Partitioning CO2 respiration among soil, rhizosphere microorganisms, and roots of wheat under greenhouse conditions

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).