A comparison of three methods of organic carbon determination in some New Zealand soils

Abstract

A dry combustion (Dumas) reference method for measuring total organic C (T), is compared with two other methods: the wet acidified dichromate oxidation, Walkley-Black procedure (an estimator of organic C) and loss on ignition (L) (an estimator of organic matter) for 40 samples from various depths from five New Zealand mineral soils, spanning a range of textures and cultivation treatments. Regression analyses reveal the following:(1) an excellent linear relation exists for all samples between Walkley-Black procedure and reference method results, with a mean conversion factor 1.25, which compares with the original value 1.32 recommended by Walkley & Black (1934).(2) L and Tare less well-related by an equation of the form L = a+ bT. In contrast to the traditional assumption that b N 1.72 and a N 0, a strong 'intercept effect' (a > 0) is revealed,

Impact of intensive market gardening on the nutrient status of hydromorphic soil in the Ojo area of Lagos metropolis, Nigeria

“…The mean organic matter content of the 0-10 cm of the swamp forest control areas is similar to the level reported by Aweto (1981) for the surface layer of well-drained forest soil in south-west Nigeria. The mean level of organic carbon in the surface layer of the intensively cultivated hydromorphic soils in the study area is similar to that of an intensively cultivated soil in New Zealand studied by Grewal et al (1991), but higher than the levels in well-drained soil under shifting cultivation (Aweto, 1988), and under continuous cultivation for 3-7 years in south-west + Difference between means is significant at 5% confidence level. * Difference between means is significant at 1% confidence level.…”

Soil Organic Carbon: Relating the Walkley-Black Wet Oxidation Method to Loss on Ignition and Clay Content

“…When LOI and W-B is compared with the reference method (i.e. dry combustion), an excellent relation existed between them, with a mean conversion factor of 1.25, which compared well with the recommended value of 1.32 (Walkley and Black, 1934;Grewal et al, 2006). Over the years, there have been different regression equations and models developed for the estimation of SOC by various methods.…”

Répartition des anomalies pédogéochimiques en relation avec un indice polymétallique et une ligne à haute tension à courant continu, secteur de la rivière Pontax, Baie-James /

“…La méthode est basée sur le principe que, à la température choisie, tout le carbone organique est converti en CO2, tandis que les carbonates ne sont pas affectés. En fait, la perte de CO2 provenant des carbonates et la perte d'eau à partir des minéraux argileux sont considérées comme négligeables (Bisutti et al, 2004;Grewal et al, 1991;Soon and Abboud, 1991). …”