IMPROVING APPROACHES TO CALCULATING LEACHING REQUIREMENTS FOR THE DESALINATION OF IRRIGATED SOILS

The relevance of this study for the Republic of Uzbekistan lies in the need for a modern approach to calculating leaching rates. This is due to: a decrease in water resources, currently and in the future; significant (more than 40% of the territory) spread of salinization on irrigated lands; changes in soil salinization types during long-term irrigation; the transition from the practice of surveying saline soils to a method of assessing the degree of soil salinity by electrical conductivity, which is widely used in world practice. Objective: Scientific and experimental substantiation of the application (adaptation) of the domestic formula of E.A. Nerozin for calculating leaching rates using the assessment of saline lands according to the FAO classification by electrical conductivity. Materials and methods: a database of experimental studies on leaching of saline soils and the substantiation of leaching rates, statistical data processing, empirical equations, clarification of salt removal coefficients. Results. Based on a study conducted in the previous period, which compared calculated leaching norms with actual norms from experimental leaching trials, and taking into account the authors’ new research on testing the FAO model, the validity of using A.E. Nerozin’s formula to determine the required volume of water for leaching saline soils has been confirmed. This formula initially takes into account the intensity of chlorine ion leaching from the soil. Using data (from the laboratory’s archives) on the results of experimental leaching, and previously established patterns of salt leaching from the soil, A.E. Nerozin’s formula has been adapted to the modern international classification for assessing soil salinisation according to the EC scale, which is already widely used in Uzbekistan when surveying irrigated soils for salinisation. The transition to assessing salt leaching according to EC in the formula was achieved using two methods: 1. by converting the chlorine leaching coefficient KCl in A.E. Nerozin’s table to a coefficient accounting for the decrease in ECe (KEC); 2. by applying the empirical equation for specific water consumption to reduce soil salinity by 1 dS/m. The domestic model of A.E. Nerozin for calculating leaching norms, which is as close as possible to the FAO model, is adapted to the international classification of soil salinity assessment according to the EC.