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United States Department of Agriculture

Agricultural Research Service

Title: Elevated Atmospheric Co2 Effect on N Fertilization in Grain Sorghum and Soybean

Authors
item TORBERT, HENRY
item PRIOR, STEPHEN
item Rogers Jr, Hugo
item RUNION, GEORGE

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 26, 2003
Publication Date: April 19, 2004
Citation: Torbert III, H.A., Prior, S.A., Rogers Jr, H.H., Runion, G.B. 2004. Elevated atmospheric co2 effect on n fertilization in grain sorghum and soybean. Field Crops Research. 88(1):47-57.

Interpretive Summary: Increasing levels of CO2 in the atmospheric continues to be concerns regarding potential changes to the global environment. One area in this regard that has not been fully addressed is the effect of elevated atmospheric CO2 on agriculture production inputs, especially N fertilizer. This study was conducted to examine the effects of growing soybean and grain sorghum plants under normal or twice normal CO2 conditions on N fertility. Elevated CO2 increased total biomass production of both grain sorghum and soybean in all three years. With soybean, which can fix N from the air, the total N content was greatly increased with elevated CO2 concentration. With grain sorghum, the total N uptake was not affected by elevated CO2. No impact of elevated CO2 level was observed for fertilizer N in grain sorghum. The results from this study indicated that while elevated CO2 may enhance crop production and change N status in plant tissue, changes to soil N fertilizer application practices may not be needed.

Technical Abstract: Increasing atmospheric CO2 concentration has led to concerns about global changes to the environment. One area of global change that has not been fully addressed is the effect of elevated atmospheric CO2 on agriculture production inputs. Elevated CO2 concentration alterations of plant growth and C:N ratios may modify C and N cycling in soil and N fertility. This study was conducted to examine the effects of legume, soybean [Glycine max (L.) Merr.], and non-legume, grain sorghum [Sorghum bicolor (L.) Moench.] carbon dioxide-enriched agro-ecosystems on N soil fertility in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study was a split-plot design replicated three times with crop species (soybean and grain sorghum) as the main plots and CO2 concentration (ambient and twice ambient) as subplots using open top field chambers. Fertilizer application was made with 15N-depleted NH4NO3 to act as a fertilizer tracer. Elevated CO2 increased total biomass production of both grain sorghum and soybean in all three years. With soybean, while no impact on the plant C:N ratio was observed, the total N content was greatly increased due to increased atmospheric N2 fixation with elevated CO2 concentration. With grain sorghum, the total N uptake was not affected, but the C:N ratio was markedly increased by elevated CO2. No impact of elevated CO2 level was observed for fertilizer N in grain sorghum. The results from this study indicated that while elevated CO2 may enhance crop production and change N status in plant tissue, changes to soil N fertilizer application practices may not be needed.

Last Modified: 9/10/2014
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