The non-judicious use of water at the farm level in traditional irrigation application methods is a present-day concern across the world that can be resolved by enhancing application efficiency through the adoption of advanced irrigation techniques. Sprinkler irrigation is a method that has high application efficiency, which can be further increased when coupled with automation toward precision irrigation. The objectives of this review are to summarize the main aspects of sprinkler and precision irrigation and their development, scope, and future prospects specifically in Asian countries. In this paper, a modified methodology, inspired by PRISMA guidelines, was used to explore the available literature to summarize the existing knowledge in the field. Regarding the technological aspects of the analyzed works, it became evident that sprinkler systems are an efficient method to not only irrigate crops (with 39% water saving) but also for the application of fertilizers with higher efficiency (>35%) and water productivity (>14.1%) compared with gravity irrigation systems. Moreover, this paper highlights the prominent features of precision irrigation for maximizing agricultural productivity. The use of sprinkler irrigation with precision applications using automation with a sensor-based mechanism for field data collection, data transformation, data analysis, and operation of IoT-based automatic solenoid valves can save 20–30% more irrigation water and increase crop yield by 20–27%. An analytical understanding and knowledge of the field were used to draw conclusions that are thought-provoking for scientists, researchers, and other stakeholders.

The integration of Internet-of-Things technology with traditional agricultural irrigation is a crucial factor in the advancement of traditional agricultural irrigation towards smart irrigation. Despite the widespread use of conventional irrigation methods in many areas, they lead to the significant wastage of both human and water resources. Therefore, the development of energy-saving and efficient intelligent irrigation systems through the application of Internet-of-Things technology and wireless communication technology is the way forward. This paper summarizes the common wireless communication technologies in the agricultural Internet of Things: Fifth-generation, WiFi, ZigBee, LoRa, and NB-IoT. The research status of the above wireless communication technology in agricultural irrigation management is discussed, and the agricultural irrigation management example using the above wireless communication technology is also presented. The advantages and limitations of the application of the above wireless communication technology in agricultural irrigation management are sorted out. Finally, this paper analyzes the challenges of data security issues, data fusion problems, intelligent irrigation system costs, power and energy problems, and system equipment failures faced by the use of IoT wireless communication technology in agricultural irrigation management. This review aims to assist researchers and users in choosing the most suitable wireless communication technology for diverse applications.

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.

Using low-pressure sprinklers in agricultural irrigation has become an alternative way of reducing water and energy stress. To determine the applicability of the low-pressure rotating sprinkler, an experiment was conducted to evaluate the effects of working pressure and nozzle size on sprinkler rotation speed, application rate, droplet size, droplet velocity, droplet trajectory angle, and kinetic energy distribution. The results showed that the mean droplet diameter increased exponentially along with the increase in distance from the sprinkler, and a logarithmic relation was derived between droplet diameter and droplet velocity. Due to the low breakup degree of the jet under the lowest working pressure of 100 kPa, the peak values of specific power and application rate were high, which reached 0.09 W m⁻² and 11.35 mm h⁻¹, and were 3.1–5.4 times and 2.5–3.1 times those of other working conditions. Meanwhile, the peak specific power of the biggest nozzle (diameter = 5.2 mm) was 2.4–2.8 times that of smaller nozzles. With an increase in working pressure, the sprinkler time per rotation decreased and the distributions of kinetic energy and water became more uniform. Thus, it is not recommended to equip the sprinkler with a large nozzle under low working pressure.

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.