Microbial biomass-C determined using CaCl<sub>2</sub> and K<sub>2</sub>SO<sub>4</sub> as extraction reagents
Růžek, L. | Nováková, M. | Voříšek, K. | Skořepová, I. | Vortelová, L. | Kalfařová, Z. | Černý, J. | Částka, T. | Barabasz, W.
Microbial biomass-C [MBC] was determined by re-hydration [RHD] technique using two very similar salt solutions in dissociation potency (0.5 mol/l K<sub>2</sub>SO<sub>4</sub> [MBC-K] and 0.01 mol/l CaCl<sub>2</sub> [MBC-Ca]) in forest, grassland, arable Cambisols [Inceptisols] and Podzols [Spodosols]. MBC-Ca ranged from 254 to 5076 mg/kg dry soil (1.2–4.0% of C<sub>org</sub>). 114 soil samples were examined in the years 2002 and 2003. Organic C compounds extracted by 0.5 mol/l K<sub>2</sub>SO<sub>4 </sub>[EC-K] and 0.01 mol/l CaCl<sub>2</sub> [EC-Ca] increased in sequence: (1) arable Cambisols (100%), (2) cut and grazed grasslands (547%), (3) forest mineral horizon A<sub>H</sub>: 0–50 mm (783%) and (4) Norway spruce forest floor (2421%). The ratio EC-Ca/EC-K reached on average 62% and ranged from 48% to 74%. Correlation between EC-K and EC-Ca values is connected with soil organic matter status; the correlation was very close for Cambisols (r<sup>2</sup> = 0.925), a medium correlation was found for forest floor (r<sup>2</sup> = 0.380) and a weak correlation was observed for Podzols (r<sup>2</sup> = 0.042). The correlation between MBC-K and MBC-Ca was very close in all cases: Cambisols (r<sup>2</sup> = 0.811), Podzols (r<sup>2</sup> = 0.904) and forest floor (r<sup>2</sup> = 0.496). The ratio between organic carbon and organic nitrogen in 0.01 mol/l CaCl<sub>2</sub> extracts [EC-Ca/N<sub>org</sub>] could be declared as a new indicator for soil microbial association status.
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