The Effect of Intermittent Addition on the Wetness Pattern of Subsurface Drip Irrigation

Abstract

The current study included 12 laboratory experiments on a soil model stacked inside a container with a metal structure with two transparent faces, in order to monitor the movement of the wetness front inside the soil with time; its dimensions are 50 cm, 50 cm, and 70 cm. The polka dot is fixed in one of its corners, sandwiched between the two transparent faces, to observe the quarter of the wet bulb formed in three dimensions. Experiments were carried out on two types of soil, mixture and clay, where the dripper works with two charges 130 cm and 105 cm above the dripper level. The processing is done in two ways: continuous (cycle ratio 1) and intermittent with a ratio of 1/2 cycle and a processing time of two hours for each cycle and a ratio of 1/3 cycle with a processing time of 1 hour for each cycle. The data that were monitored during the experiment period are the rate of drip discharge with time and the limits of the wetting bulb with time as well. Auto-CAD program was used for drawing the shapes of the progression of the wetness front with time from the obtained images, and these shapes were used for finding the distance of progress in the horizontal, vertical, upward and vertical downward directions for all twelve experiments. Microsoft-Excel program was used to estimate the distance of progress in the three directions in terms of the factors affecting them and with a coefficient of determination (0.902) for horizontal progression, (0.92) for vertical upward progress and (0.88) for vertical downward progress. The results showed that the droplet discharge changes with time by an exponential function, and that the rate of discharge increases at the beginning of each cycle and then returns to its true level after a period. The study also showed that the volume of wet soil because of processing a certain volume of water decreases as the cycle rate decreases.