Humus: Origin, chemical composition, and importance in nature. SELMAN A. WAKSMAN


Humus: Origin, chemical composition, and importance in nature. SELMAN A. WAKSMAN

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Although the importance of humus in agriculture was recognized by
the early Greek and Roman philosophers, it is only during the last
century and a half that attempts have been made to disclose the nature
of this group of organic complexes, their formation and decomposition,
and their role in plant nutrition. Although a number of problems
concerned with the study of humus still await solution, sufficient evidence
has accumulated to warrant an attempt to summarize the
available information in a monographic manner.
Several reviews have been published dealing with certain aspects
of the origin, chemical nature, properties, and functions of humus.
It is of particular importance to note here Wollny's book "Die Zersetzung
der organischen Stoffe" published in 1897, Baumann's paper on
the "History of the humic acids" in 1910, Oden's monograph on "Humic
acids," several recent handbook summaries of chemical or agricultural
aspects of humus, as well as the numerous books on coal, peat, forest
soils, and composts. None of these, however, fully covered the subject
of humus as a whole. The approach to the problem has usually
been made either from a purely chemical, physico-chemical, agricultural,
or technological point of view. Wollny is about the only one
who has made an all-embracing study of humus as a natural body, of
its formation, and transformation. Unfortunately, soil microbiology
was still in its infancy at that time, and little was known concerning
the role of microorganisms in the formation of humus.