Growth Response of Date Palm (Phoenix dactylifera), Royal Palm (Roystonea regia), and Washington Palm (Washingtonia robusta) to Saline Irrigation Water

With increasing population demands on the world’s water supply, there is a greater need for water conservation. Thus, nursery producers are challenged to avoid the use of high-quality potable water for irrigation. In arid and semiarid climates where water is limited, soil salinity is major problem and palm production can be challenging. The objective of this study was to evaluate the impact of different levels of salinity on the growth of date palm, royal palm, and Mexican fan palm. Palm liners were grown in 1-gallon containers in the greenhouse located at the University of Florida, Fort Lauderdale Research and Education Center, Davie, FL. Palms were irrigated with water having five different salt concentrations:  0, 5, 10, 15, and 20dS/m). Palms were fertilized with controlled- release fertilizer (Osmocote Plus, 15N- 9P₂O-12K₂O, 12-14 months@ 70^◦F). A supplement of calcium sulfate was added as liquid (drench) and magnesium was added as granular kieserite (surface application). Plants were watered with salt solutions by hand at a rate of 250 ml three times a week. Measurement of growth was taken monthly, height for each plant was measured to the tip of the tallest fully extended leaf, and number of new mature leaves per plant was counted.  Mexican fan palms started to show mild injury symptoms in all EC levels (0, 5, 10, 15, and 20 dS/m) by week 6, then severe injury symptoms started showing after week 8. Royal palms showed severe symptoms at the highest EC level (10, 15 and 20 dS/m) after 8 weeks compared to other EC levels where the injury symptoms were moderate. Date palms showed the most tolerance to salinity up to 12 weeks under all treatments and after that these plants began to show mild symptoms (leaflet tip necrosis) at the highest two EC levels (15 and 20 dS/m). With increasing the EC levels, all three species showed reduced growth