Use of agricultural gypsum in the recovery of salinized soils in the brazilian semiarid region

Abstract

The excessive exploitation of natural resources has led to various problems, including the formation of saline soils. To continue using these soils, corrective techniques are necessary. A promising approach is the application of agricultural gypsum (CaSO₄⋅2H₂O), which acts as a source of calcium (Ca²⁺) in the recovery of soils degraded by salts. Thus, this study aimed to utilize gypsum for soil recovery in a semiarid area affected by salt degradation and determine the number of washes required for salt leaching. Soil samples were collected in the municipality of Sumé and analyzed at the Soil Laboratory of the Center for Sustainable Development in the Semiarid (CDSA). The experimental design used was a Completely Randomized Design (CRD) with five gypsum application rates (0, 2.5, 5, 7.5, and 10 g). After application, the soil was hydrated to field capacity (FC). Two washes were performed to leach the salts: the first with 637 mL (3.5 times FC) and the second with 273 mL of distilled water (1.5 times FC). The addition of gypsum favored salt leaching, with Na⁺ concentrations approximately 4.8 times higher in the first wash compared to the second. Correlation analysis indicated that gypsum had a negative interaction with Na+ ion leaching in the second wash, suggesting that most of these ions were already leached in the first wash. Therefore, it is concluded that CaSO₄⋅2H₂O is recommended for treating saline soils. The leached Na⁺ values do not justify a second wash, considering the potential loss of other ions, such as K⁺.