Forecasting Scanning Branches of the Hysteresis Soil Water-Retention Capacity for Calculation of Precise Irrigation Rates in Agricultural Landscapes Using a Mathematical Model

Abstract

A mathematical model of the hysteretic soil water-retention capacity is proposed. Based on this model, a computer program called «Hysteresis» was developed. This program has options for identifying model parameters by the method of dot-fitting of experimental data, as well as for performing predictive calculations and graphical representation of the branches of the hysteresis loop. A series of computational experiments was performed in which the possibility of identifying the parameters of the mathematical model from the data on the main (boundary) branches of soil drying and wetting was investigated, and the accuracy of the predictive calculations of the scanning branches of the hysteresis loop was estimated. Data from the literature on four soils are used. The model has been compared with three models of predecessors. A sufficiently high accuracy of forecasting the scanning branches has been achieved. The practical value of the proposed model is the possibility of calculating precise rates for crop irrigation. Application of such rates: (i) prevents the percolation of excess moisture from the root layer of the soil; (ii) minimizes the loss of irrigation water, fertilizers, ameliorants and plant protection products and (iii) reduces the risk for groundwater contamination with agrochemicals and the threat of water eutrophication.