Respiratory quotient (RQ) is the ratio of CO2 produced to O2 consumed by an organism. Complete respiration of glucose will give an RQ of 1 as described by the formula CnH2nOn+nO2→nCO2+nH2O. The respiration of molecules with lower oxygen content, such as lipids, give RQ values of less than one, whereas in cases of anaerobic metabolism, an increase in biomass or the respiration of substances such as humic, oxalic and citric acids the respiratory quotient can be greater than one. In complex systems such as soil, Dilly (2003) found that the RQ varied dramatically, and changed within the same soil under varying conditions. Similarly, Hollender et al. (2003) found RQ was informative in determining the underlying metabolic mechanisms, such as nitrification processes. Dilly (2004), studied the effects of various organic compounds on RQ, and found that beech forest soils amended with cellulose or humic acid maintained RQ values greater than one for more than 20 days after application.
Measurement of RQ involves a simultaneous detection of the changes in CO2 and O2. The objective of this study was to demonstrate a technique to measure the RQ in a closed static system.
Nelson, Jake, "Measurement of the Respiratory Quotient of Peat" (2012). Hydroponics/Soilless Media. Paper 5.