Study On Soil Microbial Of Properties In Protected Tomato Root Cirumference

Obviously, the excessive use of chemical fertilizer, unbalanced application of nitrogen, phosphorus and potassium, single crop variety and seriously continuous cropping were common in protected vegetable cultivation, which leading to some serious problems, such as lower utilization of soil fertilizer, decline in the quality of the ecological environment, serious pests and diseases, decrease yield and quality of vegetables. Soil microbiological characteristics is an important characterization of soil quality, and to some extent can reflect the soil fertility condition. This paper studied the effects of different tomato growth period, different fertilizer treatment, different continuous cropping years on protected tomato field physical and chemical properties, and microbiological characteristics. The main results were as follows:1. The microbiological characteristics of rhizosphere and surrounding soil was investigated at different growing period of tomato plants by combination of traditional plate-counting method and PCR-DGGE technology. Results showed that the rhizosphere effect of tomato plant for soil microorganisms was obvious, the number of culturable microorganisms was inversely proportional with the distance from the tomato root surface. During the whole developmental periods of tomato, rhizosphere and surrounding soil culturable microorganisms performanced that, bacteria and fungi number increased, actinomycete decline; DGGE profile indicated that the highest diversity of rhizosphere soil bacterial at the early flowering and blossoming stage, and the soil bacterial community structure was similar between them.2. Planting tomato significantly increased soil microbial biomass and soil enzyme activity. Tomato rhizosphere soil microbial biomass carbon and nitrogen significantly decreased respectively in the60days and40days after planting, increased gradually, after planting80days, reached the highest value and then decreased; during the whole growing period, tomato rhizosphere soil invertase, urease and neutral phosphatase activity first increased and then decreased, hydrogen peroxidase activity changing trend was increased-decrease-rising. Tomato growth later stage, rhizosphere soil microbial biomass and soil enzyme activity decreased. Significant correlations between soil microbial biomass and invertase, urease and neutral phosphatase activity, but less correlation was found between microbial biomass and hydrogen peroxidase.3. The long-term application of organic manure combined with or without chemical fertilizer can significantly improved the greenhouse tomato field soil organic matter and nutrient contents, improved soil physical and chemical properties, reduced soil acidification process. Except total nitrogen, the content of soil nutrient was more decreased with the increased inorganic nitrogen fertilizer application.Long-term partial application of inorganic nitrogen fertilizer has accelerated the decline in soil pH. Phosphate played an more important role in improving soil organic matter content than potassium.4. The Long-term application of organic manure significantly increased the soil enzyme activities and microbial biomass. Organic amnure and organic amnure combined with phosphate fertilizer could distinctly improved the activities of soil invertase and acid phosphatase. Compared with invertase and acid phosphatase, little effect of fertilization on soil urease activity. The treatments which used chemical fertilizer only microbial biomass carbon was higher than that of the control, but microbial biomass nitrogen was lower. The amount of nitrogen fertilizer and phosphate fertilizer significantly increased soil invertase and soil microbial biomass carbon. Balanced fertilization was more useful for soil microbial biomass increase. Soil enzyme activities and microbial biomass were decreased with the increasing input of urea.5. PCR-DGGE profiles of different fertilizer treatment showed that, application of organic fertilizer can improve the soil microbial quantity, increase the number of dominant species, increase the dominant population number, stable community structure; excessive application of nitrogen fertilizer could change the species of soil bacteria dominant populations; different kinds of chemical fertilizer or fertilizer combinations had no effects on soil microorganism community structure.6. Through research on the actual production facilities of continuous cropping protected tomato field found, the soil nutrient content increased with continuous cropping years increasing, differences in soil nutrient content of continuous cropping for7years,10years,15years and20years was not visible, in the actual production, the main factors which affecting soil fertility was not soil nutrient. Tomato continuous cropping for a certain number of years (15years), soil invertase, urease activity, microbial biomass, microbial carbon and nitrogen ratio was upward trend, neutral phosphatase and catalase activity decreased, but various years of continuous cropping soil enzyme activity and microbial biomass difference was not big. Tomato long-term continuous cropping (20years), soil enzyme activities and microbial biomass decreased significantly.7. The effects of protected tomato continuous cropping on rhizosphere soil microbial community diversity was studies with PCR-DGGE technology. Results showed that soil indigenous bacterial community structure was significantly influenced by planting tomato under protected field, but soil bacterial community structure and diversity were not sensitive to continuous cropping years. Compared with soil indigenous bacteria, indigenous fungal community structure was more steady, but the dominant fungi were more different in the fields with different continuous cropping years, continuous cropping significantly decreased the number of some fungi, meanwhile, the number of some other fungi was significantly increased, most dominant fungi populations were enriched in soil with tomato continuous cropping years of20, and which number was quite different with the non-dominant fungi populations. The change of soil fungi population balance that caused by tomato continuous cropping maybe one of the important reasons for the tomato continuous cropping obstacle. Recycling and sequence analysis of prominent electrophoretic bands showed that the dominant bacteria of soil sample belong to Clostridium butyricum、Uncultured bacterium、 Bacillus and Arthrobacter, while the dominant fungus belong to Saccobolus dilutellus、 Uncultured fungus、Lasiobolus ciliatus、Spooneromyces laeticolor and Lasiobolidium orbiculoides.