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Title: Composition and distribution of the organic matter in some typical soil profiles from the north-east of Scotland
Author: Shewan, James Mackay
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1935
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The present day knowledge of the nature and amount of the organic matter in forest soils is not very extensive, due chiefly to the empirical and arbitrary methods frequently employed by investigators rather than to neglect of the subject. The recently advocated method of proximate analysis (the Waksman method), which appears to offer many advantages over the older emperical procedures, has been used as a basis for the investigation of five forest and heath soil profiles from the North East of Scotland. For the determination of the Total organic matter in soils a modified Chromic Acid wet combustion method was devised, which gives excellent results both with pure substances and with soils when compared with either theoretical or dry combustion values. After thorough investigation, it has been found that the acid residue from this wet combustion is less satis-factory for nitrogen determinations than is the usual Kjeldahl method. The Waksman method of proximate analysis has been thoroughly tested, more particularly with regard to hemi- cellulose and cellulose determinations, and a modified procedure is recommended. The/ The study of the nature of plant and soil hemicellu- loses has shown the inaccuracy of the single determination of waksman and the need for a more precise definition of Hemicelluloses than that used by this author. Cellulose determinations made by the usual chlorine-ation method have sometimes shown wide discrepancies when compared with the hydrolytic method adopted by waksman, and an attempt has been made to explain these. The modified system of proximate analysis was then applied to the selected soil profiles. Differences in the composition of the newly fallen leaves and needles of the different profile have been demonstrated. These are reflected in the changes taking place during decomposition and humification as well as in the subsequent alteration products throughout the whole profile. These differences are discussed in the light of present day theories regarding soil organic matter, its nature, formation and role in soil-forming processes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available