ARS | Publication request: EFFECTS OF CO2 AND DROUGHT ON N2 FIXATOIN IN FIELD-GROWN SOYBEAN PLANTS.

Submitted to: Ecology Society of America Abstracts
Publication Type: Abstract
Publication Acceptance Date: April 15, 2005
Publication Date: August 1, 2005
Publisher's URL: http://abstracts.co.allenpress.com/pweb/esa2005/document/?1D=50532
Citation: Van Bloem, S.J., Leakey, A., Ort, D.R., Gonzalez-Meler, M., Thomas, R.B. Effects of CO2 and drought on N2 fixation in field-grown soybean plants [abstract]. Ecology Society of America Abstracts. Available: http://abstracts.co.allenpress.com/pweb/esa2005/document/?1D=50532.

Technical Abstract: The effects of elevated concentrations of atmospheric CO2 on plant productivity are of great concern in agricultural systems. In soybean, increased concentrations of CO2 have been shown to increase photosynthesis and carbon allocation to developing organs, including roots. Increased carbon transport may increase crop production by stimulating symbiotic N2 fixation in legumes. Conversely, drought has been shown to reduce N2 fixation in soy bean. Climate models combining elevated CO2 with regional weather conditions suggest that some soy bean grown areas will experience increased drought along with higher CO2 elevations, thus drought may counteract beneficial aspects of increased CO2. Our study measured nodulation and N2 fixation in soybean (Glycine max) plants in response to a full factorial combination of drought and CO2-at the University of Illinois Free Air CO2 Enrichment (SoyFACE) experiment. CO2 concentrations were elevated to 550 ppm and the drought treatment diverted rainfall from 40% of the plot area. Fixation was determined using natural abundance of 15N and a non-nodulating isoline of soybean as a reference. Whole soybean plants were harvested in early September at peak plant biomass. Plants grown under elevated CO2 had 70% greater nodule mass than control plants, resulting in 130% greater fixed N and a 62% greater ratio of fixed to total N in CO2-grown plants. At elevated CO2, water-stressed plants showed only minor differences in N2 fixation and nodule mass compared to control plants. These results from the first year of this study track results from greenhouse experiments that suggest elevated CO2 will mitigate the deleterious effects of drought on N2 fixation in soy bean. However, field conditions result in high seasonal and interannual variability in weather patterns which will influence the strength of response to drought and the ability of elevated CO2 to mitigate drought effects.