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Small Scale Heterogeneity of Soil Chemical Properties. I. A Technique for Rapid Aggregate Fractionation
Author(s) -
Kayser Achim T.,
Wilcke Wolfgang,
Kaupenjohann Martin,
Joslin John D.
Publication year - 1994
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19941570610
Subject(s) - fractionation , sieve (category theory) , fraction (chemistry) , aggregate (composite) , sieve analysis , soil water , mineralogy , chemistry , soil science , environmental science , chromatography , materials science , mathematics , nanotechnology , combinatorics
Several recent studies have observed physical, chemical and microbiological heterogeneities on the scale of soil aggregates. The publications emphasize the ecological importance of these small scale gradients. This paper introduces a method for the rapid fractionation of soil structure units into a surface fraction and a core fraction. The technique combines a rapid freezing in liquid N 2 and standardized wet sieving of the structure units. During the sieving process the aggregate surfaces begin to thaw and are consequently washed through the sieve. The soil passing the sieve during a specified time is termed aggregate surface fraction, the remainder is the aggregate core fraction. Samples from 18 forest soil profiles were taken to study the precision and accuracy of the method, as well as factors determining the efficiency of fractionation. The precision of aggregate fractionation as determined by parallel fractionations yielded coefficients of variability of 5.3 to 7.5% and 6.5 to 11.4% for the amount of core and surface fraction, respectively. Furthermore, the proposed technique yielded results comparable to those obtained by manual razor‐peeling of the aggregate surfaces. The variation of concentrations of chemical parameters in water extracts of both aggregate fractions was up to six times greater than in soil solutions obtained from mixed samples. Increasing soil organic C resulted in a decrease in the proportion of the aggregate surface soil collected under fixed sieving conditions, while clay content correlated positively with the amount of the aggregate surface fraction collected.