INVESTIGADORES
BUSCHIAZZO Daniel Eduardo
artículos
Título:
Cation exchange capacity and specific surface area of soils with different clay mineralogy of the semiarid Argentina.
Autor/es:
HEPPER EN; BUSCHIAZZO, D.E.; HEVIA, G.; URIOSTE, A.; FERRAMOLAS, L.
Revista:
GEODERMA
Editorial:
Elsevier
Referencias:
Año: 2006 vol. 135 p. 216 - 223
ISSN:
0016-7061
Resumen:
The loessical soils of the semiarid Argentinean Pampas (SAP) contain variable amounts of volcanic ashes. Their influence on the mineral composition and some physicochemical properties of soils like soil specific surface area (SSA) and cation exchange capacity (CEC) have been still not elucidated. Because of that we analyzed 24 topsoil samples (0 to 20 cm) of soils with high and low volcanic ashes contents for clay mineralogy and its influence on soil chemical and physical properties and CEC and SSA. Results showed that ash enriched soils were placed to the south and ash free soils to the north-east of the SAP in agreement with the volcanic ash deposition pattern of 1932 Quizapu vocano eruption. Mineralogy of the clay fraction was dominated by amorphous minerals and less crystallized and expansible smectites in ash enriched soils, and by illites in ash free soils. No differences in crystallinity or expansibility were found between montmorillonites of ash free and ash enriched soils. Fine sized clays (b0.2 ìm) were dominated by illites and illite–montmorillonite intergrades in ash free soils and by amorphous materials in ash enriched soils. Such results indicated that montmorillonites tend to form more when volcanic ashes are present but their crystallinity and expansibility do not change with ashes content. SSA was positively related with silt contents in both ash free and ash enriched soils (r2=0.70, pb0.05). The clay fraction (b2 ìm) explained only 9% of SSA variability and the fine clay fraction (b0.2 um) did not affect SSA. The influence of silt on SSA was attributed to the existence of 2:1 minerals in the silt fraction. These results also indicated that ash contents did not influence SSA. CEC correlated positively with clay (R2=0.67, pb0.001) in ash enriched soils, and with organic matter in ash free soils (R2=0.837, pb0.001) but it did not correlate with fine clay contents in any of both soil types. These trends were explained on the basis of the higher CEC conferred by smectites in ash enriched soils and by OM in ash free soils. It can be deduced that soil degradation processes producing losses of fine sized particles, like wind or water erosion, will decrease SSA in both the ash enriched and the ash free soils, but only CEC in ash enriched soils. Organic matter losses due to excessive cultivation will decrease CEC in ash free soils.b0.2 ìm) were dominated by illites and illite–montmorillonite intergrades in ash free soils and by amorphous materials in ash enriched soils. Such results indicated that montmorillonites tend to form more when volcanic ashes are present but their crystallinity and expansibility do not change with ashes content. SSA was positively related with silt contents in both ash free and ash enriched soils (r2=0.70, pb0.05). The clay fraction (b2 ìm) explained only 9% of SSA variability and the fine clay fraction (b0.2 um) did not affect SSA. The influence of silt on SSA was attributed to the existence of 2:1 minerals in the silt fraction. These results also indicated that ash contents did not influence SSA. CEC correlated positively with clay (R2=0.67, pb0.001) in ash enriched soils, and with organic matter in ash free soils (R2=0.837, pb0.001) but it did not correlate with fine clay contents in any of both soil types. These trends were explained on the basis of the higher CEC conferred by smectites in ash enriched soils and by OM in ash free soils. It can be deduced that soil degradation processes producing losses of fine sized particles, like wind or water erosion, will decrease SSA in both the ash enriched and the ash free soils, but only CEC in ash enriched soils. Organic matter losses due to excessive cultivation will decrease CEC in ash free soils.