ABSTRACT
Microbial activity in a volcanic ash soil under different agricultural management

Erick Zagal1, Nicasio Rodríguez2, Iván Vidal1 y Lorena Quezada3
 

The microbial activity of a volcanic soil of the Central Valley (Typic Melanoxerand) was measured at the end of a 7 years-old experiment in 6 crop rotations with different agricultural management and soil use intensity. Undisturbed samples of this soil were incubated in laboratory by 30 days under temperature (25ºC) and moisture controlled conditions. C-CO2 mineralization was determined every 10 days and the N inorganic mineralization by quantifying its increment among days 0 and 30. At the same time, organic carbon (C) was determined in composite samples of the same essay. Quantification of C-CO2 mineralization was effectively more sensitive than organic C determination to rotation treatments and it evidenced changes early in the fertility of the soil. A significant correlation (P <0.05) was found between C and nitrogen (N) mineralization (r = 0.61) showing similar effects of agricultural management in both parameters. The organic matter content of the different rotations correlated significantly with microbial activity (mineralized C-CO2) confirming by this way the utility of this biological index in the evaluation of soil degradation in function of their use intensity.

Keywords: mineralized C, soil quality, mineralized N, crop sequence.
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.