but a smaller influence on the diversity of bacterial community structure.This paper analyzed continuous cropping soil,rhizosphere microorganisms and quality of flue-cured tobacco variation situation in Luohe flue-cured tobacco area,thinking that the cropping rotation can relisf the continuous cropping obstacles to a certain extent. |
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