Methods of soil organic carbon determination in Brazilian savannah soils

Abstract

Several methods exist for determining soil organic carbon, and each one has its own advantages and limitations. Consequently, a comparison of the experimental results obtained when these methods are employed is hampered, causing problems in the comparison of carbon stocks in soils. This study aimed at evaluating the analytical procedures used in the determination of carbon and their relationships with soil mineralogy and texture. Wet combustion methods, including Walkley-Black, Mebius and Colorimetric determination as well as dry combustion methods, such as Elemental and Gravimetric Analysis were used. Quantitative textural and mineralogical (kaolinite, goethite and gibbsite) analyses were also carried out. The wet digestion methods underestimated the concentration of organic carbon, while the gravimetric method overestimated. Soil mineralogy interfered with the determination of carbon, with emphasis on the gravimetric method that was greatly influenced by gibbsite.

Soil Organic Carbon Determination Using NIRS: Evaluation of Dichromate Oxidation and Dry Combustion Analysis as Reference Methods in Multivariate Calibration

“…2 In addition, the recent adoption by the Brazilian government to the 'ABC program' (Agriculture Low Carbon), which aims to fund projects producers to adopt conservation systems with positive balance of carbon stock in soil, increases the need to monitor the soil carbon changes. 3 Soil analysis laboratories, located in Brazil, determine SOC based on analytical methods usually employed in the form of dichromate oxidation of carbon, with varying adaptations, 3 or dry combustion analysis. The Brazilian Agricultural Research Corporation (EMBRAPA) has created a near infrared (NIR) spectroscopy network to develop, validate and implement this technique as a routine method for determination of several chemical parameters in agricultural matrices as soil 4 and SOC is an interest parameter to be determined.…”

Predição de fósforo, carbono e nitrogênio em solos de basalto, por meio de espectroscopia NIR

“…Os maiores teores de C-CHNS se justificam pela oxidação das frações orgânicas e inorgânicas do C presentes nas amostras (McCarty et al, 2010), enquanto a oxidação do C pelo método Walkley & Black não é completa, pois o dicromato de potássio promove a oxidação parcial do C, entre 60 e 86% do total, e não contempla a fração inorgânica do C ou ao C protegido por uma fração mineral (Sato et al, 2014).…”

“…Resultados da etapa de calibração do modelo de predição para carbono elementar (C-CHNS), carbono orgânico (C-W&B), e N total, em amostras de solos desenvolvidos de basalto, com partículas menores do que 2,0 mm (A, B, C, D, E) e 0,2 mm (F, G, H, I, J). da oxidação parcial do C, proporcionada pelo método Walkley & Black (Sato et al, 2014), o que torna a relação dessa fração com os comprimentos de onda mais suscetível à influência da umidade e da mineralogia do solo, nos comprimentos de onda próximos de 1.400, 1.900, entre 2.100 e 2.200, e os próximos de 2.400 nm.…”

Priming effects of leaves of Laurus nobilis L. and 1,8-cineole on carbonmineralization

“…Soil texture was determined by Bouyoucos hydrometer (Beretta et al, 2014), field capacity (%) by 1/3 atmospheric pressure with a vacuum pump (Kacar, 2012), pH by a 1:2.5 soil-water suspension with pH-meter (inoLab pH/Cond 720, WTW GmbH, Weilheim, Germany) (Kacar, 2012), CaCO3 content (%) by a Scheibler calcimeter (Kacar, 2012). Organic C and total N contents of soils and leaves (%) were determined by modified Walkley and Black method and Kjeldahl method, respectively (SaezPlaza et al, 2013;Sato et al, 2014).…”