Assessment of water-physical properties of soil for the cultivation of pomegranate varieties in dry subtropics

Abstract. The purpose of the research was to study the water regime of meadow chestnut soil in the conditions of Southern Dagestan in connection with the use for pomegranate plantations. Generally accepted methods were used for studying the soil of the experimental sites: the morphological description of the soil was carried out according to Golubev I.F.; the structural composition – according to N.I. Savinov; the mechanical composition – by the method of N.A. Kachinskiy; the soil density – by the device of N.A. Kachinskiy; the specific gravity – by the technometric method; the lowest moisture capacity of the soil – by flooding the area according to N.A. Kachinskiy; the permanent wilting point – by the method of seedlings according to S.I. Dolgov in natural conditions, i.e. directly on pomegranate plantations; the maximum hygroscopic moisture – according to the method of A.V. Nikolaev; the moisture content at capiillary rupture was calculated according to the method of S.I. Dolgov; the soil filtration – according to the method of N.A. Kachinskiy. For the first time, the permanent wilting point threshold of the pomegranate plant (8.5 %) was established and the ability of the pomegranate plant to assimilate the maximum hygroscopic moisture of the soil was revealed. It has been established that the regulation of the water regime of the soil is the main link on which the efficiency of other factors depends. In arid areas, the use of fertilizers and machinery, without improving the water regime, cannot ensure a high yield. The assessment of the optimality of soil conditions and limiting factors in the cultivation of introduced pomegranate varieties showed that the specific gravity of the soil, depending on the depth of sampling, is 2.6-2.72 g/cm3 , the soil density is 1.26-1.31 g/cm3 , the absolute moisture content is 14.1-25.0 %, the porosity is 41.2-57.2 %, the physical sand is 52.4-60.6 %, the physical clay is 39.4-47.6 %, the lowest moisture capacity is 20.6-26.2 %, and the permanent wilting point is 11.4-17.9 %. Positive correlations were obtained between the depth of soil sampling on the one hand and the specific gravity of soil particles (r = 0.53), the soil density (r = 0.65), the absolute soil moisture (r = 0.93), the porosity (r = 0.90), the physical sand (r = 0.94), the physical clay in the soil (r = 0.95), the lowest moisture capacity (r = 0.97), and the permanent wilting point (r = 0.90). In the irrigated conditions of the dry subtropics of Southern Dagestan, characterized by aridity, the exchange of heat and light to obtain annual guaranteed yields of high-quality fruits of introduced pomegranate varieties, the optimal irrigation regime is 80 % of the FMC. Keywords: Southern Dagestan, dry subtropics, water regime, pomegranate culture, limiting factors, correlation coefficient