Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/18/2014
Publication Date: 11/1/2014
Citation: Gollany, H.T., Polumsky, R.W. 2014. Measured and CQESTR simulated soil organic carbon changes of dryland agroecosystem under climate change scenarios. Meeting Abstract. 54-10. ASA CSSA SSSA 2014 International Annual Meetings. Nov. 2-5, 2014. Long Beach, CA.
Technical Abstract: The potential effects of global climate change (CC) on C cycling and soil organic carbon (SOC) storage/loss in agroecosystems can be assessed by process-based models such as CQESTR. The CQESTR model was used to simulate the effect of tillage and N fertilization on SOC storage/loss in three long-term experiments under dryland wheat-fallow rotation. Using a 30 year simulation approach, the effects of biomass increases/decreases, intensifying cropping and two decades of potential CC scenarios on SOC stock under 0 and 135 kg N/ha (0N and 135N) in no-till (NT) and conventional tillage (CT) management were examined. These SOC stocks were also compared with those of a grass pasture (GP). Predicted SOC stock in the topsoil of the GP increased by 22% with a 30% increase in biomass under current climate compared to CC scenario. The topsoil was more affected by CC than the subsoil. A loss of SOC was predicted at 0-30 and 30-60 cm depths for the CT-0N in all scenarios. The same was true for the CT-135N and NT-0N, except SOC gains of 0.26 and 1.37 Mg/ha were predicted, respectively, for continuous winter wheat under CC scenarios. The NT-135N was the only treatment with SOC gains ranging from 1.35 Mg/ha, in wheat-fallow system with 30% biomass reduction, to 8.61 Mg/ha for continuous winter wheat. Relative to the GP, the C sink capacities of the NT-135N, NT-0N, CT-135N, and CT-0N were 12.69, 14.54, 13.46 and 18.57 Mg/ha, respectively. Crop intensification under NT is a viable management system which could sequester up to 1.05 Mg CO2/ha/yr and improve SOC stock under dryland cropping systems while reducing CO2 in the atmosphere [GRACEnet Publication].