| Tobacco is one of the important economical crops in China, while it is often destroyed by bacterial wilt, a devastating soil-borne disease caused by Ralstonia solanacearum, during the growth period. The disease affects the growth of tobacco seriously and causes great financial loss on the tobacco production. Traditional control methods are not always effective on controlling this disease, thus stimulating the development of biological control and soil amendments to control bacterial wilt. The disease can decrease the yield and quality of tobacco, and the application of biological control and soil amendments may also affect the yield and quality of tobacco, which determine the production value of tobacco and income of farmer. Thus, it’s important to take the yield and quality of tobacco into account when applying the biological control and soil amendments to control bacterial wilt. Therefore, this experiment explored the influences of 3 kinds of bio-fertilizers on the control efficiency of bacterial wilt, growth of tobacco and tobacco chemical compositions in the soil condition with or without limestone in a field, where the bacterial wilt occurred severely in the region of Pengshui, Chongqing municipality. Meanwhile, the effects of different treatments on the chemical properties of soil and the amount of R. solanacearum were analyzed as well. The objectives of the study were to choose an effective combination of bio-fertilizer and soil amendment suitable for the growth of tobacco in this area and to provide the theoretical basis on researching the field conditions, mechanisms analysis on inhibiting R. Solanacearum by soil conditioner further and the application of bio-fertilizer reasonably. The main results of the paper as below:1. Bio-fertilizers are more effective to control bacterial wilt with the application of limestone than the treatments without limestone. Compared with the control treatment, B1 is the most effective fertilizer to control the disease among 3 kinds of bio-fertilizers, and it is the optimum control with limestone, which is better than other treatments significantly. After 60 days and 90 days of tobacco growth, the disease incidence of this optimum treatment is just 9.2%, and not higher than 40%, respectively. The number of R. solanacearum in soil treated by different bio-fertilizers is lower obviously than control treatment. B1 treatment is the optimum among bio-fertilizers, which decreases two order of magnitudes compared with control treatment. Furthermore, limestone added to soil can further decrease the amount of R. solanacearum. The amount of pathogen is in line with the disease incidence in field.2. Bio-fertilizers added to soil without limestone can change the soil chemical properties significantly. The content of available P (except B2), alkeline-N and available K in soil with bio-fertilizers are all higher than the control soil markedly. The alkeline-N content increase about 6.2%～11.5%, and the content of available K in soil with B1 increase the most about 28.87% compared with that in control soil. The treatments with limestone decrease the soil alkeline-N and available K content compared with the treatments without limestone, while increase available P and improve soil pH about 1.0～1.8 units compared with initial soil pH.The results of correlation analysis between soil chemical properties and disease incidence (90 days) show that only available P is significant negative correlation with disease incidence, and neither available K nor alkeline-N has the correlation with disease incidence.3. The effects of different bio-fertilizers on the growth of tobacco are not significant in the soil with or without limestone. Compared with the control treatment, bio-fertilizers play positive role in improving the growth of tobacco.4. The effects of bio-fertilizers on tobacco chemical compositions in different part of tobacco leaves are not evident, and the change tendency has non-regularity. However, the quality of middle leaves is better than that in top and bottom part as a whole, and the content of nicotine in upper leaves and total sugar content in bottom leaves are not within the comfort zone. The content of N and K in top leaves are higher than middle and bottom leaves in each plot, and B1 can add the content of N and K. significantly in top leaves up to 31.07%,25.68% respectively compared with the control treatment, while the difference of N, K content in middle and bottom leaves are not obviously. The addition of limestone to soil has no evident effect on the tobacco leaves content of N and K content, but the change tendency of content of P in different part of leaves is not obvious. Bio-fertilizers can increase the content of total sugar and reducing sugar in top leaves, and the treatment effect is that B2>B1>B3, furthermore, the nicotine content is decreased in top leaves and increased in middle and bottom leaves conversely. The plots treated with limestone at first, showing that bio-fertilizers lower the content of total sugar and reducing sugar in bottom leaves, and increase the content of nicotine in middle leaves, which is still within the comfort zone, while the effect is small on the top and bottom leave nicotine content.5. Bio-organic fertilizers have a positive promotion effect on increasing tobacco economical benefit. The tobacco yield and production value in the plot treated with B1 is higher than that treated with B2 or B3, and increase about 26.34%,48.22% respectively compared with the control treatment. The average price and ratio of superior and medium tobacco in the plot treated with B1 and limestone exceed that in the plots treated with other treatments, and increase about 18.55%, 22.01% respectively compared with the control treatment. Through the data analysis, the results show that soil available K content has a significant positive correlation with each economical index of tobacco. |
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