Changes in soil quality, bacterial community and anti-pepper Phytophthora disease ability after combined application of straw and multifunctional composite bacterial strains

Abstract

Long-term implementation of intensive management in China has resulted in soil degradation and severe soil diseases. As the typical soil disease, pepper Phytophthora disease seriously affects the growth and development of many types of crops. To comprehensively address the problem of soil degradation and pepper Phytophthora disease, we have used a kind of novel multifunctional composite bacterial strains (MCBS) with excellent cellulose degradation and anti-pepper Phytophthora disease functions. In this study, we combined straw and this MCBS for the straw return experiment. The object of this study was to compare the influences of natural control without straw (CK), combined application of straw and MCBS (T1), and straw return under natural conditions (T2) on soil physicochemical properties, soil enzyme activity, soil bacterial community diversity, and soil anti-pepper Phytophthora disease (inhibiting the growth and reproduction of Phytophthora capsici that cause root rot, wilt, yellow wilt, vertical wilt, sudden collapse, black root, and stem rot of crops or reducing the negative impact from pepper Phytophthora diseases on crop growth and development). This study showed that the soil bulk density and specific gravity decreased by 6.57%, 1.58%, and 3.65%, 1.86% in T1 and T2 compared to CK. Soil total porosity, capillary porosity, non-capillary porosity, aggregate (>0.25 mm) and water-holding capacity increased by 5.85%, 5.00%, 7.61%, 26.64%, 20.52% and 2.93%, 1.29%, 6.33%, 7.73%, 14.71% in T1 and T2 compared to CK. The soil enzyme (urease, cellulase, alkaline phosphatase, and catalase) activity and soil chemical property increased with the straw return. Compared with CK, T1 significantly increased soil bacterial diversity, while T2 decreased soil bacterial community diversity. Bacterial of Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflex were the dominant phylum. T1 increased the relative abundance of nutrient and beneficial bacteria and decreased the relative abundance of oligotrophic and pathogenic bacteria. In addition, under the normal growth and Phytophthora capsici infected environment, plant height, stem thick, fresh weight and dry weight increased by 22.93%, 11.81%, 61.88% and 23.22% 49.72%, 23.29%, 118.70%, 65.22% in T1 compared to CK. In conclusion, combined application of straw and MCBS not only could significantly improve soil physicochemical properties, stimulate soil enzyme activity but alter soil bacterial community structure diversity and enhance soil pepper Phytophthora disease resistance ability. It helped to promote the sustainable development of Chinese agriculture.