Effect of Reclaimed Water and Drought on Salt-sensitive Perennials

Abstract

Four species of salt-sensitive perennials (Chilopsis linearis, Tecoma stans, Salviagreggii, and Verbena pulchella gracilior) were grown in containers and were irrigated with potable or reclaimed water. Electrical conductivity (EC) was 0.3 dS·m-1 for potable irrigation water and 1.0 dS·m-1 for reclaimed irrigation water. After 12 weeks of growing plants with reclaimed vs. potable water, C. linearis leaf dry weight was reduced by 15%, T. stans root dry weight was reduced by 41%, V. puchella gracilior stem dry weight was reduced by 35%, and S. greggii total dry weight was reduced by 56%. The increase in canopy size was calculated 4, 8, and 12 weeks after treatments began and was not affected by water source for C. linearis and T. stans, but was reduced for S. greggii and V. pulchella gracilior treated with reclaimed water. Up to 12% dieback and reduced flowering were observed on S. greggii irrigated with reclaimed water. Within 4 weeks of treatments, EC in the root zone was 0.5 dS·m-1 for plants irrigated with potable water and 1.9 dS·m-1 for those irrigated with reclaimed water. When exposed to drought, C. linearis and T. stans grown with reclaimed water maintained a more negative water potential as soil moisture was depleted. Osmotic potential started to increase significantly for both irrigation treatments when more than 25% moisture from fully saturated containers were lost. In general, plants irrigated with potable water sustained more damage than those irrigated with reclaimed water after recovering from a drought cycle.