Soil water distribution using subsurface string irrigation for water saving by negative pressure difference

抄録

Water-saving irrigation is important in arid areas because of water shortages and the need to prevent salt accumulation. Subsurface irrigation is one of the most effective methods of water conservation, as well as the irrigation method using the negative pressure difference. In this study, the water characteristics of the string, i.e., the main material of a string irrigation system, were measured in the water absorption processes. Nylon and cotton strings with diameters of 6 and 3 mm, respectively, were used. The pot experiment of the subsurface string irrigation via the negative pressure difference for water saving was conducted under three conditions: cotton (6 mm), cotton (3 mm), and nylon (3 mm). The conditions of the hydraulic head were 5 and 10 cm. Furthermore, a numerical simulation of soil water distribution was conducted using Hydrus-2D. As a result, 1) water characteristic curve of each string was obtained. Meanwhile, the water retention capacities of nylon (3 mm) and cotton (3 mm) were high of pF 0.5–1.5. 2) The effectiveness of string irrigation was confirmed. The maximum water supply was estimated as 91.6 g/d per pot on average string (cotton: 6 mm, hydraulic head: 10 cm). The average water supplies of cotton (6 mm), nylon (3 mm), and cotton (3 mm) were 33.7, 32.9, and 25.9 cm³/d, respectively. 3) Because the soil water distribution could be expressed through a numerical study, calculations corresponding to the arrangement of strings could be performed. These results will contribute to water conservation in arid area irrigation.