Abstract
Application of soil amendments has been wildly used to increase soil pH and control bacterial wilt. However, little is known about causal shifts in the rhizosphere microbial community of crops, especially when the field naturally harbors the disease of bacterial wilt to tobacco for many years due to long-term continuous cropping and soil acidification. In this study, biochar (CP), lime (LM), oyster shell powder (OS) and no soil amendment additions (Control; CK) were assessed for their abilities to improve the soil acidification, change the composition of rhizosphere soil bacterial communities and thus control tobacco bacterial wilt. The results showed that oyster shell powder significantly increased soil pH by 0.77 and reduced the incidence of tobacco bacterial wilt by 36.67% compared to the control. The Illumina sequencing -based community analysis showed that soil amendment applications affected the composition of rhizosphere bacterial community and increased the richness and diversity. In contrast, the richness and diversity correlated negatively to disease incidence. Using LEfSe analyses, 11 taxa were found to be closely related with disease suppression, in which Saccharibacteria, Aeromicrobium, and Pseudoxanthomonas could be potential indicators of disease suppression. Our results suggested that the suppression of bacterial wilt after the application of soil amendments (especially oyster shell powder) was attributed to the improved soil pH and increased bacterial richness and diversity.
Highlights
Soil amendments are widely used in agriculture to increase soil pH and are considered to have positive effects on soil health and plant growth
The disease incidence in lime and oyster shell powder treatments decreased by 18.89 and 36.67%, respectively, but there were no significant differences between the biochar and control treatments
Soil amendments improved soil pH and reduced the occurrence of bacterial wilt High soil pH is especially important for controlling tobacco bacterial wilt (Zhang et al 2016)
Summary
Soil amendments are widely used in agriculture to increase soil pH and are considered to have positive effects on soil health and plant growth. The use of soil amendments as an alternative for bacterial wilt control has been studied. Earlier studies reported that a soil amendment composed of urea and calcium oxide (CaO) is effective for controlling bacterial wilt in tomato by affecting the pH and nitrite accumulation in the field (Michel et al 1997; Michel and Mew 1998). Tobacco bacterial wilt, which is caused by Ralstonia solanacearum, is a widespread and destructive soil-borne disease (Genin 2010). As is typical of soil-borne diseases, the occurrence and prevalence of bacterial wilt are closely related to soil quality. Soil acidification is closely related to bacterial wilt. Soil micro-ecology balance and microbial diversity are necessary to suppress plant soil-borne diseases
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