Application of radish (Raphanus sativus L.) optimizing soil fungal communities to increase peanut yield in Ultisol

Long-term continuous peanut monoculture has triggered soil degradation, enriching soil-borne diseases and restricting crop productivity in dryland of Ultisol of southern China. Application of green manure has been regarded as a promising practice to improve soil ecological functions. However, there is little information to explore the appropriated green manure type and evaluate its effect on soil fertility, microbial community and crop yield in dryland of Ultisol. This study comprehensively accessed the effects of three types of green manures (i.e., hairy vetch, ryegrass and radish) on agricultural ecosystem in view of soil fertility and peanut yield by conventional experimental method, and fungal community structure by high-throughput sequencing technology. Application of green manure sustained high nutrient level. The radish treatment decreased soil bulk density and significantly increased peanut yield (26.1%) and straw biomass (17.3%). Application of green manure significantly increased fungal abundance, with the highest abundance found in the radish treatment. The peanut yield was significantly positively correlated with fungal abundance. The treatments of hairy vetch and radish decreased soil fungal evenness and niche breadth, suggesting that certain taxa might be enriched. Consistent with result above, the diversity and relative abundance of plant saprotroph increased in treatments of hairy vetch and radish. Plant saprotroph decomposed soil organic matters to release nutrients for plant growth. The radish treatment had the highest relative abundance of plant saprotroph. In addition, application of radish significantly decreased diversity and relative abundance of plant pathogen. Overall, the peanut-radish rotation might be an appropriated agricultural practice by maintaining soil fertility, optimizing fungal community and improving crop yield in dryland of Ultisol. These findings might provide a theoretical basis for sustainable agriculture development in Ultisol regions.