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CHEMICAL CHARACTERIZATION OF TWO ANDEPTS (TRUMAOS)OF THE ÑUBLE PROVINCE (CHILE): ARRAYAN AND SANTA BARBARA

Waldo Espinoza G.1 y Eduardo Riquelme F.2

The chemical characteristics of two Andepts soil associations from south-central Chile (36º36' L.S.) were studied: The Arrayan soils are found in the Central Depression (Central Valley) and the Santa Barbara soils found at the "piedmont" of the Andes Mountains range and closer to the active volcanic zone.
The study shows that the soils, in general, have similar chemical characteristics which makes it difficult to separate them for classification purposes.
Both soils can be considered as moderately acid, with pH values increasing with soil depth. As organic matter increasead so did soil acidity.
Organic matter and total-N values are very high. Moderate and highly variable NO3N values were not associated with organic matter content but to extractable Al values. NH4-N high values reveal anomalous N mineralization processes.
Phosphorus fixation values are very high in both soils and increased with extractable Al content and decreased as organic matter values increased.
The soils present low available P values. Also as P fixation increased available P values decreased. both soils show high cation exchange propierties and very low base saturation values dominated by Ca and Mg.

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1Ing. Agr., Ph. D., Profesor Departamento de Suelos, Escuela de Agronomía, Universidad de Concepción, Casilla 537, Chillán, Chile.
2Laborante, Departamento de Suelos, Escuela de Agronomía, Universidad de Concepción, Casilla 537, Chillán, Chile.

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