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.
Highlights
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
Summary
In the practical field work in Finland the method adopted by von Post [9] is most commonly used for the determination of the degree of humification. Kivinen [5] has reported data for the C/N ratio in 88 peat samples for which the degree of decomposition by von Post is given This material offers an opportunity to compare the H- and C/N-values statistically. In the absence of an absolute standard for comparison no valid conclusion can be drawn on the reliability of the different conventional methods for the determination of the degree of humification This lack of a standard is due to an analytical defectiveness but it arises mainly from the fact that differences in the original raw material and in the conditions under which the decomposition takes place lead to products which vary to a great extent. Attention must be paid to possibilities offered by rapid and simple methods
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