Influence of plants on the salinity of constructed wetlands effluents.

Abstract

Reuse of constructed wetlands effluents for fertigation is a promising practice in regions that suffer from water scarcity. Thus this study aimed to evaluate the influence of Vetiver (Chrysopogon zizanioides) and Tifton 85 (Cynodon sp.) grasses cultivation on salinity of the saturated solution of the Horizontal Subsurface Flow Constructed Wetlands (HSSF-CW) porous medium. The grasses were cultivated in HSSF-CW mesocosm and submitted to different levels of salinity for six months. The crop's evapotranspiration, biomass productivity, the electrical conductivity variation (ΔEC) in the solution under treatment and the water use efficiency (WUE) of these grasses were evaluated. The cultivation of Vetiver and Tifton 85 in HSSF-CW provided an increase in the electrical conductivity of the solution mainly for the lowest levels of affluent salinity. The ΔEC in HSSF-CW grown with Vetiver and Tifton 85 grasses were 90.20 and 27.13 mS cm-1, respectively. Meteorological variables maximize the effect of the vegetative development in ΔEC of the solution. The WUE values of Vetiver and Tifton 85 grasses were 1.77 and 4.18 g kg-1, respectively. Thus plants with high water use efficiency such as Tifton 85 is indicated for HSSF-CW in which the effluents are used in the fertigation of agricultural crops.