Response of bacterial community structure and diversity to different fertilization regimes in the rhizosphere soil of Camellia oleifera

Camellia oleifera is a high quality woody oilseed crop that produces a low yield in the central subtropics of China. Although fertilization can efficiently increase C. oleifera yield in these areas, the influences of fertilization continuously on soil microbiota and soil fertility remain poorly understood. The purpose of this study was to determine the influences of the type and amount of fertilizer on the soil properties of C. oleifera. Here, we compared the effects of organic fertilizer, organic–inorganic compost, no fertilizer control, and low (F1), medium (F2), and high (F3) amounts of continuously applied organic–inorganic compost at the sapling stage All chemical indicators and copiotropic bacteria measured were significantly lower in organic fertilizer and without fertilizer. Successive fertilization over two years with organic-inorganic compost significantly altered the relative abundance of the dominant bacterial groups at the phylum levels. the abundance of these phyla was the same in F2 and F3 treatments which was higher than their abundance in the other treatments. The relative abundance of kopiotrophic bacteria, especially proteobacteria and gemmatimonadetes, increased significantly and similarly with F2 and F3 treatments. With successive fertilizations, the levels of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) were the vital factors affecting bacterial communities, which was confirmed by structural equation models, redundant analyzes and random forest models. These results suggest that the continuous application of moderate amounts of organic-inorganic compost is the main driver for the improvement of soil bacterial communities, and this was mainly achieved by altering the levels of OM, TN and TP, thus affecting the copiotropic bacterial abundance. This study provides a scientific basis for optimal fertilization of C. oleifera forest.