Raúl Raggi M.1, Waldo Espinoza G.2 y Oscar Rojas U.3

A research on the leaching of soil NO3-N in a Andosol (Arrayán of the Ñuble province)(Chile 36º S) was conducted. Sugar beet (Beta vulgaris var. Sacharina) at different sodium nitrate rates (16% N) was used as a cover crop. Intensive and abundant irrigation was performed, throughout the growth period of the crop.
NH4-N and NO3-N content of the soil was evaluated by sampling the plots each month at the following depths: 0-25 cm, 26-50 cm, 51-75 cm and 76-100 cm and by using the steam destillation procedure of Bremner, after displacing NO3-N or NH4-N with 2N KCl.
Leaching of NO3-N or NH4-N in the Arrayán soil was not observed and this was indicated by an accumulation of mineral-N forms at the top 25 cm of the soil profile. this is attributed to allophane, the predominant clay-size minerals of these soils.
NO3-N content of the soil was highly variable throughout the growth period of the sugar beets. NH4-N, showed to be low copared to NO3-N content and highly constant throughout the growing season of the crop.
Soil and air temperature and sodium nitrate rates did not influence the NH4-N nor the NO3-N content of the soil.

1Ing. Agr., Actualemente: Ministerio de Agricultura.
2Ing. Agr., M. S., Ph. D., Profesor del Departamento de Suelos, Escuela de Agronomía, Casilla 537, Chillán, Chile.
3Ing. Agr., Especialista en Fertilidad de Suelos, IANSA.