Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/24/2012
Publication Date: 9/24/2012
Citation: Prior, S.A., Runion, G.B., Torbert III, H.A., Rogers, H.H. 2012. Impact of increasing atmospheric co2 on carbon dynamics under different tillage practices. In: Proceedings of the International Soil Tillage Research Organization Proceedings. CDROM.
Interpretive Summary: The ability of soil to store carbon in CO2-enriched cropping systems is of interest in the ongoing climate change policy debate. A 10 year study looked at how elevated CO2 impacted conventional tillage and no-till cropping systems. Both systems had a grain sorghum and soybean rotation and the no-till system also included crimson clover, sunn hemp and wheat as winter cover crops. Plant carbon was increased by high CO2, especially under no-tillage. Carbon loss by soil respiration was higher with no-till (particularly under high CO2), but greater residue carbon inputs still increased soil carbon storage. Results indicated that no-till farming may become more important in storing more carbon in soil as atmospheric CO2 continues to rise in the future.
Technical Abstract: Increasing atmospheric CO2 concentration may impact production agriculture=s role in sequestering carbon (C). A 10-year study compared the effects of elevated CO2 on two cropping systems (conventional tillage and no-tillage). The experiment was a split-plot design replicated three times with these cropping systems as main plots and two CO2 levels (ambient and twice ambient) as subplots using open top field chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional tillage system consisted of a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation using spring tillage and winter fallow. In the no-tillage system, sorghum and soybean were rotated and three cover crops (also rotated) were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)] using no-tillage practices. The no-tillage system had either cash or cover crops grown throughout the year with no fallow periods (in order of: clover, sorghum, sunn hemp, wheat, and soybean). The effect of these two contrasting management systems on crop biomass C production (yield and non-yield components), soil C efflux and storage were evaluated. Biomass C production (including grain C) was increased by high CO2, especially in the no-tillage system. Although C lost via soil respiration was greater in the no-tillage system (particularly under CO2-enriched conditions), greater residue C inputs still resulted in increased soil C. These findings indicate that adoption of no-tillage management practices will become even more crucial as atmospheric CO2 continues to rise if agriculture is to be viewed as a potential sink for carbon. A better understanding of changes in C dynamics under elevated CO2 is critical for predicting the potential of agricultural systems to store C in soil which can improve soil health and assist in mitigating aspects of climate change.