Kwantitatieve aspecten van humusopbouw en humusafbraak

J. Kortleven

Research output: Thesisinternal PhD, WU

Abstract

Some common expressions on humus were current that were not based on exact or quantitatively analysed data.
To achieve a desirable humus content, it was necessary to know the relation between supply of humus and humus content, here studied, and the relation between humus content and productivity.

A field trial begun in 1911 to compare complete fallow with normal exploitation indicated two axioms: from a supply of crude organic matter a certain constant part became humus each year; from humus in soils a certain constant part was mineralized each year.

If supply was equal each year it was possible to derive the following formula for the rise or fall in humus content: y = y m - (y m - y 0 ) (1 - K 2 ) t, where y = humus content, y m = humus content at ultimate equilibrium,y 0 = initial humus content, K 2 = rate of mineralization (see axiom 2), and t = time in years. Further y m = K 1 /K 2 x, where K 1 = rate of humification (see axiom 1), and x = supply with raw organic material.

These formulae were tested in the few available experiments, suitable for the purpose (which did not include the classical Rothamsted fields). K 1 was 0.4; thus 40 % of the supply becomes humus each year. K 2 had values between 0.015 and 0.02; from this it followed that 2 % of the humus was yearly mineralized. No difference was yet found in the value of either coefficients for different organic materials and in different soils.
Original languageDutch
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Schuffelen, A.C., Promotor, External person
Award date31 May 1963
Place of PublicationWageningen
Publisher
Print ISBNs9789022000854
Publication statusPublished - 1963
Externally publishedYes

Keywords

  • humus
  • humus horizons
  • litter (plant)
  • soil chemistry

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