Abstract:     This study examined the effect of different negative pressures and soil textures on water and salt movement to improve the efficiency of negative pressure irrigation (NPI). Four soil textures of varying fineness (Loamy Sand, Loam, Silty Loam, and Sandy Loam) and three negative pressure values (0, –5, and –10 kPa) were used. As irrigation time increased, wetting front movement speeds decreased, and as negative pressure increased, wetting front size decreased. Coarse soils had the smallest wetting front under greater negative pressure. Next, water infiltration rate decreased as irrigation time increased, and coarse soils had the lowest average infiltration rate under greater negative pressure. Finally, salt content increased with distance from the irrigation emitter and with increased negative pressure. Further, coarse soils were found to have decreased desalination under greater negative pressure. Thus, soil texture has a strong effect on NPI efficiency. However, by adjusting pressure values in accordance with soil texture, soil water content can be controlled and maintained. These findings are important to the improvement of NPI systems, increasing their practicality for agricultural use.

Key words: negative pressure irrigation ,  volumetric water content ,  soil salt content ,  soil texture