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 indica te that roots and rhizodeposition are important sources of carbon for the s ynthesis of soil organic carbon. Our objective was to verify the capability of the simulation model NCSWAP to reproduce the general conclusions from t he experimental literature, and to gain some insight about the processes th at control the incorporation of corn belowground production into the soil o rganic matter. The model was calibrated against the experimental data gathe red 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 pro duction, and the total soil organic matter, soil delta value, and the soil organic matter derived from corn in the 0-15 and 15-30 cm depth. The simula tion gave a root-plus-rhizodeposition 1.8 times larger than stalks plus lea ves. 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 s ensitivity of below-ground photosynthate incorporation into the soil organi c 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 mon photosyn thates were translocated to rhizodeposition than to roots. (C) 2001 Elsevie r Science Ltd. All rights reserved.