Stratified Nitrogen Application Enhances Subsoil Carbon Sequestration via Enzyme-Mediated Pathways in Straw-Incorporated Croplands of North China Plain

Bin Wang, Yanqun Wang, Jingyu Li, Rui Hou, Yulong Liu, Xin Fu (), Jie Men, Yingchun Li and Zhengping Peng ()
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Bin Wang: State Key Laboratory of North China Crop Improvement and Regulation, Hebei Agricultural University, Baoding 071000, China
Yanqun Wang: State Key Laboratory of North China Crop Improvement and Regulation, Hebei Agricultural University, Baoding 071000, China
Jingyu Li: Key Laboratory of Farmland Ecological Environment of Hebei Province, Hebei Agricultural University, Baoding 071000, China
Rui Hou: Key Laboratory of Farmland Ecological Environment of Hebei Province, Hebei Agricultural University, Baoding 071000, China
Yulong Liu: Key Laboratory of Farmland Ecological Environment of Hebei Province, Hebei Agricultural University, Baoding 071000, China
Xin Fu: Key Laboratory of Farmland Ecological Environment of Hebei Province, Hebei Agricultural University, Baoding 071000, China
Jie Men: Key Laboratory of Farmland Ecological Environment of Hebei Province, Hebei Agricultural University, Baoding 071000, China
Yingchun Li: Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Zhengping Peng: State Key Laboratory of North China Crop Improvement and Regulation, Hebei Agricultural University, Baoding 071000, China

Agriculture, 2025, vol. 15, issue 19, 1-23

Abstract: Nitrogen (N) fertilization critically regulates the storage and availability of soil carbon (C) and N pools. However, the internal mechanism through which stratified N application affects soil organic carbon (SOC) sequestration and soil quality index (SQI) remains unclear. To investigate the effects of stratified N application on C sequestration and SQI in both topsoil and subsoil, this study established six treatments (N 0:0 , N 1:0 , N 4:1 , N 3:2 , N 2:3 , N 1:4 ) and analyzed soil biochemical indicators. The results showed that compared to N 1:0 , stratified N fertilization did not significantly improve soil C and N content in the 0–20 cm layer. In contrast, the N 2:3 and N 1:4 treatments even led to a significant reduction in soil C and N pools in the topsoil. In the 20–40 cm, compared to N 1:0 , stratified N fertilization increased SOC, TN, labile C fractions, N fractions (particulate organic N and microbial biomass N), enzyme activity and C pool management index (CPMI), increasing by 0.52–7.94%, 2.05–8.42%, 4.77–42.59%, 14.46–56.01%, 6.34–45.82%, and 31.26–51.93%, respectively. In 0–20 cm, compared to N 0:0 , N application increased SQI by 24.84–45.77%, and N 2:3 and N 1:4 treatments were lower SQI than N 1:0 . Furthermore, N 2:3 , N 3:2 , and N 1:4 treatments in 20–40 cm were higher than other treatments. N fertilizer application drives the synergistic changes in C and N fractions by regulating enzyme activity and stoichiometric ratio, thus affecting CPMI and SQI. Thus, the 3:2 stratified N fertilization (0–20 cm:20–40 cm) method achieves synergistic dual-layer enhancement-maintaining surface C and N pools while boosting subsoil C sequestration and quality-through enzyme-mediated precision regulation of C/N stoichiometry. The study provides a scientific foundation for integrated C emission reduction and cropland quality enhancement in the North China.

Keywords: stratified fertilization; C and N fractions; enzyme activity; soil quality index; north China plain (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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