Water saving is an essential part of sprinkler irrigation owing to the impact of climate change and rising energy costs. This review highlights the technologies that are emerging in sprinkler irrigation to optimize crop production. While there have been notable advances in irrigation, the continued progress has occurred by the combination of current status with the postulation of new ideas such as conversion of high-pressure sprinkler to low-pressure ones, incorporation of smart controllers in sprinkler irrigation systems. To enhance the adoption of these technologies, research on the dispersion device is needed to improve the performance of impact sprinklers to efficiently operate at low-pressure conditions. It is also important to study how water savings estimates based on water use, irrigated area, longevity of saving, and level of wasteful irrigation prior to the retrofit obtained from field trials can be extrapolated to other areas with different conditions. Research in the development of optimized method for irrigation scheduling is necessary. This review emphasizes that the status of technologies should be considered a continuum, building on earlier knowledge and progress, and hopefully leading toward optimized crop production in sprinkler irrigated areas. Keywords: sprinkler irrigation technologies, smart controllers, crop water demand, crop production DOI: 10.25165/j.ijabe.20191203.4310 Citation: Li H, Issaka Z, Jiang Y, Tang P, Chen C. Overview of emerging technologies in sprinkler irrigation to optimize crop production. Int J Agric & Biol Eng, 2019; 12(3): 1–9.

The pressurized irrigation network aims to deliver water to consumption nodes at an appropriate pressure and discharge. The traditional pipe network optimization minimizes the annual operating cost or investment per unit area. The present work establishes the traditional pipe diameter and operating frequency optimization models based on flattish terrain. It proposes a new synchronization optimization method of pipe diameter and operation frequency to find the best match point for pipe diameter and operating frequency in the branched network system. The irrigation costs of the above three models, including the energy and pipe network costs, are compared with the original irrigation network system. Based on the results of optimizing the typical experimental field, the operation frequency optimization model and the pipe diameter optimization model can save about 1.4% and 10.6% in irrigation cost, respectively. Furthermore, the synchronous optimization model can significantly reduce the irrigation cost to about 19.3%, including a 26.6% reduction in the pipe network cost and a 21.9% increase in the energy cost. Compared with pipe diameter optimization, synchronous optimization can further reduce network costs while generating lower energy costs. The results of this research can be used for the design of the network system in flattish terrain to reduce the irrigation cost.

To overcome the problem of poor uniformity of solid-fertilizer-dissolving devices due to lag of fertilizer dissolution, a closed-loop control system based on fuzzy proportional-integral-derivative (PID) was designed and tested. A fertilizer concentration regulation model was then established according to the results. In this system, the control core was an STM32 used to feed back the fertilization concentration by detecting the electrical conductivity. For real-time adjustment of the fertilizer flow rate and water flow rate, a fuzzy PID control algorithm was utilized to compare the detected concentrations with the set concentrations. The linear relationships between quantities such as the fertilizer rate and PWM frequency, water flow rate and PWM duty ratio of the direct-current pump, and fertilizer concentration and electrical conductivity were all established to calibrate the system. The influence of the fertilizer flow rate and water flow rate on fertilizer concentration was determined by the control variable test method. The results showed a positive linear relationship between fertilizer concentration and fertilizer flow rate, while a reverse linear relationship was established between fertilizer concentration and water flow rate. After the introduction of the control system into the self-developed solid-fertilizer-dissolving device, the fertilizer concentration fluctuated near the set concentration in a range of no more than 1 g/L. After the disturbance of the fertilization device, the control system fine-tuned the device with a steady-state error of about 0.55 g/L after the system reached stability. The control system designed in this study was shown to run normally with good stability, speed, and accuracy, and with improved fertilization uniformity of the solid-fertilizer-dissolving device. This study lays the foundation for further study of fertilization control systems. It also provides a reference for the development of precise and intelligent fertigation.

To solve the problem of non-destructive crop water content of detection under outdoor conditions, we propose a method to predict lettuce canopy water content by collecting outdoor hyperspectral images of potted lettuce plants and combining spectral analysis techniques and model training methods. Firstly, background noise was removed by correlation segmentation, proposed in this paper, whereby light intensity correction is performed on the segmented lettuce canopy images. We then chose the first derivative combined with mean centering (MC) to preprocess the raw spectral data. Hereafter, feature bands were screened by a combination of Monte Carlo uninformative variable elimination (MCUVE) and competitive adaptive reweighting sampling (CARS) to eliminate redundant information. Finally, a lettuce canopy moisture prediction model was constructed by combining partial least squares (PLS). The correlation coefficient between model predicted and measured values was used as the main model performance evaluation index, and the modeling set correlation coefficient R_c was 82.71%, while the prediction set correlation coefficient R_P was 84.67%. The water content of each lettuce canopy pixel was calculated by the constructed model, and the visualized lettuce water distribution map was generated by pseudo-color image processing, which finally revealed a visualization of the water content of the lettuce canopy leaves under outdoor conditions. This study extends the hyperspectral image prediction possibilities of lettuce canopy water content under outdoor conditions.

Hydraulic performance characteristics of impact sprinkler with a fixed water dispersion device

Jet breakup length is an important parameter which reflects the length of sprinkler range. Based on the linear instability theory, the dispersion equation of cylindrical jet was established and the theoretical value of jet breakup length was calculated. The jet breakup length and initial amplitude of surface wave were measured by applying the high-speed photography technology. Meanwhile, the numerical simulation was conducted by combining Level Set-VOF method for describing the jet breakup length to verify the theoretical and experimental results. Within the jet velocity and working pressure range of discussion, the results of comparison showed that the theoretical analysis gave a reasonable explanation to the influence of jet velocity, nozzle diameter and nozzle cone angle on jet breakup length. Comparing the theoretical value of jet breakup length with the experimental and simulated values, the three results accorded one another. The experimental jet breakup lengths were the lowest and the simulation values were the largest, and the relative error was less than 10%, especially the theoretical value was closer to the average value. For choosing the theoretical calculation of jet breakup length, a semi-empirical and semi-theoretical formula of range for the rotating sprinkler was concluded by the curve fitting method and the fitting formula was verified. The results showed the high accuracy of the ranges determined by this formula and the average relative error was less than 2.5%. The new formula was in good agreement with the data of different types of sprinklers comparing with other empirical formulas, and the error was only 5%. Meanwhile, the possibility of using this formula widely to determine the ranges of same series of sprinkler was confirmed. Keywords: sprinkler, irrigation, formula, cylindrical jet, jet breakup length, dispersion equation, high speed photography, Level Set-VOF method DOI: 10.25165/j.ijabe.20181101.2777 Citation: Jiang Y, Li H, Chen C, Xiang Q J. Calculation and verification of formula for the range of sprinklers based on jet breakup length. Int J Agric & Biol Eng, 2018; 11(1): 49–57.