The main controlling factors and coupling relationship of functional gene abundance in carbon and nitrogen cycling in dryland red soil with biochar and biogas slurry co-application
Carbon-nitrogen biogeochemical cycling characteristics under the combined application of biochar and biogas slurry is critical for analyzing the agricultural soil fertility enhancement.The subject of this study was typical upland red soil.Over a four-year field trial,biochar was applied at rates of 0% and 2% (C0 and C1),in combination with replacing 0% and 100% of liquid slurry(B0 and B1)to investigate changes in soil physicochemical properties,abundance of carbon and nitrogen cycling functional genes,and their coupling relationships.The combined application of biochar and biogas slurry(C1B1 treatment)increased soil pH by 1.92,reduced bulk density by 19.2%,and increased total nitrogen content by 268.6%,when compared with the control(CK)treatment.Multivariate nonlinear regression models showed that ammonium nitrogen(NH+4-N),nitrate nitrogen(NO-3-N),and water-soluble organic carbon(WSOC)were the primary factors influencing the abundance of carbon and nitrogen cycling functional genes.Furthermore,significant positive correlations were found between denitrification functional genes(nar G,nir K,nir S,and nos Z)and carbon degradation genes(chi A,pug,naglu,and gcd),carbon fixation genes(rbc L,frd A,pcc A,and mct),as well as methane metabolism genes(mxa F and pmo A).The research findings demonstrate that the combined application of biochar and biogas slurry significantly improves soil quality,and alters the abundance of functional genes in the carbon and nitrogen cycle by affecting the content of soil carbon and nitrogen forms,ultimately regulating the carbon and nitrogen cycling process of the soil.
biocharbiogas slurryupland red soilcarbon-nitrogen cyclefunctional genes
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