Partitioning CO₂ Respiration among Soil, Rhizosphere Microorganisms, and Roots of Wheat under Greenhouse Conditions

Abstract

The measurement of soil, root, and rhizomicrobial respiration has become very important in evaluating the role of soil on atmospheric carbon dioxide (CO₂) concentration. The objective of this study was to partition root, rhizosphere, and nonrhizosphere soil respiration during wheat growth. A secondary objective was to compare three techniques for measuring root respiration: without removing shoot of wheat, shading shoot of wheat, and removing shoot of wheat. Soil, root, and rhizomicrobial respiration were determined during wheat growth under greenhouse conditions in a Carwile loam soil (fine, mixed, superactive, thermic Typic Argiaquolls). Total below ground respiration from planted pots increased after planting through early boot stage and then decreased through physiological maturity. Root‐rhizomicrobial respiration was determined by taking the difference in CO₂ flux between planted and unplanted pots. Also, root and rhizomicrobial respirations were directly measured from roots by placing them inside a Mason jar. It was determined that root‐rhizomicrobial respiration accounted for 60% of total CO₂ flux, whereas 40% was from heterotrophic respiration in unplanted pots. Rhizomicrobial respiration accounted for 18 to 25% of total CO₂ flux. Shade and no‐shoot had similar effects on root respiration. The three techniques were not significantly different (p>0.05).

Keywords:

• Heterotrophic respiration
• root and microbial respiration
• separation methods
• wheat

Acknowledgments

This research was supported by the U.S. Department of Energy's National Institute for Global Environmental Change (NIGEC) through the NIGEC Great Plains Regional Center at the University of Nebraska—Lincoln (The Department of Energy (DOE) Cooperative Agreement No. DE‐FC03‐90ER610100) and United States Department of Agriculture/Cooperative State Research, Education, and Extension Service (USDA/CSREES) (Agreement No. 2001‐38700‐11092) through funding for the Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS). Financial support does not constitute an endorsement by DOE of the views expressed in this article. Contribution No. 05‐129‐J of Kansas Agriculture Experiment Station.