Fjölrit RALA - 15.06.2004, Síða 58

the Acrudoxic Hydrudands (Azores). This is in agreement with results reported by Madeira et
al. (2003) for Andisols from the Azores. The values in Andisols were positively correlated
with both organic C (r=0.56; p<0.05) and Al0 (r=0.68; p<0.05) contents.
The values of CEC by the SM of the Andisols Ah horizons were positively correlated with
the organic C content (r=0.82; p<0.01), but not with the Al0 content. For B horizons, the
correlation of those values with Al0 content was stronger (r=0.77; p<0.01) than with organic C
content (r=0.64; p<0.05). Similar trend was observed for ACEC values (r=0.86; p<0.01;
r=0.60; p<0.05). Values of ECEC of subsurface horizons were negatively correlated
(r=-0.73; p<0.01) with Al0 content.
The values of exchangeable Ca were strongly variable among studied soils. Andisols with
high allophane content (and/or organic C contents), that is, Typic Hapludands and Acrudoxic
Hydrudands (Azores), and Alic Hapludands (France) showed the lowest values, especially in
the Bw horizons (0.40-0.56 cmolc kg"1). Similar pattem was observed for the exchangeable
Mg. These data corroborates results reported by Madeira et al. (2003) for Andisols from
Azores. Non-Andisols mostly showed higher contents of exchangeable Ca and Mg than
Andisols. Exchangeable K was very high in both Andisols (0.84-4.74 cmolc kg'1) and non-
Andisols (6.76-23.70 cmolc kg"1) from Italy; additionally, values in Andisols were mosdy
lower than in non-Andisols. Extractable A1 showed high values (3.89-7.60 cmolc kg"1) in the
surface horizons of Andisols from the Azores (both Haplic Hapludands and Acmdoxic
Hydmdands) and France (Alic Hapludands).
The values of anion exchange capacity (AEC) determined by the CE, that is, at field pH
conditions, showed strong differences according to soil types. Those values were very low
(<0.54 cmolc kg'1) or null for non-Andisols. Values for Andisols varied from 0.25-0.84 cmolc
kg"1 (Eutric Fulvudands) to 4.09-15.45 cmolc kg"1 (Acmdoxic Hydmdands). Correlations
between the AEC values and the organic C and Al0 contents were not observed. The ratio
AEC/CECce was generally less than one; this ratio was greater than 1 in Andisols from the
Azores, and in most of the horizons of Andisols from France.
Authors thank Fabio Terribili (Italy), Jorge Pinheiro (Azores, Olafur Amalds and Hlynur
Oskarsson (Iceland), Marisa Tejedor and José Hemandez-Moreno (Tenerife), A. Economou
(Greece), Toine Jongmans and Peter Buurman (The Netherlands), Folkert Van Oort, Paul
Quintin and Martine Gérard (France), G. Fuleky, A Kertesz, B Marasz and O. Feher
(Hungary) for the selection of COST 622 profiles and/or the soil and site description, Otto
Spaargaren for Soil Classification (Soil Taxonomy), and Isabel Meireles and Ana Batista for
technical assistance.
References
Gillman, G. P. and Sumpter, E. A. 1986. Modification to the compulsive exchange method for
measuring exchange characteristics of soils. Australian Joumal of Soil Research 24: 173-
192.
M. Madeira, E. Auxtero and E. Sousa 2003.Cation and anion exchange properties of Andisols
from the Azores, Portugal, as determined by the compulsive exchange and the ammonium
acetate methods. Geoderma 117: 225-241.
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