Irrigation/fertilization model and comprehensive evaluation system for a hose-reel sprinkler

A hose-reel sprinkler irrigation machine has been gradually applied for the field crop fertigation in recent years, particularly for the high-standard farmland construction. However, it is still lacking on the reasonable working parameters of the machine, leading to the high operating costs, low irrigation quality, and non-uniform fertilization. In this study, a calculation model of irrigation and fertilization was established to construct a comprehensive evaluation system for a hose-reel sprinkler irrigation machine. The working parameters were optimized to reduce the operating costs for the high quality of irrigation and fertilization. An indoor test was carried out on the typical low-pressure sprinklers, including the PG224 and PG134 sprinklers, as well as the Super Spray sprinkler (Senninger Irrigation, Inc., USA). A systematic analysis was made to obtain the flow rates, radius of throw, and radial water distributions of three low-pressure sprinklers. The results showed that the flow rate of sprinkler increased gradually, as the working pressure increased. Among them, the PG224 and PG134 sprinklers presented the higher degrees of atomization, where the water droplets were mostly concentrated within 0-2 m from the sprinkler. By contrast, there was the lower atomization degree in Super Spray sprinkler. The water droplets were mainly distributed in 4-5 m from the sprinkler, with the maximum water application rate of about 52.6 mm/h. A calculation model was selected to design the irrigation parameters, according to the available parameters of field plot, crop, soil, sprinkler, and irrigation machine. Fertilization parameters were also selected to apply in a piston injection pump. Five indicators were utilized for the evaluation system, including the sprinkler uniformity coefficient, designed water application rate, irrigation area, investment annual investment per unit area, and annual operating cost. Subsequently, a design software was developed to optimize the parameters of the machine, the irrigation, and fertilization using Web platform. A case study was the JP75-300 hose-reel sprinkler irrigation machine that applied for the winter wheat production in Beijing, China. There were the multiple low-pressure sprinklers at the spacing of 2.6 m on a truss with the length of 26 m, and a DC motor to drag the sprinkler cart. 12 configuration schemes with three low-pressure sprinklers were selected out after the comprehensive evaluation by principal component analysis (PCA). Specifically, the optimal scheme was the sprinkler type of PG134, with the working pressure of 0.15 MPa, and the corresponding sprinkler uniformity coefficient of 88.96%, the designed water application rate of 57.31 mm/h, the irrigation area of 5.05 hm2, the annual investment per unit area of 1 981.04 yuan/hm2, and the annual operating cost of 1 019.99 yuan/hm2. The finding can provide the technical support for the selection and parameter design of sprinkler irrigation machine in the irrigation and fertilization.