Propriétés des complexes humiques dans différents types de sols

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Title: Propriétés des complexes humiques dans différents types de sols
Author: Duchaufour, Philippe
Abstract: SUMMARY. The method for fractioning -various humus complexes, which isdescribed in this paper, is essentially based on the differences betweentheir physical properties. especially their degree of dispersion, theirsensibility to the action of electrolytes and the nature of their associationwith the mineral colloids It has been thus possible to separatethree main groups of complexes.The pre-humus complexes are dispersed, and the nearest to certinoriginal constituents of the vegetal tissues, and not easily decomposed.As they are soluble in the acetyl bromide, different inthat from the true humic acids, it was possible to appreciate themattantitatively.The a complexes (brown humic acids) are still lightly coloured andloosely tied to clay. They can be extracted by means of dilute soda.even when clay is flocculated. therefore in the presence of KC1 inthe sodic solution.The b complexes (grey humic acids) are much darker and closelytied to clay. They can be ext-acted by dilute soda only when clayis completely dispersed, consequently in the absence of KC1. Besides,they are only partly soluble in soda, but this solubility seems to beincreased by a preliminary treatment with acetyl bromide.These three groups of complexes are found in variable proportionthe different humus types. The pre-humus compounds characterizethe « Mor », which is slowly decomposed. Being very muchdispersed, they move in the soils and accumulate in a rather largequantity in the B horizon of the humuspodsols. They seem to be thee,sential agents of podsolisation.The a complexes are predominant in the « Mull », not very acidand rapidly decomposing-. They g,ive to the brown forest soils. orto the g-rey brown podsolic soils, a somewhat unstable structure,which favours the eluviation of clay under the action of outer dispersing-influences (leaching).At last, the b complexes can be estimated at about 50 % of thehumic matter in renclzina soils, rich in lime. They are responsiblefor the very stable agg,regated structure, which characterizes thesesoils and prevents the leaching of the colloidal elements. The prehumuscomplexes seem to be inexistent in the soils, with a sufficientlyhigh microbian activity.(Traduction M. GROSDIDIER.)
Publisher: ENEF, Ecole nationale des eaux et forêts, Nancy (FRA)
Date: 1954

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