Movimiento de nitrato en un suelo volcánico bajo diferentes regímenes de riego

Abstract

The effect of the irrigation regime on the nitrate movement by mass flow was studied in a volcanic ash soil. Three nitrate treatments, (0, 80 and 160 Kg N/ha) and five irrigations heads (2, 4, 8, 12 and 16 cm) werw used under field conditions. In the laboratory, undisturbed soil columns were submitted to two nitrate treatments (80 and 160 Kg N/ha) and three water heads (4,8 and 12 cm). Under field conditions, it was found that nitrate losses amounted to 92 per cent in a 42-day period in a 45-cm. In a 24 hours period, it was observed that nitrate dissapearance form the 5-cm depth increased with the irrigation head in a linear fashion from 4 to 12 cm of water. Laboratory results indicated that the nitrate loss from the 45-cm profile observed in the field could not be caused by mass flow alone and most probably by denitrification. A linear relationship was found between nitrate advance and irrigation head for the 160 Kg N/ha application, moving down at an advance rate of 2.5 cm for every cm of applied water. This relationship was curvilinear for the 80 Kg N/ha application indicating that nitrate movement depends upon the applied quantity. Normal irrigation heads in these soils do not cause nitrate displacement further than 20 cm, but the effect of several irrigation cycles on the nitrate movement is still unknown.