Simulating the effect of potassium fertilization on carbon sequestration in soil

The impact of horticultural management on carbon sequestration in soils has been limited so far to tillage and nitrogen fertilization. Our objective was to evaluate by mathematical modeling the effect of potassium fertilization on CO₂ binding in cropland soils. The developed model integrates three subunits: (1) A published simulator of crop dry-matter (DM) production in response to N, P, K fertilization, but not DM partitioning; (2) a published soil-crop-atmosphere model predicting crop yield and DM partitioning as a function of N but not K fertilization; (3) an original model computing the organic-inorganic carbon transformations, inorganic-carbon reactions and transport in soil, CO₂ diffusion, and soil carbon sequestration. The model described the K-fertilization effect on C binding in soil as a function of the soil pH, the Ca²⁺ concentration in the soil solution, hydraulic properties, air temperature, and crop DM production, and partitioning characteristics. In scenarios of corn (Zea mays L.) growth in clayey soil and wheat (Triticum aestivum L.) in loam soil, the computed K-induced CO₂ sequestration amounted to ≈14.5 and 24kg CO₂ (kg K)^-1, respectively (0 vs. 100kg ha^-1 K application). The soil CO₂ sequestration declined by 8% when corn grew in sandy instead of clayey soil and by 20% when the temperature was 10°C higher than the temperature prevailing in mild semiarid zones. All predicted CO₂-sequestration results were approximately 30-fold higher than the 0.6kg CO₂ emitted perkg of K manufactured in industry.