Groundwater quality monitoring for agriculture irrigated in Catol Do Rocha, Paraba State, Brazil

The electrical conductivity and of cations (Ca2+, Mg2+, Na+ and K+) and anions (Cl-, CO32-, HCO3- and SO42) contents of the water an Amazon well, from State University of Paraiba, Catole do Rocha city, Paraiba State, Brazil, located in the semi-arid region of the Brazilian High Sertao were evaluated monthly from January to December of year 2017. Despite the increase in electrical conductivity from 0.89 to 1.16 mS cm-1 and sodium adsorption ratio (SAR) from 4.43 to 10.45 (mmol L-1)1/2 did not change the water quality to agriculture. With mean risk to saline (C2) and low risk to exercise sodicity at soil (S1), toxicity and nutritional imbalance to plants, the concentration of dissolved salts increased from 0.57 to 0.74 g L-1 between rainy and arid periods. This situation expresses a high increase of almost 30% in the total dissolved salts during the evaluated period and shows the need for systematic monitoring. Simulating the irrigation with a 400 mm blade of this water with 1.16 dS m-1, in 120 days, can add to soil 2,970 kg ha-1 of salts, of which 1,892; 633; 258 and 143 kg ha-1 are of the sodium, calcium, potassium and magnesium species, respectively. Key words: Water quality, ionic components of water, salinity of water in well.