Submitted to: GCTE Focus 3 Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 20, 1999
Publication Date: N/A
Technical Abstract: Increasing atmospheric CO2 concentration has led to concerns about global changes to the environment and potential changes to production agriculture. One area of global change that has not been fully addressed is the potential changes to crop fertilizer N utilization. This study was conducted to examine the effects of soybean [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench.] CO2-enriched agro- ecosystem on plant nitrogen uptake and fertilizer N utilization in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study used a split-plot design replicated three times with two plant species as the main plots and two CO2 levels (375 and705 mu LL**-1 CO2) as subplots using open top field chambers over three years. Fertilizer application was made with **15N-depleted NH4N03 to act as a fertilizer N tracer. Soil solution samples were collected weekly at 90-cm depth and monitored for NO3-N leaching. Elevated CO2 increased total biomass and decreased N concentrations in both crops. In grain sorghum, elevated CO2 increased N uptake approximately 4%. In soybean, N uptake was increased approximately 25% with elevated CO2, due largely to an increase in N2 fixation. Elevated CO2 resulted in a significant decrease in NO3-N leaching below the root zone in both crops. No significant effect on fertilizer N utilization or loss was observed due to CO2 treatment but the nutrient utilization efficiency was increased for both crops, indicating better utilization of native soil N. This indicated that crops in a future elevated CO2 environment may be able to utilize available soil resources better to maintain productivity.