Eletroquímica e movimentação de íons em solos arenosos com lamelas do Agreste de Pernambuco

Abstract

Regolithic Neosols often present different productive potential associated with lamellae occurrence. Lamellae is a term attributed to the accumulation range of fine granulometric constituents in sandy sediments, clays and, or humic substances. With the accumulation of these materials all the electrochemical attributes of the soil can be altered, modifying the productive capacity of these soils. In view of the above, the objective of this work was to quantify and qualify the electrochemical attributes of sandy soils with lamellae from a topssequence of the Agreste of Pernambuco, as well as to observe the influence of these attributes on the movement of ions through the application of gypsum. For this, 3 profiles (P1, P2 and P3) marked by the occurrence of lamellae, and a profile without lamellae (P4) were selected in a topossequence in the city of São João, Pernambuco. In P1, P2 and P3 the electrochemical characterization was performed and P1, P3 and P4, the influence of lamellae on Ca2+ and SO42- ions was evaluated by the application of gypsum doses in microparcels of 2 m2. The experimental design was a randomized complete block design, with the treatments composed of gypsum doses defined by gypsum requirements (NG), that is, by installing microparcels of 2 m2 and applying five levels of gypsum in four replications: 50%, 100%, 150% and 200% of NG, randomly distributed in the blocks in four replicates. At 30, 60 and 90 days after the application of gypsum were collected by soil samples At depths of 0-20 cm and 20-40 cm, and at 90 days, the lamellae and interlayers were collected for the determination of Ca2+ and SO42-. The data were submitted to descriptive statistical analysis, linear correlation analysis for the comparison of the electrochemical variables, multivariate analysis and regression analysis to evaluate the variables as a function of the added gypsum doses. Based on the electrochemical characterization, the PCZ of the lamellas and interlayers were inferior to those found in the 0-20 layer in all profiles. The PESN of the lamella presented values between 8.4 and 2.8. The lamellae were responsible for generating electrical potential and predominantly negative liquid charge. The increase of negative charges by the lamellae produced higher CTC than that observed in the 0-20 layer in all profiles. The study of the interference of the lamellas in the movement of ions along the profiles showed that they functioned to retard Ca2+ movement after the treatments with gypsum.