The aim of research is the development of physico-mathematical models for calculating geometrical parameters of local contours of drip irrigation that consider the main hydrophysical soil characteristics. During research it was found that several (two, three or more) independent soil characteristics must be considered when developing physico-mathematical models for calculating both the geometrical and moisture parameters of moisture contours. The analysis of experimental data made it possible to identify the following basic soil characteristics that have the greatest impact on the formation of drip irrigation contours: the physical clay (particles smaller than 0.01 mm) in soil, the lowest soil moisture capacity, and the rate of soil water absorption for the first hour. The dependencies by V. N. Shkura and D. L. Obumakhov are known among the assumptions on geometric dimensions of moisture contours, considering soil characteristics quantitatively. In these dependencies soil conditions are considered by the amount of physical clay in soil. In the course of investigation a further processing of the experimental material obtained by V. N. Shkura and D. L. Obumakhov was carried out, as a result of which models for determining the geometric parameters of local moisture contours, taking into account the lowest moisture capacity of soil and absorption rate of soil for the first hour. The depth and diameter of local drip irrigation contours are proposed to be determined using the models that take into account each of the soil parameters examined, and the final value is taken as the average of the three parameters considered. Verification of the acceptability of the proposed models and dependencies is carried out by comparing the results of calculations on them with experimental data. As a result of research it was found that the proposed models allow to determine the linear dimensions of local contours of drip irrigation with an accuracy acceptable for practice (with an error not exceeding ±12 %) within the considered limits of the change in impact factors.
Key words: drip irrigation, local moisture contour, geometrical parameters of local contour, physical clay content in soil, the least moisture capacity of soil, water absorption rate by soil.
