Caracterização da qualidade da água de irrigação da microrregião homogênea de Catolé do Rocha-PB (MRH-89).

Abstract

The objective of the study was to evaluate the quality of the irrigation water and its seasonal variations in eight municipalities of the Catole do Rocha homogenous microregion as well as to verify the influence of the irrigation water quality on some characteristics of the soils. For this, two water samplings were conducted, the first one in November 1980 (dry period) and the second in May 1981 (after the rainy season), in each sampling 150 surface and sub-surface water samples were collected. The analysis of the first sampling showed that 74.3 % of the studied waters are of good quality for irrigation, 20,9% have a high hazard of salinity and 4,8% are waters with a very high hazard of salinity and/or sodicity. The results of the second sampling showed a reduction in the salt concentration of the waters and thus an increase in the percentags of good quality waters (81,9 % ). On the other hand, a decrease of 4.0 and 3,6% was observed in waters with high and very high hazards of salinity, respectively. In both the samplings 8,0% of the water samples showed phytotoxic le_ vels of boron and undesireable concentrations of residual sodium carbonate were found to be present in 3% water samples. The Bom Sucesso municipality showed the best quality of irrigation water. With respect to the influence of the quality of the irrigation water on the chemical properties of the soil, a significant linear correlation was found between the sodium adsortion ratio of the saturation extract and the exchangeable sodium percentage of the irrigated and non-irrigated soils. Furthermore, in case of Irrigated soils, a slight increase of electrical conductivity of saturation extract in comparison / to adjacent non-irrigated soils was observed.