Efeito da frequência de irrigação sobre a lixiviação de nitratos em três solos do Estado da Paraíba.

Abstract

The present work had as objective, to study the effect of the frequency of irrigation under the leaching of nitrates in three soils of the State of Paraíba. The experiment was conducted at the Science and Technology Center of the Federal University of Paraíba and the soils studied were obtained from the Sumé, Arcoverde and São Gonçalo irrigation and colonization projects, all from the 3rd Regional Directorate of the National Department of Works Against (DNOCS). To determine nitrate leaching, columns of unaltered soil of 20 cm in diameter and 100 cm in length were used. The nitrate contents of soil and drainage samples were periodically analyzed. The analysis of the results allows us to observe that, for the soil from the Irrigation Perimeter Engineer Arcoverde (treatment II), the largest nitrate leaching corresponded to undertreatment II B (application of 4 cm of water every 7 days). This undertreatment showed the highest average water content (o) during the experiment. The evaporation of water, on the soil surface, delayed the nitrate leaching, due to the reduction of the available water content to be percolated and to a probable upward movement of nitrate in the soil. Analyzes of NO3-N leaching from the soil, of the São Gonçalo Irrigation Project (treatment III), showed that the highest leaching was evidenced in the undertreatments that presented the highest average water content (0), confirming the conclusions established for the treatment II. The results of the leaching and the nitrate balance, obtained with the different frequencies of Treatment Irrigation II, indicated remote possibilities of contamination of groundwater.