Impact of Water Treatment on Foliar Damage of Landscape Trees Sprinkle Irrigated with Reuse Water

Abstract

Abstract An experiment was conducted on four container-grown tree species placed under five different irrigation reuse water treatments to determine the extent of foliar damage after a 14.5-month period. The tree species included Heritage oak (Quercus virginiana Mill. ‘Heritage’), desert willow (Chilopsis linearis (Cav.)/Sweet), flowering plum (Prunus cerasifera Ehrh ‘Atropurpurea’), and Chinese pistache (Pistacia chinensis Bunge). Plant response and an index of visual damage (IVD) were assessed at different times throughout the experiment. Ion concentrations in the leaf tissue were different for species (S) (p < 0.001), treatment (T) (Na, K, SO4, p < 0.05) and by a species by treatment interaction (S × T) (Na, Ca, Mg, K and SO4, p < 0.05). SPAD measurements varied by S (p < 0.001), T (p < 0.001) and by an S × T interaction (p < 0.045). SPAD measurements decreased as the leaf tissue Na concentration increased (SPAD = 47.49 – 12.46(Na), r2 = 0.38, p < 0.01). The IVD varied by S (p < 0.001), T (p < 0.001) and by an S × T interaction (p < 0.001). Na, Ca and SO4 tissue ion concentrations could account for 52% of the variability in the IVD (IVD =−1.93 + 4.63(Na) + 2.60(Ca)−0.001(SO4), p < 0.01). Because the irrigation treatment resulting in the lowest IVD was species dependent, irrigation treatment selection should be based upon an evaluation of the landscape species composition and the potential cost of implementing a given strategy. The response observed in this study suggests that a single universal irrigation strategy does not exist, indicating that emphasis must be placed on initial and replacement plant selection.