Transformation of gray forest soils upon technogenic salinization and alkalization and subsequent rehabilitation in oil-producing regions of the southern Urals

The technogenically induced salinization and alkalization (solonetzization) of gray forest soils results in their transformation into soils similar to natural solonchaks and solonetzes. Their density increases, the structure is disturbed, and the water stability of the aggregates becomes poorer. The humus content decreases, the nutrition regime is deteriorated, and the enzymatic activity is hindered. Under natural conditions, soil desalinization is seen within a ten-year-long period after its contamination with strongly saline oil-field waste water, while soil solonetzization remains very high. The soil properties are regenerated after application of an adequate rate of phosphogypsum and manure. Phosphogypsum applied alone causes a deterioration of the agrophysical properties as it produces an extremely high water stability of aggregates and strong soil compaction.