No‐Tillage Combined With Fertiliser Optimization Maintains Soil Stoichiometry Balance and Enhances the Soil Carbon Pool

ABSTRACT Tillage and fertilisation strongly influence nutrient inputs and cycling in agricultural ecosystems. The interrelationships among these nutrients can be effectively described using stoichiometric principles. However, the application of stoichiometric principles to understanding agricultural soil carbon (C) pool dynamics remains underexplored. In this study, we investigated the effects of tillage and fertiliser rate on soil stoichiometry and the C pool through a three‐year field experiment in the North China Plain. Treatments included combinations of no‐tillage (NT) and rotary tillage (RT) with 40% (L), 80% (M), and 100% (H) of conventional fertiliser rate. Results showed that soil stoichiometry generally decreased with increasing soil depth. In 2021, no significant differences were observed among treatments in soil stoichiometry and organic carbon (SOC). However, in 2022, tillage significantly ( p < 0.05) impacted the soil C:N ratio, C:P ratio, dissolved organic carbon (DOC), permanganate oxidizable organic carbon (POXC), SOC, SOC stock, and the carbon pool index (CPI) in 0–10 cm soil depth, with NT outperforming RT by 12.3%, 10.4%, 43.1%, 23.0%, 11.4%, 11.8%, and 11.6%. Fertiliser rate mainly influenced DOC and POXC. Among treatments, the NTM had significantly ( p < 0.05) higher DOC, particulate organic carbon (POC), POXC, SOC, SOC stock, and CPI ranging from 48.7%–83.7%, 19.6%–35.9%, 31.9%–63.3%, 13.9%–23.8%, 18.8%–20.2%, and 19.9%–23.1%, respectively, in 0–10 cm soil depth. Redundancy analyses showed that soil stoichiometry is a key indicator explaining variation in the soil C pool. Partial least squares path modelling further revealed that NTM coordinates the impacts of multiple soil processes and mediates the balance between C and nutrients through stoichiometry, thereby enhancing soil C pool. In conclusion, this study reveals the central role of soil stoichiometry in regulating agricultural soil C pool and highlights the synergistic benefits of combining NTM. These practices support soil health, promote sustainable agricultural development, and contribute to climate change mitigation.