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 soilcropatmosphere 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 approximate to 14.5 and 24kg CO2 (kg K)1, respectively (0 vs. 100kg ha1 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 degrees 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.