Determination of the degree of humification in peat samples

Authors

• Armi Kaila University of Helsinki, Department of Agricultural Chemistry

DOI: https://doi.org/10.23986/afsci.71402

Abstract

The theoretical difficulties in the determination of the degree of humification in peat samples is discussed and the possibilities offered by some conventional methods are examined. A colorimetric method based on the extraction of air dry and ground peat samples with 0.025 M sodium pyrophosphate solution was compared with the direct examination of fresh samples by the method of von Post. A significant but not very high correlation was found between the data given by these two methods. It was supposed that colorimetric prodecures of this kind can only be used as supplements of other methods. A rather close correlation was found between the volume weights of air-dry and ground samples and the corresponding values determined by the method of von Post. Because of this result and in view of the fact that the volume weight is a quantity generally determined always when peat analyses are performed, it would offer a convenient basis for the estimation of the degree of humification. Since the material studied contained only some very well humified samples the applicability of the volume weight to the determination of the degree of decomposition of this kind of samples was not proved. A simple scale of humification based on the volume weight was adopted. Its basic unit was 0.08 or the volume weight obtained for the undecomposed plant material collected from various kinds of peat land. It depends, of course, on the method employed for the determination of the volume weight. The elimination of the effect of the ash content of these virgin peat samples did not significantly improve the correlation of the H-values and the volume weights. The material of this investigation consisted of 220 samples collected from various depths of virgin peat soils.