Risk of degradation in irrigated soil at the Distrito de Irrigação do Perímetro Araras Norte, Ceará, Brazil

Abstract

This research was done aiming to compare the salinity variation in the root zone, on long-term, under irrigation condition, with another one, in an undisturbed land. Also, it was evaluated the raifall effect in the salt lixiviation and the irrigation impact due to salts addition to the soil. Study was carried out in the grapevine orchard located at the Distrito de Irrigação do Perímetro Araras Norte (DIPAN), Ceará State, Brazil. The analyzed tributes were: electrical conductivity (EC), Ca2+, Mg2+, Na+, K+ e Cl-. Soil samples were taken in depths of 0 to 0.30 m; 0.30 to 0.60 m; 0.60 to 0.90 m and 0.90 to 1.20 m from May/2003 to September/2005 in site irrigation condition and another one, under undisturbed land. Site has been under irrigation condition since 2001. To evaluated irrigation impact and rainfall of the salt leaching was applied the independent-samples t-test for equality of means at 1% level of significance. Results showed that salt concentration to all depths its hight at the irrigation condition than that under undisturbed land. Magnesium ion showed the higher influence in electrical conductivity values and the chloride concentration was lower in the more depth layers. Rainfall was not enough to leach the salts added to soil by irrigation at 1% level of significance. The environmental impact due to irrigation showed level of significance extremely high.