ABSTRACT
The chapter seeks to review changes in soil organic carbon (SOC) in Canadian agroecosystems, with particular emphasis on the effects of various management options. It aims to determine the trajectory of soil C dynamics, describe some of the rate-determining mechanisms, and estimate the potential of various agroecosystems for removing atmospheric carbon dioxide (CO2). The emission of CO2 from external energy expenditure also merits inclusion in the overall C cycle of a given agroecosystem. Projected changes whose influence on future SOC dynamics also deserve attention include changes to climate, atmospheric CO2 concentration, ultraviolet-B intensity, and N deposition patterns. Historically, Canadian agricultural soils have been a significant source of atmospheric CO2. Approximately 25% of the SOC originally present in the surface layer was lost to the atmosphere upon conversion to arable agriculture. Most agriculture soils in Canada have been cultivated for a sufficient duration that any lingering effects of the initial cultivation are probably overshadowed by the impact of management options.
