A Scenario Analysis of Conservation Tillage Effects onSoil Organic Carbon Dynamics for Dryland FarmingSystems of Northern China

摘要

Using the Century model to simulate SOC dynamics linked with measurement data fromthe 10y field experiments concerning residue/manure and fertilizer application for dryland cornproduction systems of Northern China resulted in close agreements between simulations and actualmeasurements. The model simulated more accurately over longer time periods when appropriateapplications of stover, manure and inorganic fertilizer were combined. Simulations of extreme C/Nratios of added organic materials (with extremely high C/N organic materials but low N input, or withhigh inorganic N but low organic C input) tended to underestimate the measured effects. The errorof the model ranged from -2.2% to 4.3% of the maximum values observed from each of thetreatments during the period 1995～2002. Scenarios of A) changed tillage methods fromconventional to conservation tillage practices, and B) changed residue practices from 75% to 0%residue removal, especially when combined with inorganic fertilizer N application, showed potentialof maintaining and enhancing SOC in the long run. The Century model simulation showed a goodrelationship between annual C inputs to soil and the rate of C sequestration in the top 20 cm layer,calculated from the simulations of the 10yr field experiments with different amounts ofresidue/manure and fertilizer application. It was estimated that the annual input C is about 1.3 t C(equivalent to 50% residue return) to maintain SOC balance against respiration in this soil. Thefollowing rates of potential C sequestration (in kg C ha-1yr-1) related to management practices werepredicted: 120～270 and 230 with conservation tillage practices and with 100% residue return,respectively; -110～ -140 with convention tillage or 75% residue removal.