Determining the Irrigation Rate for Drip-Moistened Soil Primary Local Contour Formation

Abstract

Purpose: development of methodology for determining the irrigation rate value, which ensures the formation of a primary local contour of moistened soil in the soil space under drip irrigation with one emitter. Materials and methods. The methodological and factual basis of the development were materials and empirical dependencies obtained from the data of author's field studies of local moisture contours formed under various soil conditions with above-surface and surface drip irrigation. Results and discussion. The analysis and evaluation of known approaches to the calculation of irrigation rates for drip irrigation of plants is carried out, the direction of the development of the methodology is determined. Based on materials of field and office studies, 11 contour profiles of drip-moistened soil formed under various soil and technological conditions of drip irrigation were obtained. Soil conditions are characterized by a wide range of changes in their parameters: the content of physical clay is from 20.8 to 74.6 % of the dry soil mass (DSM), the lowest moisture capacity is from 16.9 to 32.2 % of DSM, the level of additional irrigation moisture is from 60 to 70 % of the lowest moisture capacity. Moisture contours were formed with an average soil moisture content of 90 % of the lowest moisture capacity. Empirical dependencies for determining the maximum and average radius (diameter) of moisture contours at given depths of the moistened soil layer, which make it possible to predict the volumes of moisture contours are obtained. The dependence and a method for calculating the irrigation rate value, which ensures the formation of a moisture contour of a given depth and a given level of soil moisture, are obtained for a wide range of granulometric and water-physical characteristics of soils. Conclusion. A method for calculating the irrigation rate required for the formation of a local moisture contour in soil space with specified dimensional and moisture parameters during irrigation water delivery by one drip micro emitter is proposed.