Effect of biological disinfestation on soil improvement, Ralstonia solanacearum suppression and tomato growth

Soil-borne diseases and soil degradation caused by continuous cropping or monoculture restrain the sustainable development of agriculture. Chemical soil fumigation is the most popular method used to control soil-borne diseases in terms of cost and efficacy, but its negative impact on the environment raises a significant concern. Biological soil disinfestation (adding organic materials in soil and mulching for certain time, BSD) is widely used as alternative improvement of degraded soils and in preventing the occurrence of soil-borne diseases. To solve the problems associated with continuous cropping and the soil degradation caused by the intensification of monoculture, the effects of BSD on soil properties, bacterial wilt control and tomato growth were determined in soil incubation and field experiments. There were four treatments in the experiment — the control (CK), BSD with 2% rice bran, wheat bran and tea seed bran. The results showed that different BSD treatments had no significant effect on soil total P and K content, but significantly increased soil temperature, pH, electric conductivity and contents of organic matter, total N, available N and available K. Contrarily BSD treatments significantly reduced soil Eh and the amount of Ralstonia solanacearum in the soil by 97.27%-99.14%. BSD treatments reduced the incidence of bacterial wilt by 29.41%-42.65%, which in turn enhanced tomato plant resistance against the disease. In addition, BSD significantly increased chlorophyll fluorescence parameter F_v/F_m of tomato leaves, but it had no significant effect on net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO₂ concentration. BSD treatments increased tomato yield by 41.41%-56.25%, and the ratio of sugar to acid and soluble sugar content of tomato fruits. Among different organic materials, BSD with wheat bran had the best effect in terms of soil improvement, yield increase and bacterial wilt suppression. In summary, the potential of BSD was promising for the improvement of soil, prevention and control of soil-borne bacterial wilt disease and promotion of tomato growth. Thus BSD was critical for a non-chemical disinfection of cultivated soils.