Impacts of Reclaimed Water Irrigation on Soil Salinity, Nutrient Cycling, and Landscape Plant Growth in a Coastal Monsoon Environment

Abstract

This study investigated the impacts of reclaimed water (RW) irrigation on soil properties and landscape plant growth in a coastal monsoon city over a 13-month period. Soil properties in plots irrigated with RW and tap water (TW) were monitored monthly, including electrical conductivity, total nitrogen, total phosphorus, soil organic matter, and overall variations of soil enzyme activities. The results show that RW irrigation led to increased fluctuations in soil salinity indicators, with higher peaks during periods of low rainfall. Rainfall can efficiently mitigate the salinity increase associated with RW irrigation, highlighting the influence of monsoon climate variability on salinity dynamics. RW application increased soil total nitrogen and organic matter and decreased soil total phosphorus. This suggests that RW irrigation induces complex nutrient interactions within the soil–plant system. Furthermore, RW irrigation promoted the activities of soil enzymes related to carbon, nitrogen, and phosphorus cycling, indicating potential alterations in nutrient bioavailability. Plant growth responses varied among species, with Nephrolepis cordifolia and Cordyline fruticose exhibiting signs of salt stress, especially in the initial months of planting in RW plot. Other species demonstrated greater tolerance to RW irrigation, suggesting the importance of species selection for sustainable landscape management with RW. This study demonstrates the challenges and opportunities associated with RW utilization for urban greening.