Abstract
Sprinkler selection influences the water distribution uniformity of center pivot irrigation systems. The sprinkling uniformity of the center pivot is crucial for the yield and quality of crops on a large scale. Rotating and fixed spray plate sprinklers (RSPSs and FSPSs) are the two most popular types. However, sprinkler selection is mainly based on price, not on differences in performance between them. Under low-wind field conditions, the water distributions of individual RSPSs and FSPSs with different nozzles (2.78, 4.76, and 6.75 mm in diameter) were measured using a catch can method. Cubic spline interpolation was used for data conversion for FSPS measurements; the nozzle configuration model was used to simulate the water distribution of the same-nozzle-sprinkler pipe section and full circular irrigated areas in a simulated center pivot under three sprinkler intervals of 1.5, 3.0, and 4.5 m respectively. Results showed that (1) individual RSPSs distributed the most water around the sprinkler, whereas individual FSPSs distributed the most water over a ring-shaped region at the periphery of the sprinkler, and the wetted radii for RSPSs and FSPSs ranged from 4.88 to 7.05 m and from 5.02 to 6.85 m, respectively; (2) same-nozzle-sprinkler pipe sections of RSPSs distributed the most water around the central axes of the pipe sections, and their sprinkling uniformities were 44.7%–51.0%, whereas FSPSs distributed the most water over both sides of the axes symmetrically, and less water around the axes, with sprinkling uniformities of 40.3%–58.0%; and (3) the sprinkling uniformities of the full circular irrigated areas were 85.8%–91.7% and 85.8%–86.2% when using RSPSs and FSPSs, respectively, under different sprinkler intervals, and the uniformities were 3.1% and 6.2% higher using RSPSs than FSPSs with sprinkler intervals of 3.0 and 4.5 m, respectively. RSPS accommodated larger sprinkler intervals (>3.0 m) and maintained superior sprinkling performance when compared with FSPS.
Highlights
Since a major incident involving contaminated milk in China in 2008, the scale of planting of high-quality forage grass has increased rapidly, in which alfalfa (Medicago sativa L.) has been the major cultivar [1]
Results showed that (1) individual rotating spray plate sprinklers (RSPSs) distributed the most water around the sprinkler, whereas individual fixed spray plate sprinklers (FSPSs) distributed the most water over a ring-shaped region at the periphery of the sprinkler, and the wetted radii for RSPSs and FSPSs ranged from 4.88 to 7.05 m and from 5.02 to 6.85 m, respectively; (2) same-nozzle-sprinkler pipe sections of RSPSs distributed the most water around the central axes of the pipe sections, and their sprinkling uniformities were
Notes: RSPS, rotating spray plate sprinkler; FSPS, fixed spray plate sprinkler. These results suggested that the 3.0- and 4.5-m sprinkler intervals highlighted the advantages of RSPSs
Summary
Since a major incident involving contaminated milk in China in 2008, the scale of planting of high-quality forage grass has increased rapidly, in which alfalfa (Medicago sativa L.) has been the major cultivar [1]. In 2014, nationally, forage grass was cultivated in more than half a million hectares, of which alfalfa accounted for more than 80%, with the corresponding increasing land use and the need for irrigation globally [2,3,4]. Alfalfa consumes a lot of water during its growing season, usually around. Apart from the limited natural rainfall [6], high-efficiency irrigation is necessary [7]. With the evolution of water-lifting devices [8], the center pivot sprinkler irrigation system (center pivot) has been a popular irrigation method worldwide [9].
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