Soil pH Amelioration Fosters Persistent Carbon Sinks Through Mineral Stabilization and Aggregate Protection

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Soil organic carbon (SOC) stability is vital for agricultural carbon credits, but its prediction and verification are challenging.
• Isolating the impact of soil pH amelioration from other factors like organic matter inputs is a key methodological hurdle.

Purpose of the Study:

• To quantitatively disentangle the effects of soil pH amelioration on various soil organic carbon components.
• To investigate how pH influences SOC stability across different soil fractions and aggregate structures.
• To provide a mechanistic understanding for optimizing carbon sequestration through pH management.

Main Methods:

• Bivariate linear mixed-effects modeling applied to a global synthesis of 180 field trials.
• Analysis of SOC components across a stability continuum, including bulk soils and aggregate fractions.
• Structural equation modeling to elucidate hierarchical drivers of pH-induced carbon stabilization.

Main Results:

• pH amelioration increased bulk SOC stocks by 18%-20%.
• Mineral-associated organic carbon and microbial necromass carbon increased by 11%-15% and 12%-19%, respectively.
• Enhanced aggregate stability and carbon enrichment in microaggregates (up to 44% in alkaline soils) were observed, driven by microbial biomass shifts.

Conclusions:

• pH amelioration is a fundamental process for creating persistent carbon sinks by directing carbon into mineral-stabilized and physically protected pools.
• Precision pH management is an essential ecological engineering strategy for enhancing soil carbon sequestration.
• This research provides a mechanistic basis for shifting carbon credit verification from stock-based accounting to stability-centric approaches.