2022 Volume 32 Issue 3 Pages 89
Water saving irrigation is important in arid area because of the water shortage and the prevention of salt accumulation. Subsurface irrigation is one of the most effective method of water saving, and the irrigation method by the negative pressure difference is also effective. In this study, the water characteristics of the string which is the main material of the string irrigation system were measured in the water absorption and drainage process. As the type of string, Nylon, Cotton and Cremona (60% vinylon and 40% polyester) which diameter of 6 mm and 3 mm were used. The pot experiment of the subsurface string irrigation by the negative pressure difference for water saving was conducted under three conditions of Cotton (6 mm), Cotton (3 mm) and Nylon (3 mm). The condition of hydraulic head from groundwater was 5 cm and 10 cm. Further, the numerical simulation of soil water distribution using Hydras 2D was conducted. As the results, 1) Water characteristic curve of each string were obtained. The water retention capacity of Cotton (6 mm) was the highest in all potential ranges in the drainage process. The water retention capacity of Nylon (3 mm) and Cotton (3 mm) were high from pF 0.5 to pF 1.5 in the water absorption process. 2) The maximum water supply was 79 g/day per pot on average at the condition of the cotton string (ϕ: 6 mm, hydraulic head:10 cm). The minimum water supply was 34 g/day per pot on average at the condition of cotton string (ϕ: 3 mm, hydraulic head:10 cm). 3) Since the soil water distribution could be expressed by the numerical study, the calculations corresponding to the shape and arrangement of strings could be performed. These results will contribute to save water in arid area irrigation.
