Irrigation application efficiency calculation of sprinkler irrigated container plants grown under sensor based irrigation scheduling

Outdoor studies were conducted to evaluate water application efficiency (WAE) between two irrigation scheduling methods. Buxus × 'Green Velvet' plants were grown in 3.7-L containers using overhead sprinkler irrigation. Plants were irrigated to near container capacity either on daily basis or when a physiologically based set point (0.28 cm3 cm-3 volumetric water content) was reached. Irrigation efficiency of overhead irrigation can be characterized using water use efficiency (WUE), calculated as total dry weight divided by total water volume applied, including precipitation. Even though there was no difference in dry matter production between the irrigation methods, significant water savings existed when irrigation was based on a set point. WAE was calculated by a new method using sensor-based substrate volumetric moisture content (SVMC) values. The volume of irrigation water stored in the root zone was calculated by deducting the SVMC values before irrigation from SVMC one hour after irrigation and that difference was divided by the volume of water delivered to the container, which was calculated as the difference between container capacity and SVMC before irrigation. Set point-based irrigation showed higher WAE than daily water use-based irrigation scheduling. Increased pre-irrigation substrate moisture deficit has been attributed to high WAE of set point-based system.