Physical properties, soil-hydrological indices and water regime of leached chernozem under apple orchard on the experimental production farm OPKh Gorno-Altayskoe

Abstract

The water-physical properties, soil-hydrological parameters and the process of moisture movement in the leached chernozem under the apple orchard on the experimental production farm OPKh Gorno-Altayskoe under the conditions of a soil-reclamation (flooding) experiment were studied. Soil moisture was determined by the thermostatic-weight method; soil particle-size composition was determined by the pipette method according to N.A. Kachinskiy; soil density was determined by the cutting-ring method; the density of the solid phase was determined by pycnometry. The Van Genuchten function was used to restore the basic hydrophysical characteristics (WRC) of the soil; the parameters of WRC approximation were obtained using the pedotransfer functions “Rosetta Lite” using data on density and particle-size composition (the values were translated to the FAO international classification by the method of graphical interpolation). It was found that the upper well-structured A horizons of chernozem under the apple orchard had a greater water retention capacity, whereas the WRC of the B2c horizon which was the lightest in terms of granulometric composition, was significantly shifted towards lower moisture. Filtration coefficients in the leached chernozem under the apple orchard varied from 30.5 cm per day in Ad horizon and to 6 cm per day in the lower horizon. The moisture deficit in the soil during the hot and dry weather of June 2023 was 14 mm in the upper 20 cm of soil depth. The HYDRUS-1D software simulated the changes of moisture storage in soil horizons after precipitation. It is shown that the rapid downward penetration of moisture into the lower horizons is prevented by the clay layers and the absence of a proper pressure gradient. The upward moisture flows have a significant effect on the distribution of water in the leached chernozem under the apple orchard during the dry period. The model shows the smallest discrepancies between the calculated and measured moisture values a day after the start of the experiment. The model adjustment based the experimental data enables its use to predict further processes of moisture distribution in the soil.