Effects Of Cropping Patterns On The Ecological Characteristics Of Soil Microorganism Community And Quality Of Tobacco

To study the structure and function diversities of soil microbial communities, a 3-year fixed field experiment was carried out, using the methods of dilution plate culture, Biolog technology and soil chemical analysis to research the effects of different cropping patterns on the characters of microbial communities and soil nutrient. Combining the observation with the yield and quality of flue-cured tobacco, results shows as follows:The biomass of bacteria in continuous cropping cropland of tobacco was significantly lower than which under patterns of rotation cropping and alternate cropping, the average number of bacteria in continuous cropping cropland is lower than 20% of which under patterns of rotation cropping and alternate cropping, so was actinomycetes and fungus. With the continuous cropping years increasing, the biomass of bacteria is decreasing, which from 2007 to 2009 it fall off about 60%.The amount of actinomycetes is stable, which aboutl.5%-4.1% in total biomass of soil microbe. Fungus in continuous cropping cropland 14,16 showed significant ascent about 180% while 2007 to 2009. It means that, the proportion of rihzosphere fungus in soil microorganisms is increasing, and this observation indicates the degradation of soil fertility.The microbial activity of rizhosphere soil in continuous cropping cropland of tobacco is lower than it of alternate cropping pattern. Both of them fluctuating dramatically through the growth stages, and drop sharply in the stage of maturation. It shows that both of the two cropping patterns reduce the stability of rizhosphere microbial communities of tobacco, and exert negative effects on tobacco roots consequently. Of all the cropping patterns, rotation cropping is the most effective way to maintain microbial activity of rizhosphere soil of tobacco, of which the microbial AWCD is higher than it of continuous cropping and alternate cropping 37% and 114% respectively. Comparing the 3 types of the rotation cropping pattern, the microbial activity of I1 (soybean-wheat-tobacco) is the highest, and remain its livingness in the stages of rapid growth and maturation which have great impact on the yield and quality of tobacco. So we reckon I1 as the most adaptive approach of maintain the functional diversity of rizhosphere microorganisms.The soil under continuous cropping pattern has the highest pH, followed by rotation cropping, and pH of alternate cropping cropland soil is the lowest. The rank of average of soil moisture content is rotation cropping>continuous cropping>alternate cropping cropland. Organic matter content is an important indicator to measure soil fertility level, and nitrogen affect the development of tobacco plants, both of these ingredient in soil under continuous cropping pattern are significantly lower than the soil under the other two patterns. Available K content in roation cropping cropland is lower than continuous cropping and alternate cropping cropland. Available P content in soil of different cropping patterns resemble each other, the rank is continuous cropping> rotation cropping> alternate cropping cropland.The total sugar content in flue-cured tobacco of each cropping patterns is in the context of 27.69%-34.13%, which goes beyond the standard extension, and which rank as continuous cropping> rotation cropping> alternate cropping cropland. The contents of reducing sugars rank as alternate cropping> continuous cropping> rotation cropping cropland. Contents of nicotine, N, K, Cl and the ratio of N to nicotine in cured tobacco leaves of alternate cropping cropland are higher than the other cropping patterns, while the ratio of K to Cl is the lowest of the different patterns. And the ratio of reducing sugars to nicotine of cured tobacco leaves of continuous cropping cropland is slightly higher than others.Different cropping patterns determine the economic characters of flue-cured tobacco. Alternate cropping pattern lead to the highest yield, followed by rotation cropping pattern, continuous cropping pattern is the lowest, less than 200 kg/mu. Both of the proportion of high quality tobacco in continuous cropping and rotation cropping are more than 28%, which in alternate cropping pattern is 5.84%. And both of the average price of continuous cropping and rotation cropping reached 11 yuan/kg or above, which in alternate cropping pattern is 7.52 yuan/kg. Except which of alternate cropping pattern, the value of other two pattern reached more than 2200 yuan/mu. All of above, it shows that the pattern of alternate cropping has disadvantage of poor benefit, and the pattern of continuous cropping is difficult to maintain the yield of tobacco. So the conclusion is that rotation cropping pattern is the most adaptive approach.