Residue decomposition and priming of soil organic carbon following different NPK fertilizer histories

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AbstractThe effect of mineral fertilizer practices on increasing crop yield has been well studied, but few studies have examined the influence of various long‐term subtractive fertilization designs on the decomposition of crop residues or the influence on soil organic carbon (SOC) levels. To assess the combined effects of the long‐term (27‐yr) subtractive fertilizer inputs on SOC mineralization rates, we studied the change in added 13C‐labeled corn (Zea mays L.) stem and leaf residue decomposition and the magnitude of priming effect (PE) on SOC in a 56‐d lab incubation. The long‐term history of nitrogen (N), phosphorus (P), and potassium (K) combinations showed that coupling N and P fertilization had a strong effect on SOC content which increased by 6% relative to the unfertilized treatment. Soil organic C mineralization rates with no residue added were highest in soils that received N, P, and K. Cumulative CO2 production in soils amended with residue was significantly affected by residue type and was 9–19% higher for leaves than stems across treatments with varied fertilization histories. After a 56‐d incubation 14–16% of leaf C and 18–19% of stem C was mineralized. The cumulative PE was significantly higher in the unfertilized soil with leaf addition but was not affected by residue type in other treatments. Our data showed that crop residue decomposition and SOC is affected by historical N, P, and K fertilization, with long‐term complete NPK application resulting in greater SOC content and slower SOC mineralization rates with corn leaf addition.