Abstract
The biogeochemical interactions between soil nutrients and microbial enzymes in agroecosystems remain poorly understood. The objective of this study was to determine effects of long-term (26 years) application of chemical fertilizers (NPK) or adding manure (M) on the elemental and the enzymatic functional stoichiometric characters in a brown soil. The concentrations of soil elements, i.e. carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) and the activities of soil hydrolases including α (β)‑galactosidase (α-GAL and β-GAL), α (β)‑glucosidase(α-GLU and β-GLU), urease, protease (PR), phosphomonoesterase (PM), Phosphodiesterase (PD) and arylsulfatase (AS) were investigated.Results showed that the NPK additions alone led to a decrease in soil pH and increased the acidification of the soils, while M additions could buffer the acidification. With doubling application rate of M, the concentrations of soil C, N, P and S, and soil enzymes activities increased significantly, but P concentrations increased stronger (doubled) than C and N contents (increased by 30%), leading to shifts in element stoichiometry in response to fertilizer and manure applications. The manure additions led to a relatively constant C:N ratio, a low C:P ratio and a high C:S ratio but lower functional ratios of ln (β-GLU + α-GLU + α-GAL + β-GAL): ln(urease + PR); ln(GLU + GAL): (PM + PD); and ln(GLU + GAL):ln(AS), which implied high availability of P and low availability of S. The comparison of element and enzyme stoichiometry indicated that N and S were limited in the manure plots, and C and P were limited in the NPK and No-NPK fertilizer treatment (WF) plots. The increase in enzyme activities in manure plots was caused primarily by the accumulation of soil nutrients with M treatment and not by a buffering effect on the pH.
Published Version
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