STRUCTURE FORMATION OF MOISTURE EXCHANGE IN THE AERATION ZONE OF AN IRRIGATED FIELD IN PRESENCE OF A CAPILLARY FRINGE IN SOIL THICKNESS

Purpose: scientific and technical substantiation of water balance components of an irrigated field in the particular case of the connection of an aquifer and aeration zone through a capillary fringe. Materials and methods. The studies were carried out in Pobeda LLC, Bagaevsky district, Elkin farm in 2018 and 2019. When organizing studies, an integrated approach was used: stationary and experimental plots were used. The climatic conditions of the research objects correspond to the semi-arid steppe zone, the soils are southern chernozems. Results. As a result of processing the field experience data, it was determined that for the conditions of an average dry year in the last third of May, the water table occurrence, calculated according to the radiation balance, is at a depth of 1.0 m, the average daily water consumption is 6.5 mm, groundwater feeding – 2.9 mm, and at a depth of 1.5 and 2.0 m – 2.0 and 1.25 mm, respectively. For the conditions of an average year in the phase of the beginning of alfalfa flowering (in the first days of June), the average daily water consumption is 5 mm, and groundwater recharge is 2.2; 1.38 and 0.81 mm at a depth of groundwater level of 1.0; 1.5 and 2.0 m respectively. The values of water consumption are obtained from the heat balance equation of the active surface, the dynamics of moisture exchange elements in the aeration zone of an irrigated alfalfa field, a comparative assessment of the evaporation obtained by the following methods is given: radiation balance (accuracy 0.89), N. N. Ivanov (accuracy 0.68) and the modified model of S. I. Kharchenko (accuracy 0.88), with the corresponding mathematical processing (coefficient of variation, dispersion, deviation) by the sum of accumulated effective temperatures compared with the actual data. Conclusions: as a reference method, the method of determining the evapotranspiration of agricultural crops according to the radiation balance should be used; the implementation of the required model according to S. I. Kharchenko makes it possible to increase the accuracy of determining the desired value by 30 % compared to the determination model according to N. N. Ivanov.