Influence of groundwater level fluctuation on meliorated salontz in the northern forest-steppe of the Baraba lowland

The purpose of the study: to determine groundwater level and chemistry and their influence on soil properties. Location and time of the study. Northern forest-steppe of the Baraba lowland (Chulymsky and Chanovsky districts of the Novosibirsk region, Russia), 2011–2021. Methods. Determination of the groundwater level and subsequent collecting groundwater samples from the temporary wells in the experimental areas (with chemical melioration by applying gypsum and agrobiological melioration by destroying the solonetz horizon and sawing salt-resistant crops). Under laboratory conditions, soil and groundwater chemical properties and the cation-anion composition of the water extract of soils were measured. Main results. Changes in the standing level of soils and their mineralization were revealed. The rise in the groundwater level resulted in the accumulation of easily soluble salts the soil profile, the saturation of the soil-absorbing complex with exchangeable sodium, and the restoration of the solonetzic horizon. In medium-deep and shallow solonetzes, reclaimed by the agrobiological method, the groundwater level was located at 240-250 cm in 2021, and salinization occurred only in the lower part of the profile (35-100 cm), while in the control variant, salinization occurred along the entire 1m profile. Conclusion. In most of the Baraba Lowland, the capillary fringe of groundwater is constantly or periodically present in a soil profile. Under conditions of increased moisture in the territory, the development of degradation processes, such as soil secondary salinization and solonetzization, is diagnosed. In chemically reclaimed crusty solonetzes, with periodical groundwater rise to the 50 cm depth, the ameliorative effect had been maintained for more than 30 years, after which there took place a gradual secondary salinization of the soil profile and the accumulation of exchangeable sodium in the soil absorbing complex. Over the last decade both meliorated areas saw the groundwater table rise, bringing soil secondary salinization and solonetzization. Chemical melioration proved its efficacy in not only improving soil properties, but in sustaining it under soil secondary salinization by groundwater. Agrobiological approach to solonetz melioration can also be considered perspective for slowing soil quality deterioration and sustaining soil fertility.