Effects of three different soil amendments on the number and metabolic function diversity of rhizospheric microorganisms of cucumber

Abstract:

[Background] Soil microbes play an important role in regulating plant growth, improving soil nutrient utilization rate and maintaining ecosystem stability. [Objective] To explore the structure diversity of the microbial community in cucumber rhizospheric soil under the in situ treatment of waste by earthworms and the treatment with desulfurization gypsum for soil improvement, and reveal the relationship between the number of soil microorganisms and microbial diversity indexes. [Methods] We determined the number of cultivable fungi, bacteria, and actinomycetes in the cucumber rhizospheric soils treated with three different amendments (T1–T3), and employed Biolog-ECO microplate method to study the metabolic functions of microbial communities. We then compared the number and metabolic function diversity between the in-situ treatment of waste by earthworms (T1), the treatment with desulfurization gypsum (T2), and the combination of the above two treatments (T3). [Results] The number of cultivable actinomycetes of T1 and T3 treatments was significantly higher than that of CK and T2, and that of bacterial and fungal colonies had no significant difference among treatments. The AWCD values of different treatments presented an upward trend, rising rapidly within 0–96 h and then slowly to the maximum. The AWCD values of T1 and T3 were higher than those of CK and T2. The AWCD, Shannon index, Simpson index, Pielou index, and McIntosh index all showed significant differences among treatments. Compared with CK, T1 and T2 had efficient carbon source utilization. The number of bacteria and actinomycetes had positive correlations with AWCD value, Shannon index, Simpson index, McIntosh index, and Pielou index (p<0.05 or p<0.01), while that of cultivable fungi was negatively correlated with AWCD value, Shannon index, Simpson index, McIntosh index, and Pielou index (p<0.05 or p<0.01). [Conclusion] Upon the in situ treatment of waste by earthworms, the soil can harbor more microbial communities with higher diversity and higher efficiency of carbon source utilization, which reveals the good performance of earthworms in the treatment of waste and the corresponding changes of ecological functions under the new cultivation mode. The findings of this study are expected to provide a theoretical basis for new cultivation modes.