Abstract
Due to restrictions and limitations on agricultural water worldwide, one of the most effective ways to conserve water in this sector is to reduce the water losses and improve irrigation uniformity. Nowadays, the low-pressure sprinkler has been widely used to replace the high-pressure impact sprinklers in lateral move sprinkler irrigation systems due to its low operating cost and high efficiency. However, the hazard of surface runoff represents the biggest obstacle for low-pressure sprinkler systems. Most researchers have used the pulsing technique to apply variable-rate irrigation to match the crop water needs within a normal application rate that does not produce runoff. This research introduces a variable pulsed irrigation algorithm (VPIA) based on an ON–OFF pulsing technique to conserve irrigation water through (1) decreasing the runoff losses by considering the soil infiltration rate, surface storage capacity, and sprinkler wetting diameter; and (2) ensuring a high level of water distribution uniformity in the direction of machine movement. From a wide range of pulse numbers and widths tested applying a certain water depth to a sandy loam soil, the best solution that gives the lowest runoff and highest uniformity while delivering an acceptable water depth was selected. A MATLAB code was written to simulate the soil infiltration rate, the sprinkler application rate, and to apply the proposed algorithm. The simulation results showed a runoff reduction of at least 90.7% with a high level of distribution uniformity in the direction of movement while delivering the highest possible irrigation depth using the lowest number of pulses.
Highlights
Many factors put pressure on freshwater resources, such as climate change, pollution, and population increase [1]
The code consists of four steps: In the first step, for each speed of the irrigation machine, the surface runoff potential will be checked according to the sprinkler ponded infiltration rate that corresponds to the application rate of the specified speed
The second step comprises the calculation of the runoff solution table (RST), which contains the best solutions of the number of pulses and the ON and OFF widths for the speeds at which the runoff exceeds the allowable threshold which is listed in the runoff potential table (RPT)
Summary
Many factors put pressure on freshwater resources, such as climate change (global warming), pollution, and population increase [1]. These pressures lead to an increase in the demand for fresh water, while the availability of it is decreasing [1]. Self-propelled sprinkler irrigation machines irrigated more than 12.5 million hectares worldwide [2], and they have become widely used to replace other conventional irrigation methods such as flood irrigation and some other types of sprinkler irrigation [2,3,4,5]. The application efficiency for the self-propelled sprinkler systems is the highest among all the other types of sprinkler systems, and applying water on a regular and Horticulturae 2019, 5, 10; doi:10.3390/horticulturae5010010 www.mdpi.com/journal/horticulturae
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