Response of tall fescue to the reclamation of severely saline coastal soil using treated effluent in Bohai Bay

Abstract

To evaluate the response of tall fescue (Festuca arundinacea) to the reclamation of severely saline coastal soil with different levels of treated wastewater effluent, a field experiment was conducted in 2015–2016. The treated effluent was saline (EC, 4.2–6.9 dS/m), and five treatments of irrigation water were blended with treated effluent (0%, 25%, 50%, 75% and 100%) and fresh groundwater. The saline soil contained a gravel-sand layer imbedded at depth of 60 cm to cut off the capillary porosity. Irrigation were applied by micro-sprinkler, and the irrigation management was divided into salt-leaching stage (including enhanced salt leaching and water-salt regulation) and normal irrigation stage. The result indicated that during these stages, the leaf chlorophyll content increased as the percentage of treated effluent increased because the main stress was from fertility rather than salinity. During the normal irrigation stage, the leaf proline content increased to 1759.0, 1970.7, 2388.8, 2699.7 and 2820.3 μmol/g in the rainless season, after which it decreased to 485.8, 486.0, 515.9, 513.8 and 561.5 μmol/g in the rainy season. Treated effluent had no significant effect on the root amount of tall fescue, but led to greater root distribution in the shallow layer, except for the 100% treatment because of the induced increase in surface soil salinity. During salt-leaching stage, soil salinity did not clearly affect the yield of tall fescue. The yield generally increased as the treated effluent percentage increased because of the fertility value, while during dry season of normal irrigation stage, the accumulated soil salinity decreased the yield. Overall, the reclamation method using treated effluent is feasible for tall fescue. Based on the method, the appropriate percentage of treated effluent of total applied water (including irrigation and rainfall) was below 70%–80%.