Manejo da salinidade em irrigação localizada : análise da alternativa de lixiviação incompleta

Abstract

The present study was developed in an alluvial valley (NEOSSOLO FLÚVICO) with shallow water table, in the Nossa Senhora do Rosário Farm, in the municipal district of Pesqueira - PE (semi-arid Northeast), where salinization risk exists, specially with the practice of irrigated agriculture, due to the quality of the available groundwater. Within the experimental area it was selected for study an irrigated plot with drainage installed. In the irrigated lots of the valley, the salinity management is usually based on the leaching, which transports salts to the aquifer, which can deteriorate groundwater quality, specially with insufficient circulation and shallow water table exists. The main objective was to evaluate the efficiency (potential) of the irrigation management based on the partial leaching of salts in a plot irrigated with saline water and to characterize the behavior of the flow of water as well as the movement of salts when subject to the irrigation management proposed. Tensiometric Stations were installed and monitored, allowing the recording of the matric tensions in the root zone. Electrical conductivity of the irrigation water and the soil water, were monitored, through the method of the saturated paste in laboratory. The groundwater piezometric level was monitored through observation wells, which also allowed monitoring of the quality of the groundwater. Based upon the climatological data, the physical characteristics, hydraulicbehavior of the soil, and in the crop characteristics, it was possible to approximately reproduce with numerical modelling the experimental field results, allowing simulations related to soil salinity. For the 0 -100 cm profile it was observed a decrease in the electrical conductivity after the irrigation applications, specially in the root zone, both in the field observations and in the simulated scenarios. It was verified, through modeling, that the alternative of complete leaching did not improve the effective washing of the profile when compared to the incomplete leaching.