Techniques for measuring soil organic C (SOC) turnover in production fields are needed. The objectives of this study were to propose and test nonisotopic and 13 C stable isotopic techniques for assessing SOC turnover. Based on SOC equilibrium and mass balance relationships, an equation was derived: NHC/SOC initial=[1/(SOC× k NHC)](dSOC/dt)+ k SOC/k NHC, where dSOC/dt is the annual change in SOC, NHC is nonharvested C returned to soil, k SOC is the annual mineralization rate of SOC, and k NHC is the annual mineralization rate of NHC. This equation was used to calculate maintenance rates. An isotopic approach based on simultaneously solving the equations was developed to determine C budgets:(i) SOC retained=[SOC final (Δ soil final− Δ PCR)/(Δ SOCretained− Δ PCR)];(ii) Δ SOC retained= Δ soc initial−[ε ln (SOC retained/SOC initial)],(iii) Δ PCR= Δ NHC−[ε ln (PCR/NHC)]; and (iv) SOC final
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American Society of Agronomy
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Clay, D. E.; Carlson, C. G.; Clay, S. A.; Reese, C.; Liu, Z.; Chang, J.; and Ellsbury, M. M., "Theoretical Derivation of Stable and Nonisotopic Approaches for Assessing Soil Organic Carbon Turnover" (2006). Agronomy, Horticulture and Plant Science Faculty Publications. 164.