ABSTRACT
Soil light organic matter fraction of a volcanic soil under different agronomic management as an indicator of changes in labile organic matter

Erick Zagal1, Nicasio Rodríguez2 Iván Vidal2 y A. Bárbara Flores3
 

Starting from an 18-year experiment with different crop rotations, samples of soil of volcanic origin from the foothills of Ñuble (37º09’ S lat.; 72º02’ W long.) were obtained in order to determine the effect of agricultural management on light fraction (FL) of the organic matter. FL was separated by density using NaI (d = 1,8 g cm-3). Carbon (C) and nitrogen (N) contents were determined by dry combustion both in the whole soil and the isolated FL. Light fraction contents were higher than those found in other research with non-volcanic soils. However, a clear trend to decrease FL was observed when soil use was intensified. The C or N proportions of the soil and the FL presented similar results. The use of this fraction as a sensitive indicator of changes in labile organic matter produced by different agricultural management is discussed.

Keywords: soil physical fractionation by density, NaI, C, N, volcanic ash soils, andisols
1 Universidad de Concepción, Facultad de Agronomía, Departamento de Suelos, Casilla 537, Chillán, Chile, E-mail: ezagal@udec.cl
2 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación Quilamapu, Casilla 426, Chillán, Chile.
3 Tesis Ingeniero Agrónomo, Universidad de Concepción, Facultad de Agronomía, Departamento de Suelos, Casilla 537, Chillán, Chile.