| Continuous cropping obstacles, especially soil-borne diseases can cause serious harm to agricultural production, can be greatly reduced crop yields, limit the sustainable development of modern agriculture. Eggplant Verticillium wilts caused by Verticillium dahliae can hazards of serious soil fungi diseases in eggplant production. The traditional control method is the use of chemical pesticides for soil fumigation to kill all microorganisms in the soil result in a "biological vacuum" to combat soil-borne diseases. However, these traditional soil disinfectants not only undermine the ecological environment and affect the quality and safety of agricultural products, the effect is not ideal, there is an urgent need to find a safe, efficient, sustainable development, green soil disinfectant to combat Verticillium wilt on eggplant. Cyanamid type of fertilizer is not only a soil disinfectant, nitrogen fertilizer synergist, environmental protection agent, soil conditioner, is a truly multi-purpose insecticide and fertilizer. Lime nitrogen on Verticillium wilt on eggplant has a very good effect, but its control mechanism and optimal condition is not clear.In this paper, Verticillium wilt(Verticillium dahliae Kleb.) As representative of soil-borne bacteria, soil, planting eggplant for more than four years of continuous cropping obstacles, respectively, on two levels from the traditional artificial culture and molecular biology, cyanide ammonia fertilizer (calcium cyanamide and Dicyandi amide) cropping obstacles soil microecology and eggplant Verticillium wilt prevention mechanism and optimal condition. The main conclusions are as follows:1. Lime nitrogen alone application, can significantly with improve soil urease, invertase and cellulose activity of sex, reduce soil phosphatase activity, on the soil had catalase enzyme activity effect is not obvious; lime nitrogen with applied straw, can significantly improve soil ureaseperoxide, catalase and invertase activity, and reduce soil cellulase, and phosphatase activity. Dicyandiamide alone application can significantly improve the five kinds of soil enzyme activity; Dicyandiamide straw soil phosphatase activity was significantly higher than the control, significantly reducing soil cellulase activity of soil urease, catalase and invertase the impact of the activity is not obvious.2. Cyanamid fertilizers can significantly increase soil microbial biomass carbon and nitrogen content; straw on the soil microbial biomass carbon and nitrogen content influence is not obvious; the Cyanamid class Fertilizers with straw can significantly increase soil microbial biomass carbon and nitrogen content. Single application of lime, nitrogen can significantly improve the soil microbial respiration, dicyandiamide no significant effect; fertilizer straw, lime nitrogen to improve soil microbial respiration and dicyandiamide with the opposite trend.3. In the7days, the Dicyandiamide only at35℃Verticillium dahliae spore vitality inhibitory effect of lime nitrogen at25℃and35℃showed a significant inhibitory effect at10℃under a certain extent. The dicyandiamide no apparent inhibition of Verticillium wilt on eggplant mycelium growth, lime nitrogen have a good inhibitory effect on mycelial growth.4. Lime nitrogen can effectively improve even for the number of soil bacteria and actinomycetes, reducing the number of fungi, to improve the bacteria/fungi ratio (B/F) and actinomycetes/fungi ratio (A/F), change the soil microbialpopulation structure, to promote continuous cropping soil from fungal-led transformation led to bacterial imbalance in the microbial flora back to health, and thus play the role of prevention and control soil-borne diseases. Lime nitrogen fertilizer the straw would be more effective. The dicyandiamide there certain effect, but are not very satisfactory. PCR-DGGE results show that the cyanamide type of fertilizer to change the population structure even for soil bacteria and fungi, resulting in a number of new species and of dominant populations, also inhibit some populations; soil bacteria and fungi diversity index and richness. Lime nitrogen than dicyandiamide, even for changes in the microbial population structure of lime nitrogen with straw even for the microbial population structure to change the best.5. Using quantitative PCR technique to detect the number of Verticillium dahliae in the various soils. The results showed that rice straw had no inhibitory effect of Verticillium dahliae, and even significantly increased the number of bacteria. Dicyandiamide alone application, there is a certain degree of inhibition of Verticillium dahliae’in the first8days and20days of the inhibition rates were26.73%and32.23%; Dicyandiamide with straw to handle in the first8days significantly increased yellow wilt the number of bacteria,63.24%higher than the control, but significantly lower than the separate facilities straw processing; a certain degree of inhibition in the first20days, the inhibition rate was56.18%. Regardless of lime nitrogen fertilizer straw or not, in the first8days and20days can significantly reduce the number of Verticillium dahliae in the soil, inhibiting the rate of greater than or equal to99.90%.6. Lime nitrogen fertilizer straw suppression of Verticillium dahliae soil moisture conditions are60%or more of the moisture content of soil maximum water holding capacity; Optimum soil temperature is greater than or equals to25℃, the higher the temperature suppression the better; under different pH conditions, have a good inhibitory effect, soil partial alkaline effect. The greatest impact on soil moisture content and temperature on the effect of lime nitrogen and soil pH affect the second. Lime nitrogen fertilizer straw better stability.To sum up, lime nitrogen as a soil disinfectant, but also to the soil microbial growth and provide the nitrogen source, by changing the structure of microbial flora has a strong direct inhibitory effect on some pathogenic microorganisms, such as Verticillium dahliae, restore a healthy micro-ecological balance, improve the diversity and richness of the soil microbial to inhibit the development of pathogenic micro-organisms to provide a normal, healthy soil ecological environment for plant growth, this may be the main mechanism of lime nitrogen prevention and control of soil fungi diseases. This is also the advantage of lime nitrogen as a soil disinfectant, an important difference with the traditional chemical pesticides in soil disinfectant. |
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