New aspects on the determination of soil‐specific respiration quotients of arable soils for the application in the barometric process separation technique

Abstract

AbstractBackgroundThe respiratory quotient, that is, the CO2–O2‐exchange ratio during aerobic heterotrophic soil respiration, (RQAHR) is one of the key variables of the barometric process separation (BaPS) technique. For reliable application, the BaPS method requires the adjustment of RQAHR to soil‐specific substrate conditions.AimThe objective of the present study was to determine RQAHR in five arable soils varying between pH 4 and 8 and carbon/nitrogen (C/N) ratios between 8.4 and 11.9 using the BaPS–15N method. Further, we aimed to elucidate whether RQAHR can be estimated from basic soil properties.ResultsDetermined RQAHRs were soil specific and ranged between 0.74 and 1.53. RQAHR particularly affected the calculation of gross nitrification rates but not soil respiration rates. Based on a multiple linear regression analysis, soil pH and the C/N ratio of the soil organic matter pool were identified to explain well (R2 = 0.984) the measured RQAHRs. Applying the thus derived RQMLR to the calculation procedure led to good agreement between gross nitrification rates derived by the 15N pool dilution technique.ConclusionsFuture studies are needed to test whether this empirical relationship between RQAHR, pH, and C/N ratio is generalizable. If this would be the case, the BaPS method could be applied without the use of a stable isotope and thus, being less resource demanding than the 15N pool dilution technique.