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Abstract The utilization of agricultural waste organic materials through composting technology has gained significant traction in agricultural production as an effective means of crop nutrient management. However, the differences in the impact of organic amendments prepared by traditional composting and vermicomposting on soil properties still deserve further research. Based on field experiments conducted in greenhouse, compared to chemical fertilizer treatments as control, we utilized traditional compost (OF) and vermicompost (VcF) derived from agricultural organic waste edible mushroom bran and cow manure (2:8). Variations in soil physiochemical properties, activities of soil enzymes related C and P cycling, abundances and diversities of bacterial 16S rRNA and fungal ITS gene at total DNA level were analyzed. Both compost treatments enhanced soil organic carbon, soil total phosphorus, and soil available P content significantly and also increased the activities of soil α‐glucosidase, β‐glucosidase, acid phosphomonoesterase, and alkaline phosphomonoesterase significantly. The above results suggested that soil C and P transformations were stimulated effectively by both organic amendments. OF and VcF increased the fungal ITS absolute abundances significantly while diversity indices of soil bacterial community increased significantly under both treatments. Correlation analysis indicated that bacterial community composition was strongly correlated with several soil property indexes while fungal community composition was only significantly correlated with soil total phosphorous content. In conclusion, similar to traditional compost, vermicompost significantly improved soil nutrient cycling (especially C and P aspects). In terms of soil microbes, bacteria and fungi showed different responding mechanism to vermicompost: bacteria adjust microbial structure, while fungi tend to proliferated. In consideration of the advantages of vermicompost in technology and economic cost, it could be applied in the subsequent agricultural production more frequently.

Abstract Soil nitrogen (N) is a vital source of nutrients for maintaining soil fertility and crop production. However, the effect of biochar application rate on the mechanism of organic N transformation and the contribution of enzyme mineralization is still unclear. Therefore, we conducted two 5‐year field experiments in contrasting soils (Phaeozem and Luvisol) with biochar application rate at 0 t hm−2 (CK, 0), 22.5 t hm−2 (D1, 1%), 67.5 t hm−2 (D2, 3%), and 112.5 t hm−2 (D3, 5%) to investigate the potential effects of biochar application rate on soil organic nitrogen (N) turnover and its linkage to enzymatic mineralization in contrasting soil. The results showed that soil organic carbon (SOC) and microbial biomass nitrogen (MBN) contents, microbial biomass carbon to nitrogen ratio (MBC:MBN) and protease activity are significantly influenced by biochar application rate whereas not by soil type. Ammonium nitrogen (NH4+‐N) and nitrate nitrogen (NO3−‐N) contents, and dehydrogenase activity are significantly changed by soil type whereas not by biochar application rate. Based on the redundancy analysis, we found that organic N fractions are associated with MBN, SOC, and protease in Phaeozem, but related to protease activity in Luvisol. Our findings indicate that organic N turnover is not only related to the bioavailability of N but also requires carbon substrates in Phaeozem, whereas the transformation of organic N in Luvisol is dominated by enzymatic mineralization as the relatively low level of bioavailable N.

Abstract To understand how stover incorporation affects the levels of soil carbon and its biogeochemistry process, we examined soil carbon and amino sugar carbon (AS‐C). Activity of N‐acetylglucosaminidase (NAGase) and the abundance (real‐time quantitative polymerase chain reaction, RT‐qPCR) and communities of the bacterial chitinase‐encoding gene (chiA) were monitored. We implemented a maize cropping system, which included four treatments, i.e., chopped maize stover returned directly (SD), compost produced by maize stover (SC), biochar produced by maize stover (BC), and stover removal (CK). The results showed that BC and SD enhanced soil organic carbon (SOC), microbial biomass carbon:SOC, total AS‐C, glucosamine carbon, galactosamine carbon, NAGase activity, and chiA gene abundance significantly. There were significant positive correlations between the abundance of the soil chiA gene and NAGase activity. Biochar and stover treatments increased the number of total operational taxonomic units (OTUs), unique OTUs, and the chao 1 and ACE richness indices, but decreased the Shannon and Simpson diversity indices. The dominant chiA‐harboring bacterial phyla were Actinobacteria, Proteobacteria, and Bacteroidetes. Some detectable genera in Actinobacteria had high relative abundance, including Streptomyces, Actinoplanes, and Amycolatopsis. PLS‐DA and CCoA revealed that the chiA community in the BC or SD plots was significantly different from that in the CK plots, and differences between BC and SD were not significant. Similar soil properties, diversity, and the abundance of chiA were observed between SC and CK. Greater abundance and diversity of the chiA gene with BC incorporation were associated with higher pH, SOC, and TN concentration. Soil pH was related to the composition and abundances of the chiA‐harboring microbial communities (CCA).