| Tobacco continuous cropping effected the yield and quality of tobaccoseriously, this test is main to resarch the effect of tobacco continuous cropping on thesoil enzyme activities, carbon content, microorganism diversity, utilization ability ofcarbon resource. Soil samples were collected and determinedfrom continuouscropping1～5year tobacco fields in Henan and Chongqing.The test was a partresearch of soil health mechanism, and can provide new ways for the sustainable useof soil and the control of soil-borne diseases,provide theory according for amend soilhealty condition. The results were as follows:1. On the condition of continuous cropping1～5years, the soil enzyme activitiesand SOC content changed significantly. Meantime, the activities of soil amylase,sucrase and pectase cellulase and SOC content increased and then decreased down toa lower level. and showed a summit at2～3continuous cropping year, but the above4index decreased significantly over3years and were obvious lower than1year, Theobtained results revealed that the disease index of tobacco bacterial wilt and tobaccoblack shank were higher as a longer continuous cropping years, the results alsoindicated that there existed a negative relationship between the disease index and SOCcontent, activities of soil amylase, sucrase, pectase cellulase as a whole.2. The soil microorganism diversity of different continuous cropping years weredetermined by PCR-DGGE technology, the results indicated that the PCR results oftobacco soil bacterias and fungus of different continuous cropping years of chongqingand henan were not significant, but the DGGE fingerprint showed that two and threecontinuous cropping years were better than the other treatments, this indicated thatshort-term continuous cropping was beneficial for increasing the tobacco soilmicroorganism diversity.3. Methanotrophs is a kind of microbe which can use methane as their onlycarbon and energy sources, methanotrophs is very important in carbon cycle. Theresults of test indicated that the methanotrophs MOB II were richer than MOB I ofdifferent continuous cropping years of chongqing and henan, The bands location andmounts of MOB I DGGE fingerprint of chongqing and henan had a obsolete difference duringdifferent continuous cropping years, this means that the continusous cropping had a minoreffection. The bands location and mounts of MOB II DGGE fingerprint of chongqing and henanwere not absolute sameness, its mounts and brightness were both better at continuous cropping3 years, this means the short-term were good for increase the diversity of soil methanotrophs MOBII.4. Effect of continuous cropping on soil microorganism mechanis is one ofresearch hot spots at present, the effect of continuous cropping on soil microorganismactivities were analysed at the metabolic physiology level by using BIOLOG. Thetobacco soil from chongqing and henan were analysed and the results indicated:(1)The average well color development(AWCD) of soil microorganism were significanthigher at short-term continuous cropping(continuous cropping years≤3years) than4and5years, this reflected that soil microorganism activities were still high atshort-term continuous cropping;(2) The species diversity and species relative densityof soil microorganism were significant higher at short-term continuous cropping, thehyperspace diversity of species community of chongqing and henan had the similarlaw as a whole, the difference of common species of microorganism community wasnot significant;(3) The results of principal component analysis(PCA) indicated thatcarbohydrates, carbohydrates and carboxylic acids which were the main carbonresources were utilized by soil microorganism of tobacco continuous cropping, thesoil microorganism had a higher utilization rate of carbon resource at short-termcontinuous cropping. The synthetical study indicated that the soil microorganismactivities were higher at short-term continuous cropping, and sharp decline at4and5years. |
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