The Carbon-Organic Matter Factor in Various Soil Types

The estimation of organic matter in soils has followed various fashions, the oldest and simplest method being the measurement of loss on ignition which has been replaced, for certain purposes, by the determination of organic carbon which is multiplied by an accepted factor to obtain the estimate of organic matter. From the latter part of the nineteenth century onwards it has been a frequent practice to use a value of 1.724 for the conversion factor, based on the assumption that the organic matter contains 5800 carbon (Cf. LUNT, 1931; BROADBENT 1953; READ and RIDGELL 1922). If there were unequivocal evidence that the carbon content of soil organic matter was constant this method would no doubt be acceptable. The question of the carbon-organic matter factor has arisen again from some analyses that have been made of the organic matter of some natural British soils of definable ecological types: mull, mor, fen, and bog. In the present paper some of the simpler results of this survey are briefly discussed, in order to focus attention on some of the problems involved in the use of such a factor.