Fitting a numerical model for the analysis of wet bulb dimensions by drip irrigation

Abstract

Drip irrigation is globally acknowledged as the most efficient system. However, the concept of "efficiency" relies on irrigation cultural practices, local agro-climatic conditions, and soil characteristics. In Uruguay, the absence of accurate wet bulb shape prediction often leads to common over-irrigation practices. Consequently, water loss through deep percolation, groundwater contamination, reduced crop yields, higher energy expenditure, and elevated fertilizer usage introduce uncertainties about the true efficiency of drip irrigation. The primary objective of this study is to develop a methodology for estimating wet bulb dimensions and their dynamics under drip irrigation. To achieve this, an experiment was conducted using a lysimeter containing representative soil from southern Uruguay. Alfalfa was irrigated using a central dripper with varying application times and flow rates. The lysimeter was equipped with tensiometers, and moisture observations were made with a neutron probe. The collected data were used to calibrate a numerical model implemented in the Code Bright program (UPC, Barcelona, Spain). The model exhibited a good fit in the upper strata (h<60cm), and revealed a deeper and thinner bulb compared to estimates found in the literature for soils of similar texture. This model, accurately computing the wet bulb's shape in heavy and stratified soils in Uruguay, allows simulations of various irrigation scenarios. Consequently, this work holds great potential for improving the efficiency of drip irrigation in the region.