rapid microwave digestion method for colorimetric measurement of soil organic carbon

• Published in: Communications in soil science and plant analysis 1998-01, Vol.29 (15/16), p.2269-2284
• Main Authors: Islam, K.R, Weil, R.R
• Format: Article
• Language: English
• Subjects: acid treatment; Agronomy. Soil science and plant productions; Biological and medical sciences; carbon; Chemical, physicochemical, biochemical and biological properties; determination; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Geochemistry; microwave treatment; Organic matter; oxidation; Physics, chemistry, biochemistry and biology of agricultural and forest soils; soil analysis; Soil and rock geochemistry; soil organic matter; Soil science; spectroscopy
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1080/00103629809370110

Soil organic matter is an active component of agroecosystems. Rapid and precise measurement of organic carbon (C(org)) is essential to monitor changes in organic matter and soil quality. A new semi-micro wet digestion method for the determination of C(org) was developed using rapid microwave energy applied at 500 J mL(-1) digestion mixture to enhance oxidation of C(org) by K2Cr2O7 and conc. H2SO4. This proposed method and three existing methods of soil C determination were compared with the LECO dry combustion carbon analyzer. The r(2) value for the proposed microwave method regressed against LECO C was 0.9913. The recovery of C(org) by the rapid microwave digestion method for spectrophotometric measurement was 91.7 +/- 1.2% (conversion factor 1.09) of C measured by the LECO dry combustion method. Compared to the traditional Walkley-Black's method, the proposed spectrophotometric with microwave digestion method was rapid and more precise, used smaller reagent volumes, and produced less waste.