Study On The Changes Of Microbial Characters In Different Cropping Year's Greenhouse Soil

Changes of microorganism were the main reason that caused obstacle in continuous cropping in greenhouse cultivation. Based on the distribution of greenhouse cultivation in our country, research about soil in greenhouse and open field of Beiling in Shengyang province, Shouguang in Shandong province and Changzhou in Jiangsu province were studied. By investigating the state of greenhouse cultivation and analyzing the soil sample in these regions, characters of soil microbial biomass carbon, microbial biomass nitron, microbial biomass phosphorus and microbial activities in different cropping year's were revealed. And seasonal changes of soil microbial characters in Shuangliu Sichuan province where uncovering the shed in summer were researched too.The main results were as follows.1. The contents of soil microbial biomass in greenhouse were higher than in open field. The changes of soil microbial biomass showed clearly regulation with years. The contents of soil microbial biomass carbon and microbial biomass nitrogen changed similarly.The time of their maximum content appeared in four years cultivation, while the soil microbial biomass phosphorus showed the peak value after two years cropping.The study showed that increased available nutrients had different effects to microbial biomass.Increased available nitrogen was in favor of increasing the soil microbial biomass carbon, but the contents of soil microbial biomass nitrogen and microbial biomass phosphorus decreased. Compared with available nitrogen, increased available phosphorus just had the opposite effects to soil microbial biomass. The contents of soil microbial biomass carbon decreased quickly while soil microbial biomass nitrogen and microbial biomass phosphorus increased at this level. But all soil microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus declined with increased available potassium.2. In typical greenhouse cultivation area-Shouguang in Shandong province, compared with the open field soil, the contents of soil microbial biomass and the ratios between them changed obviously. The contents and amplitudes of soil microbial biomass were low and small in the open field soil, While this data about soil microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus, the ratio of soil microbial biomass carbon to organic carbon(MBC/OC), soil microbial biomass carbon to microbial biomass nitrogen(MBC/MBN) increased 92.18%,25.38%,276.05%, 17.54% and 61.71% respectively. And the ratio of soil microbial biomass nitrogen to total nitrogen(MBN/TN), soil microbial biomass carbon to microbial biomass phosphorus(MBC/MBP) dropped 53.02% and 31.29%.In addition to organic matter, available nitrogen, pH, the factors which affected the soil microbial biomass varied greatly also involved the ratio of soil microbial biomass carbon to organic carbon(MBC/OC), soil microbial biomass carbon to microbial biomass nitrogen(MBC/MBN), soil microbial biomass nitrogen to total nitrogen(MBN/TN) and soil carbon to nitrogen(C/N).3. Seasonal amount of microorganism changed obviously in greenhouse soil. The highest amount appeared in June, while December was the lowest. The amount of bacteria had the same characters as microorganism. The maximum amount of fungi, actinomyces and the content of soil microbial biomass carbon occurred in March.. Enzyme activities of urease, acid phosphatase, neutral phosphatase, invertase had the same features as diversity indices of microbial strains. They were highest in March and June was the lowest. Compared with the open field soil, the amount of microorganism, diversity indices of microbial strains, content of soil microbial biomass carbon and enzyme activities were higher in greenhouse. The percentage of actinomyces and fungi to microorganism were increased. Though the amount of microorganism and content of soil microbial biomass carbon reduced clearly, diversity indices of microbial strains, total enzyme activities were resumed after uncovering the shed.