Can Soil Carbonate Dissolution Lead to Overestimation of Soil Respiration?

Root and microbial respiration is considered to be the main source of CO2 production in soil; however, calcite dissolution in calcareous soils may contribute to the emitted CO2. The major aim of this research was to quantify the contribution of CaCO3 dissolution to CO2 emission from a soil with and without the addition of an organic residue. Emissions of CO2 and its delta C-13 from incubated noncalcareous (Golan Heights [GH], -26.23 parts per thousand) and calcareous (Bet She'an [BS], -11.47 parts per thousand) soils with and without the addition of a pasteurized chicken manure (PCM, -23.2 parts per thousand) were determined. During 56 d of incubation, 445 and 1804 mg kg(-1) CO2-C emitted from BS and GH soils, and PCM application caused additional emission of 2430 and 1884 mg kg(-1) CO2-C, respectively. The NO3--N concentrations in the control BS and GH soils were 46 and 133 mg kg(-1) and PCM application increased it to 508 and 577 mg kg(-1), respectively. The emitted CO2-delta C-13 from BS and GH soils were -20.0 +/- 0.2 parts per thousand and -27.2 +/- 0.09 parts per thousand and application of PCM changed it to -20.6 +/- 0.42 parts per thousand and -23.7 +/- 0.16 parts per thousand, respectively. Consequently, the contributions of the inorganic source to CO2-C emission from BS without and with PCM and from GH with PCM were 113.4, 417.5, and 176 mg kg(-1) (26.5, 14.5, and 5% of the total), respectively. We suggest that oxidation of organic matter, mineralization of organic N, NH4 nitrification, oxidation of organic S, and production of organic acids caused chemical dissolution of calcite and CO2 emission. Ignoring this process will result in overestimation of the respired C.