Optimizing nutrient stoichiometry for enhanced carbon sequestration in agricultural soils

Area of Science:

• Soil Science
• Biogeochemistry
• Environmental Science

Background:

• Plant and microbial growth depend on essential nutrients: nitrogen (N), phosphorus (P), and sulfur (S).
• Soil organic carbon (SOC) stabilization is influenced by nutrient availability and the elemental composition of soil organic matter (SOM).
• Humus, the most stable SOM fraction, exhibits a characteristic C:N:P:S ratio of 10,000:833:200:143.

Purpose of the Study:

• To investigate the impact of varying C:N:P:S ratios on SOC stabilization.
• To assess how amending soils with crop residues and inorganic nutrients affects carbon dynamics.
• To determine optimal nutrient ratios for enhancing carbon sequestration in soils.

Main Methods:

• A six-month laboratory incubation experiment was performed on benchmark soil series.
• Soils were amended with wheat straw (WS) and maize straw (MS), with and without N, P, and S addition.
• Target C:N:P:S ratios were set at 15% and 30% of humus stoichiometry.

Main Results:

• Treatments with 30% humus-based ratios (MS30% and WS30%) reduced CO₂ efflux by 39% and 33%, respectively, compared to unamended controls.
• 15% humus-based ratio treatments (MS15% and WS15%) decreased CO₂ emissions by 14% compared to straw-only applications.
• Nutrient supplementation to achieve a 30% humus-based ratio increased SOC stabilization by 11-25% over straw-only treatments.

Conclusions:

• Aligning organic and inorganic inputs to a 30% humus-based C:N:P:S ratio significantly enhances SOC stabilization.
• Balanced nutrient management is crucial for maximizing carbon sequestration potential in soils.
• This approach contributes to improving overall soil health and mitigating climate change through carbon storage.