Investigation of drip irrigation techniques

Abstract: The shortage of accessible water in the world is especially severe in arid regions, where many are already living to the limits of survival. In such areas, the conditions are in fact getting more extreme due to climate change and a growing population. The share of water is to be distributed for human use, as well as agriculture, which is why irrigation with lower quality water is essential. In addition, the soil in drought affected regions is often naturally saline, which makes it even harder to cultivate the land. The aim of this thesis was to study the infiltration pattern and salt leaching properties of three different irrigation methods. The experiments were conducted using a tube with an emitter connected to a submerged pump. The irrigation methods were; surface-, subsurface- and surface-covered-irrigation. For subsurface-irrigation the emitter was buried and for covered irrigation a transparent plastic sheet was used with the aim of preventing evaporation. The same volume and discharge of water were used for all methods, but were applied either during one day or dispersed over three. To be able to collect the data needed, a tracer was added to the experiment water before being applied to the soil, which was later excavated and photographed at regular intervals to note the water distribution. On the same levels the salinity were measured. For this a WET-sensor was used and soil samples taken for soil extraction in the laboratory. Several conclusions regarding the percolation could be made after analyzing the data. The results showed that, for all irrigation methods, the water infiltrated deeper and narrower when irrigating during one occasion. When comparing the different volumes of dye-affected soil, an unexpected result was shown; for all scenarios using surface covered irrigation the infiltrated water had a smaller volume than without a plastic cover. This may have been due to a green-house effect occurring under the transparent plastic sheet. However, the method that resulted in the largest volume of colored sand was subsurface irrigation, indicating that this method is better for preventing evaporation. The results for analyzing the leaching of salts were found to be poor. The WET- sensor proved to be an improper tool for measuring the salinity in loamy sand since the moisture was too low to give relevant readings