Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/12/2010
Publication Date: 7/12/2010
Citation: Prior, S.A., Runion, G.B., Torbert III, H.A., Rogers Jr, H.H. 2010. Effects of atmospheric CO2 and tillage practice on carbon dynamics. In: Soil Properties Dynamics under Different Land Uses, Proceedings of the Uruguayan Society of Soil Science and Uruguayan Branch of the International Soil and Tillage Research Organization, July 12-14, 2010, Colonia del Sacramento, Uruguay. p. 6.
Interpretive Summary: The capability of soil to act as a sink for carbon in CO2-enriched agroecosystems is of special interest in the current climate change policy debate. A 10 year study examine the effects of elevated CO2 in two cropping systems (conventional tillage and no-till). Both systems included a grain sorghum and soybean rotation. The no-till system also included crimson clover, sunn hemp and wheat as winter cover crops. Biomass carbon was increased by high CO2, especially in the no-tillage system. Carbon loss by soil respiration was higher with no-till (particularly under high CO2), but greater residue carbon inputs still led to more soil carbon storage. Findings suggest that adoption of no-till practices may become more important as atmospheric CO2 continues to rise if agriculture is to be viewed as a potential sink for carbon.
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.