Modeling the effect of fertilizers on the dynamics of moisture contours at drip irrigation

Introduction. A review of research on modeling and calculating moisture contours shows that at this stage there is a developed formalized mathematical apparatus connecting physically reasonable parameters and hydro-physical properties of soils. However, to improve the efficiency of drip irrigation and fertigation, it is necessary to determine the effect of fertilizers dissolved in irrigation water on hydrophysic properties of soil, and on the basis of the findings to determine the effect of fertilizers on shapes and sizes of moisture contours. Materials and Methods. To investigate the effect of fertilizers on the dynamics of moisture contours, potassium monophosphate was used, because it has a “bad” mobility in soil and it is cost-efficient to be introduced into irrigation water. Potassium monophosphate effects on density, viscosity, osmotic pressure, moisture contact angle and surface tension of irrigation water. As a result, there are changes in soil water retention curve and its hydraulic conductivity function. Therefore, moisture contours are formed with small, but still significant differences. Results. A software tool has been developed that allows exploring the dynamics of the moisture contours of different soil types and texture with different porosity and with a previously known moisture distribution in depth. Discussion and Сonclusion. When potassium monophosphate or other nutrients are added to water, small changes of the formation of moisture contours are observed. The results obtained enable us to calculate irrigation norms at the design stage of the planning process of fertilizer distribution with irrigation water during drip irrigation for different concentrations.