Microwave assisted biocidal extraction is an alternative method to measure microbial biomass of carbon from cultivated and non-cultivated soils
- 4 Downloads
Developing simple and cost-effective methods for soil microbial biomass carbon (MBC) measurement eases routine laboratory analysis and enables large numbers of soil samples to be measured in a relatively short period of time. Thus, the objective of this study was to develop a microwave-assisted biocidal-extraction (MWE) method which does not employ CHCl3 as biocide and K2SO4 as C-extractor, to estimate MBC. First, the microorganisms of soil samples are killed using microwave (MW) irradiation at energy level of 800 J g−1 soil as biocide followed by microwave irradiation extraction (MWE) at 562 W (120 J g−1 soil for 1 min), using deionized water as solvent. Microbial biomass of carbon from two contrasting soils microwaved with 80, 100, and 140 J g−1 soil did not differ from those obtained by using the chloroform fumigation-extraction (CFE) method with 0.5 mol L−1 K2SO4 as extractant. To evaluate the robustness of the MWE method, twenty-six soil samples, from cultivated and non-cultivated areas, with clay contents from 70–690 g kg−1, organic carbon from 5.52 to 50.82 g C kg−1 and pH values from 3.9 to 6.8 were analyzed for MBC using MWE and CFE methods. There was a linear regression (MW = − 17.87 + 0.92*K2SO4; R2 = 0.705; p < 0.001) between MWE and CFE. The biocidal microwave-assisted extraction method using 120 J g−1 soil for 1 min is a cleaner method for evaluating MBC, because it does not require chloroform, potassium sulfate salt and takes a shorter time to extract a set of soil samples.
KeywordsChloroform fumigation-extraction Extractable carbon Microwave extraction Microwave energy Soil microorganisms
The first author acknowledges a scholarship from National Council for Scientific and Technological Development (CNPq) at the Universidade Estadual de Maringá (UEM), PR, Brazil. This work was partially supported by the National Council for the Improvement of Higher Education (CAPES, 001). DSA is also research fellow of CNPq (312996/2017-9).
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Janksyn Bertozzi, Diva S. Andrade, and João Henrique Caviglione. The first draft of the manuscript was written by Janksyn Bertozzi, Cláudio C. Oliveira, and Diva S. Andrade and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 13.Haney RL, Franzluebbers AJ, Hons FM, Hossner LR, Zuberer DA (2001) Molar concentration of K2SO4 and soil affect estimation of extractable C with chloroform fumigation-extraction Soil Biology. Biochemistry 33:1501–1507Google Scholar
- 24.Nelson DW, Sommers LE (1982) Total carbon, organic carbon and organic matter. In: Page AL, Miller RH, Keeney D (eds) Methods of Soil Analysis, 2nd, vol 2. Am Soc Agron, Madison, pp 539–594Google Scholar
- 27.Reyes-Escogido L, Balam-Chi M, Rodrıíguez-Buenfil I, Valdes J, Kameyama L et al (2010) Purification of bacterial genomic DNA in less than 20 min using chelex-100 microwave: examples from strains of lactic acid bacteria isolated from soil samples. Antonie van Leeuwenhoek 98:465–474. https://doi.org/10.1007/s10482-010-9462-0 CrossRefPubMedGoogle Scholar
- 31.SAS II (1999) SAS/ STAT user’s guide Cary, N C, USA 12:Cary, N. C, USA. SAS Institute IncGoogle Scholar
- 36.Vance ED, Brookes PC, Jenkinson DS (1987b) Microbial biomass measurements in forest soils: determination of KC values and test of hypoteses to explain the failure of the chloroform fumigation-incubation method in acid soils. Soil Biol Biochem 19:689–696. https://doi.org/10.1016/0038-0717(87)90050-2 CrossRefGoogle Scholar
- 42.Xiao D, Xiao S, Ye Y, Zhang W, He X et al (2019) Microbial biomass, metabolic functional diversity, and activity are affected differently by tillage disturbance and maize planting in a typical karst calcareous soil. J Soils Sediments 19:809–821. https://doi.org/10.1007/s11368-018-2101-5 CrossRefGoogle Scholar