<UnorderedList Mark="Bullet"> <ItemContent> Bio-organic and slow-release N improved soil C, CEC, and microbial biomass. </ItemContent> <ItemContent> Ammonium and nitrate fertilisers induced P limitation via reduced phosphatase. </ItemContent> <ItemContent> Balanced enzyme ratios reflected optimal microbial nutrient acquisition. </ItemContent> <ItemContent> Fertiliser type shaped whether enzyme–nutrient linkages were coupled or decoupled. </ItemContent> <ItemContent> Nitrogen form determines nutrient retention pathways in tropical soils. </ItemContent> </UnorderedList>Nitrogen (N) fertiliser form is a key regulator of soil microbial processes, yet its role in shaping soil extracellular enzyme and as a stoichiometric indicator remains unclear. We conducted a two-year field experiment (2023–2024) in a tropical perennial durian orchard in Hainan, China, to examine how contrasting N forms influence soil biochemical properties and microbial nutrient acquisition strategies. Six fertilisation regimes were tested, namely control (CK), urea (URT), ammonium sulfate (AMT), calcium nitrate (NT), slow-release N (SRT) and bio-organic fertiliser (BFT). The bio-organic and slow-release N treatments significantly supplemented organic carbon in soils (50%–113%), cation exchange capacity (26%–134%), and microbial biomass C and N (22%–206%), and maintained a relatively constant β-glucosidase (β-G): urease: alkaline phosphatase (ALP) ratio (coordinated nutrient acquisition) by the microbes. Synthetic N fertilisers particularly the nitrate-based and ammonium-based ones, in contrast, altered the stoichiometry of enzymes and deactivated enzyme phosphatase and reinforced phosphorus inhibition, which was followed by a successively growing decline in soil carbon retention. The enzyme-substrate relations (e.g., β-G-SOC, r = 0.76; p < 0.01) were improved under BFT and SRT, but not synthetic N inputs. Multivariate findings indicated that there was segregation in the first year of treatment and partial convergence in the second year, which is a sign in microbial acclimation to the continuous nutrient feeds. Combined, these findings show that N form modulates the patterns of microbial allocation and nutrient fixation systems in tropical soils, and that ecoenzymatic stoichiometry provides a sensitive biochemical quantification of fertilisation responses of soil functional processes.

Nitrogen-driven shifts in soil extracellular enzyme systems and stoichiometric indicators in a tropical ecosystem

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发表日期：

2026年6月20日

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Odhiambo O. Nicholas,
Zhangbing Chen,
Qilin Zhu,
Xunzhun Li,
Chaoqi Liu,
Hua Zhao,
Nathan Okoth Oduor,
Tracy Opande,
Jawad Ullah,
Qiqian Lu,
Xiaoqian Dan,
Jinbo Zhang,
Ahmed S. Elrys,
Xiangdong Zhang,
Lei Meng

摘要

Bio-organic and slow-release N improved soil C, CEC, and microbial biomass.

Ammonium and nitrate fertilisers induced P limitation via reduced phosphatase.

Balanced enzyme ratios reflected optimal microbial nutrient acquisition.

Fertiliser type shaped whether enzyme–nutrient linkages were coupled or decoupled.

Nitrogen form determines nutrient retention pathways in tropical soils.

Nitrogen (N) fertiliser form is a key regulator of soil microbial processes, yet its role in shaping soil extracellular enzyme and as a stoichiometric indicator remains unclear. We conducted a two-year field experiment (2023–2024) in a tropical perennial durian orchard in Hainan, China, to examine how contrasting N forms influence soil biochemical properties and microbial nutrient acquisition strategies. Six fertilisation regimes were tested, namely control (CK), urea (URT), ammonium sulfate (AMT), calcium nitrate (NT), slow-release N (SRT) and bio-organic fertiliser (BFT). The bio-organic and slow-release N treatments significantly supplemented organic carbon in soils (50%–113%), cation exchange capacity (26%–134%), and microbial biomass C and N (22%–206%), and maintained a relatively constant β-glucosidase (β-G): urease: alkaline phosphatase (ALP) ratio (coordinated nutrient acquisition) by the microbes. Synthetic N fertilisers particularly the nitrate-based and ammonium-based ones, in contrast, altered the stoichiometry of enzymes and deactivated enzyme phosphatase and reinforced phosphorus inhibition, which was followed by a successively growing decline in soil carbon retention. The enzyme-substrate relations (e.g., β-G-SOC, r = 0.76; p < 0.01) were improved under BFT and SRT, but not synthetic N inputs. Multivariate findings indicated that there was segregation in the first year of treatment and partial convergence in the second year, which is a sign in microbial acclimation to the continuous nutrient feeds. Combined, these findings show that N form modulates the patterns of microbial allocation and nutrient fixation systems in tropical soils, and that ecoenzymatic stoichiometry provides a sensitive biochemical quantification of fertilisation responses of soil functional processes.