Bacterial diversity as affected by application of manure in red soils of subtropical China

A plot experiment was conducted to understand the response of the soil bacterial community to manure application rates and the relationship between the composition of bacterial community and soil chemical properties. The experiment involved gradients of manure combined with chemical fertilizer in red soils from granite, red sandstone and red clay between 2013 and 2015. The soil bacterial community composition was significantly affected by different manure rates. The relative abundances of Burkholderiaceae, Micrococcaceae and Streptomycetaceae were higher at low manure rates (1.75 to 3.5 t·ha^?1·yr.^?1), whereas the relative abundance of Xanthomonadaceae was higher at high manure rates (7 to 28 t·ha^?1·yr.^?1). Manure application increased the bacterial abundance but decreased the diversity when its rates were higher than 7, 14 and 14 t·ha^?1·yr.^?1 in soils from granite, red sandstone and red clay, respectively. Redundancy analysis revealed that soils from different parent materials had different bacterial communities with soil pH and available phosphorus (AP) being determinant factors. The peanut yields exhibited significantly positive correlations with the bacterial diversity in soil, implying the importance of bacterial diversity for soil productivity. Soil AP was correlated with bacterial diversity by parabolic equations and probably AP may be an indicator of declining bacterial diversity at high manure rates. The critical value were 39.71, 65.75 and 90.16 mg·kg^?1 in soils from granite, red sandstone and red clay, respectively. This study suggests the importance of maintaining soil bacterial diversity under moderate and balanced applications of manure.