ABSTRACT


WALDO ESPINOZA G.1
 

A research on the detection of allophane in sorne soils of the Ñuble province was carried out at the Soil Science Dept. of the University of Concepción at Chillán, Chile.
The method proposed by Fieldes (1966) in order to detect the release of OH-ions, from amorphous structures (allophane) present in the soils, in the presence of suitable amounts of NaF, it is adaptable to the soils predominant in the Nuble province. The method detects the presence of allophane on those soils named "trumaos", Arrayán and Santa Bárbara, which release OH-ions above 10 x 10-5 mole OH-/lt. after 60' contact with NaF 0,5 M, pH 7,5.
The method revealed absence of structures like allophane in the following soils: San Carlos, Colorado, Mininco, Arenales, Cauquel1es and Mañil which release OH-ions below 1 x 10-5 mole OH-/lt.
Data showed that soils derived from old volcanic ash (Colorado, Mininco, Mañil) no longer contain allophane but crystalline clay minerals.
The proposed method is rapid and suitable for routine analysis when the knowledge of the clay fraction is needed.
The author condudes that additional techniques are needed in order to assert the clay mineralogy of the soils of the Ñuble province (Chile).

Keywords:
1 Ingeniero Agrónomo M. S. Profesor Departamento de Suelos, Facultad de Agronomía, Universidad de Concepción