The 2009 ASHS Annual Conference

Efficient water use and better irrigation control are increasingly important in ornamental production. Due to a lack of information about the water needs of plants, excessive irrigation is common. Excessive irrigation reduces profits because of unwanted leaching, runoff, power consumption, and labor. Lantana camara ‘Silver Mound’ and Abutilon x hybridum ‘Fairy Coral Red’ were grown from rooted cuttings in a greenhouse with 0.50 m³∙m^-3 volumetric substrate water content for 10 weeks. We used an automated irrigation system, which allowed control and quantification of daily water use (DWU), to quantify environmental effects on DWU of abutilon and lantana. Temperature, relative humidity, PPF, and daily light integral (DLI) were measured throughout the experiment. Daily maximum vapor pressure deficit (VPD_max) was calculated from the daily maximum temperature and the minimum relative humidity. The observed DWU ranged from 23 to 299 mL/plant for abutilon and from 32 to 315 mL/plant for lantana during the experiment. DWU was positively correlated with days after planting (DAP), DLI, and VPD_max. Using multiple regression analysis, DWU was described as a function of DAP, DAP², DAP×DLI, and VPD_max (R² = 0.95 and 0.94 for abutilon and lantana, respectively). Predictive models that describe the daily water needs of greenhouse crops can be used to make greenhouse irrigation more efficient, thereby reducing both the costs and environmental impact of greenhouse production.