A new method to determine soil organic carbon equilibrium

This work addresses the dynamical behaviour of the Pasture Simulation Model (PaSim), with respect to the equilibrium conditions for the five carbon (C) pools (structural, metabolic, active, slow, and passive) of soil organic matter (SOM) decomposition, which are modelled according to CENTURY. A novel algebraic approach, based on a sequence of matrices and formulated using the Gauss-Jordan (G-J) elimination algorithm (stable and efficient in memory usage), was proposed and compared to a native iterative procedure using soil C data from 13 European grassland sites. The advantage of the algebraic approach over the iterative method is an enhanced accuracy of C allocation to soil pools and a faster convergence (6–20 times). Its value was discussed in the context of SOM research and modelling.