Modeling the incorporation of corn (Zea mays L.) carbon from roots and rhizodeposition into soil organic matter

Experimental data reported in the literature over the last decennium indicate that roots and rhizodeposition are important sources of carbon for the synthesis of soil organic carbon. Our objective was to verify the capability of the simulation model NCSWAP to reproduce the general conclusions from the experimental literature, and to gain some insight about the processes that control the incorporation of corn below-ground production into the soil organic matter. The model was calibrated against the experimental data gathered from a long-term field experiment located near St. Paul, Minnesota. The simulation model updated daily the soil conditions to reproduce over a 13 year period the measured kinetics of seven variables: above-ground corn production, and the total soil organic matter, soil δ value, and the soil organic matter derived from corn in the 0–15 and 15–30 cm depth. The simulation gave a root-plus-rhizodeposition 1.8 times larger than stalks plus leaves. The translocation efficiency of corn-C into soil organic C at the 0–15 cm depth gradually decreased to 0.19 of the below-ground deposition. The sensitivity of below-ground photosynthate incorporation into the soil organic matter was analyzed relative to variations in the parameters that control the formation and decay of roots and rhizodeposition. Roots had a greater effect than rhizodeposition on the soil organic matter, though more photosynthates were translocated to rhizodeposition than to roots.