Responses of soil bacterial community and enzyme activity to organic matter components under long-term fertilization on the Loess Plateau of China

Soil bacterial community structure, enzyme activities and their relationships to soil carbon and nitrogen in response to long-term fertilization remain poorly understood. Therefore, the objective of this study was to evaluate soil carbon and nitrogen fractions, enzyme activity, and bacterial community structure at 0-15, 15-30, and 30-60 cm depths after 34-yr of continuous application of manure and inorganic fertilizers. The study had a randomized complete block design with six treatments and three replications. Treatments were inorganic nitrogen fertilizer only (N), nitrogen plus phosphrous fertilizers (NP), manure (M), nitrogen plus manure (NM), nitrogen plus phosphorus plus manure (NPM), and unfertilized control (CK) in a winter wheat (Triticum aestivum L.) monoculture system. Most soil carbon and nitrogen fractions at 0-15 and 15-30 cm were greater with M, NM, and NPM, and winter wheat yield was greater with NPM than other treatments. The NPM increased 13-glucosidase, 13-xylosidase, and 13-N-acetylglucosidase compared to other treatments at all depths. Soil bacterial Shannon index was similar among treatments at 0-15 and 15-30 cm and lower in N and NP than other treatments at 30-60 cm. Compared to CK, inorganic and manure fertilization increased relative abundances of Gemmatimonadetes and Bacteroidetes but decreased those of Nitrospirae, Planctomycetes, and Latescibacteria. Increases in soil enzyme activities and bacterial communities after long-term application of inorganic N and P fertilizers and manure was related to increased substrate availability. Overall, a combination of chemical fertilizers and manure can enhance soil health and quality through increased soil organic matter component, enzyme activity, and bacterial abundance.

Automated summary

Long-term application of inorganic nitrogen and phosphorus fertilizers and manure can increase soil carbon and nitrogen fractions, enzyme activities, and bacterial community structure, with the NPM treatment showing the best performance in all aspects.