Caracterização dos problemas de sais dos solos irrigados do projeto São Gonçalo.

Abstract

The present work aimed to characterize the salt problems of the DNOCS São Gonçalo Irrigation Perimeter, in Souza-PB, aiming at the formulation of soil and water management standards. The studies carried out were of a general character salinity and conducted throughout the agricultural operation area of ​​the perimeter. In an area of ​​1,320 ha samples were taken, in 100m grid, the following depths: 0-30, 30-60, 60-90cm, totaling 3,960 samples. The physical and chemical analyzes were performed according to the methodology adopted in the EMBRAPA soil, water and forage laboratory in Petrolina-PE. On all samples The following determinations were performed: electrical conductivity of the saturation extract, pH, calcium, magnesium, sodium, potassium, hydrogen plus aluminum and exchangeable aluminum. For a group of well-defined saline, saline-sodium and sodic soil samples, grain size, hydraulic conductivity, sedimentation volume and moisture retention curve were determined. From the analysis of the obtained results it was concluded that: a) The São Gonçalo Irrigation Project presents sodic soils in 24% of the operating area, and soils saline sodium in 4% of the same area. b) An analysis of the sectoral situation of the Project indicated that: - Sectors 1, 2, 7, 8, 38, 42, 44 and 46 do not have no type of salt problems; - Sectors 3, 9, 17 and 37 present problems soluble salts and high percentage of exchangeable sodium (saline soils); - sectors 3, 4, 5, 6, 9, 11, 12, 13, 14, 16, 17, 20, 21, 22, 23, 24, 30, 31, 37, 39, 43 and 45 have percentages of exchangeable sodium greater than 15% (sodium soils); - Gypsum application needs in sodic soils vary between 9 and 2 9.3 tons per hectare.