Novel environmental factors affecting microbial responses and physicochemical properties by sequentially applied biochar in black soil.

Biochar was increasingly used in agriculture soil amendment and has received widespread attention due to its potential to improve soil micro-ecological environment and crop growth. The raw material of the biochar used in this study is peanut shell, which is mixed with other organics and minerals to become a mineral-enhanced biochar under heating conditions (220 °C). When the third season crop is finished, we evaluated black soil physicochemical properties, microbial communities, and crop growth in long-term agricultural trials. Four treatments were set up: no amendment (control CK), nitrogen fertilizer only (70 kg ha-1 N), enhanced biochar only (5 t ha-1 B), and nitrogen fertilizer (70 kg ha-1) + enhanced biochar (5 t ha-1) (NB). The enhanced biochar promotes crop growth and increased the richness of the bacterial community, while reducing the richness of the fungal community. Nitrogen fertilizer + enhanced biochar increased soil microbial biomass carbon, nitrate nitrogen, and ammonium nitrogen by 43.75, 7.25, and 19.28%. In addition, we found changes in bacterial community were closely related to soil organic carbon, while changes in fungal community structure were closely related to soil carbon to nitrogen ratio. And the soil organic carbon and soil carbon to nitrogen ratio of biochar treatment were increased by 5.64 and 6.25% compared with fertilizer treatment, respectively. We concluded that enhanced biochar improved the soil more effectively and made the soil more conducive to crop growth. Regulating the microbial community by improving the physicochemical properties of soil was an important way to improve the stability and condition of the soil system with biochar. An enhanced biochar was of great significance for circular development of agriculture and soil improvement in Northeast China.