Developing a physiological-based, on-demand irrigation system for container production

A demand-based irrigation system was developed for Hibiscus rosa-sinensis ‘Cashmere Wind’ based on the relationship between photosynthesis and substrate moisture level (moisture response curve). An experiment was conducted to evaluate the premise that biomass would decrease only when substrate moisture levels caused a significant reduction in photosynthetic rate. Irrigation set points were based on the moisture response curve and corresponded to 49, 41, 30, and 22 m3 m−3 volumetric water content (89–61% container capacity). Gas exchange and leaf water potential were greater for plants in the three wettest irrigation treatments. Plants under these treatments used 1.4, 1.2, and 1.05 times more water during the experiment than plants in the driest treatment. Biomass metrics were generally unaffected by treatments or were greater for one or both intermediate treatments. This research demonstrates that a demand-based irrigation system with a physiological basis (predicated on the relationship between photosynthesis and substrate moisture potential) could be an effective biorational approach for scheduling irrigation and reducing water consumption in container-grown nursery crops.

► Developed a demand-based irrigation system that addressed scheduling and volume.
► Set points based on relationship between photosynthesis and substrate moisture.
► Production using the 30% VWC set point reduced water consumption by 27%.
► No biomass or quality penalty for irrigating based on 30% VWC set point.
► A physiological basis for scheduling irrigation can effectively conserve water.