Modelling Moisture Dynamics of Agricultural Steppe Soils in the Greater Caucasus
Turkan Hasanova1* 
, Gunay Mammadova2 ,
Mariam Tsitsiagi3 , and Normurod Lapitov4
Abstract. The aim of the work is to study the dynamics of moisture and the process of moisture infiltration in grey-brown ordinary plowed soil under conditions of natural moisture, after precipitation. The relevance of this research problem is also determined by the progressive degradation of the soil cover, its intensive exploitation, the deterioration of the water and nutrient regime of agricultural soils, erosion, desertification, and salinization. Accurate information on the water regime of steppe zone soils is crucial for maintaining their biological productivity. The modeling data correlates well with experimental data on changes in soil moisture, which will allow for future forecasts and hydromeliorative calculations. The main hydrological parameters of the soil (approximation parameters of the main hydrophysical characteristic) of the agricultural landscape soils were obtained using Rosetta Lite pedotransfer functions in the RETC program, using data on particle size distribution, density, porosity, minimum water capacity, wilting point, and yield point moisture content. It was found that the α parameter (the reciprocal of the capillary air entry pressure during soil drying) is significantly lower in the upper arable horizon than in the denser B and C horizons, which is typical for soils subject to tillage. Moisture chronoisopleths were constructed in the Surfer program, clearly reflecting changes in the moisture status of the soil horizons of the arable steppe during and after rainfall. It has been established that, as early as the third day after precipitation and with the initial moisture level in the upper arable horizon, the pressure in all soil layers equalizes. In the absence of a pressure gradient, the downward flow of moisture between horizons virtually ceases.
Keywords: capillary-sorption pressure, hydrological and hydrophysical characteristics, soil humidity, pedotransfer functions, modeling, vegetation