Abstract

The use of wastewater for irrigation is on the rise in developing countries like Pakistan, because of scarcity of good-quality irrigation water. Wastewaters contain plant nutrients that favor crop growth but leave a burden of heavy metals, which can enter the food chain, causing great concern. The present study was undertaken to investigate the effects of surface and subsurface wastewater irrigations on water use efficiency (WUE) and accumulation of trace elements (TE) in the shoots of spinach (Spinacia oleracea L.) grown on a soil column. Wastewater was applied at two levels based on daily pan evaporation (PE) (that is, 50 and 100%). Subsurface wastewater irrigation increased plant growth and WUE better than surface irrigation. Irrigation at 100% PE apparently reduced the WUE. However, WUE was enhanced by subsurface irrigation. Higher concentrations of TE were found in plants irrigated with 100% PE whether under surface or subsurface irrigation. Surface irrigation accumulated more TE in plants than subsurface irrigation. Slightly enhanced accumulation of TE was observed in the 2nd layer (30 to 60 cm) of the soil column under 100% surface irrigation. Subsurface irrigation gave higher concentrations of TE in the lower zone of the soil. Lower moisture was found in the top soil under both irrigation systems, but the middle soil layer had the highest electrical conductivity (EC). Irrigation with 100% PE increased EC more than 50% PE irrigation water. Surface irrigation with wastewater produced slightly greater pH than subsurface irrigation.

Key words: Surface irrigation, subsurface irrigation, wastewater, spinach growth, trace elements.