Submitted to: Journal of Crop Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2001
Publication Date: 10/10/2003
Citation: Prior, S.A., Torbert, H.A., Runion, G.B., and Rogers, H.H. 2003. Implications of elevated CO2-induced changes in agroecosystem productivity. Journal of Crop Production 8 (1/2):217-244. Interpretive Summary: The increasing level of CO2 in the atmosphere has led to concerns regarding potential changes in the global environment, crop production and associated management considerations. Our goal was to determine how elevated CO2 would affect soybean and sorghum cropping systems in a long-term field study. CO2-induced increases in grain production was greater for soybean compared to sorghum, however increases in non-yield residue (both above and belowground) were similar for both crops. Increases in non-yield residue inputs could negatively impact crop stand establishment and implement effectiveness during tillage operations. CO2 enhancement of non-yield biomass production suggests greater delivery of C to soil, more soil surface residue and greater percent ground coverage which could alter soil physical properties, reduce soil erosion, increase soil water and carbon storage, thereby increasing soil productivity. More rooting also implies the possibility of more water and nutrient capture.
Technical Abstract: There is interest in how increasing atmospheric CO2 will affect crop productivity and alter agricultural management. This field study evaluated soybean and sorghum systems managed under conservation tillage practices and two CO2 levels (ambient and 2X ambient) for three yrs. High CO2 increased soybean yield (53 %) more than sorghum (17%); reductions in soybean whole plant water use were also greater. Thus, high CO2 could improve future food security, especially in soybean systems. High CO2 increased aboveground residue (non-yield) by >35% (both crops); such shifts could complement conservation management by increasing soil surface cover, thereby reducing soil erosion. But, more residue could hinder crop stand establishment and implement effectiveness during tillage operations. High CO2 increased belowground dry weight (both crops); increased rooting may alter soil structure which may increase porosity, infiltration rates, and soil water storage. Nitrate leaching was reduced during the growing season (increased N capture) and fallow period (altered decomposition). Enhanced crop growth under high CO2 suggests greater delivery of C to soil, more soil surface residue (and ground cover) which could reduce soil CO2 losses, increase soil C storage, and help ameliorate the rise in CO2. To fully elucidate the relationships between crop productivity, nutrient cycling, and residue decomposition in high CO2 environments, future studies must consider species effects (including genetically modified crops) and other factors such as cover crops, crop rotations, soil series, tillage practices, weed management, and regional climatic differences.