Chapter 16 - CQESTR Simulations of Soil Organic Carbon Dynamics

Abstract

A process-based carbon (C) model, CQESTR (sequester), was used to predict soil organic carbon (SOC) dynamics and examine the effect of agricultural management practices on SOC accretion in three diverse regions of the U.S. The three regions chosen had long-term experiments (LTEs) ranging from 23 to 134 years in duration. The range of management practices included crop residue harvest, burning or residue retention, tillage type, fertilizer or manure addition, fallow and crop intensification, monoculture and complex crop rotation. The CQESTR model captured temporal and spatial changes in SOC. Simulation results indicated cultivation and crop residue removal decreased SOC; however, with appropriate management such as the use of conservation tillage, organic amendments, and/or cropping intensification, SOC losses could be reversed. Using fertilizer alone is insufficient to overcome residue removal effects on SOC. Model validation and future predictions concerning SOC management can only be conducted using a long-term (>25-year) SOC database because stable SOC changes occur very slowly and require several decades to reach equilibrium.