Effects of Steady Intermittent Fertilizer Injection on Uniformity of Water and Fertilizer Mixture in Irrigation Pipe

Abstract

【Objective】 Intermittent fertilizer injection is commonly used in fertigation. The objective of this paper is to investigate the impact of steady intermittent fertilizer injection on the uniformity of water and fertilizer mixture within the head pipe in the irrigation network as well as the minimum safe distance for the branch pipes. 【Method】 Laboratory experiment was conducted to analyze the change in fertilizer concentration in the pipeline under ideal working conditions. The experimental results were used to validate a numerical model developed to simulate water flow and fertilizer movement in the pipe network. The validated numerical model was then used to evaluate the uniformity of water and fertilizer mixture in the pipe network under different conditions, including pipe diameter, water temperature, flow rates and fertilizer injection ratio. 【Result】 The numerical model accurately reproduced the experimental results. The modelling results showed that when other conditions were constant, increasing the main pipe diameter from 63 mm to 110 mm increased the mixing distance by 0.769 m. Increasing the main flow rate from 6 m3/h to 8 m3/h increased the effective mixing distance by 1.598 m, 1.064 m, and 1.132 m for pipe diameters of 63 mm, 90 mm, and 110 mm, respectively. When the fertilizer injection ratio was increased from 2% to 4%, the effective mixing distance was reduced by 0.534 m, 0.824 m, and 0.826 m for pipe diameters of 63 mm, 90 mm, and 110 mm, respectively. It was also found that increasing the temperature from 10 ℃ to 30 ℃, the effective mixing distance of 6 m3/h and 8 m3/h decreased by 0.499 m and 1.681 mm on average. 【Conclusion】 The effective mixing distance required for uniformizing water and fertilizer in the irrigation pipe increases with the pipe diameter and flow rate, and decreases with the increase in temperature and fertilizer injection ratio. Pipe diameter and flow rate are the primary factors influencing the effective mixing distance. For main pipes with diameters of 63 mm, 90 mm, and 110 mm, the opening position for branch pipes should be 5~5.5 m away from the fertilizer injection pipe to ensure uniform mixture.

Keywords

• water and fertilizer integration
• numerical simulation
• multiphase flow
• fertilizer injection tee pipe
• steady oscillating flow