Caracterização de águas e de solos do município de Congo, PB, microrregião do cariri ocidental.

Abstract

The research was carried out to evaluate the quality of waters used in agricultural areas of Congo region, Paraiba State, Brazil for the human consumption and in the irrigation and to characterize soils of the irrigated and no irrigated areas of the related region. The water and soil samples had been collected in two periods of the year, in other words, in the rainy period (May/2006) and in the dry period (December/2006). Water samples collected in Cordeiro dam, in wells and in river, were analyzed according the described methodology in APHA (1998), and the soil samples collected in the depths of 0 - 20 and 20 - 40 cm (rainy period) and in the depths of 0 - 5 and 5 - 20 cm (dry period) were analyzed with base in the described methodology in Richards (1954) and EMBRAPA (1997). The CEw and other chemical characteristics increased in the dry period, except pH, whose variation was small. The chemical composition of all waters was similar, being predominantly chloride and sodic, in both periods, except waters of low salinity, which had relatively high bicarbonate concentrations. In average terms, as much in the rainy period as in the dry period, the waters of the wells presented more salt of what the waters of the dam and the river. In agreement with CONAMA/MS/OMS Resolution and with the results of pH, cations and anions, more of 60% the waters collected in both the periods of this study, are considered proper for human consumption. According to Richards's classification, in dry period in 56,25% of waters used for irrigation the salinity varied of high the very high, while in this same period, 6,25% of waters presented risk of medium sodium. On the other hand and according to Ayers and Westcot's classification about 2/3 of waters must be used only for irrigation of salt or ions Na+ and CI" tolerant cultures. In relation to the fertility the soils presented high Ca++, Mg+ + , K+ and P concentrations in both periods and areas of study, not existing deficiency of these elements for the plants. As the MO, will be necessary the application of the same, once in the irrigated areas, in both periods, medium tenors prevailed. In relation to the soils salinity, in the two periods and the two study areas predominated normal soils. On the other hand, in the rainy and dry period predominated no sodic and middling sodic soils, respectively.