Wastewater impact on physiology, biomass and yield of canola (Brassica napus L.)

The impact of domestic/municipal wastewater (mww) of Dera Ismail Khan, Pakistan was assessed through its effects on biomass, physiology and yield of canola (Brassica napus L.). The pot experiments were conducted in a completely randomized design with three replications in net house during winter season 2006-07 and 2007-08 at Gomal University, Dera Ismail Khan, Pakistan. Treatments included were T0 (tube well/tap water), T1 (20% mww), T2 (40% mww), T3 (80% mww) and T4 (100% mww/raw-form municipal wastewater). The quality and chemical composition of wastewater was deviating from international (Anon., 1985) as well as NEQS (2005) standard. Analysis of wastewater showed that biochemical oxygen demand (BOD), chemical oxygen demand (COD), sodium adsorption ratio (SAR) and total suspended solids (TSS) were above the permissible limit of irrigation. In pods per plant, the reduction was 61.55% by recording 110 pods per plant with T4 (100% mww) as compared to control T0 (286.1 pods per plant). Similarly pod length (reduced by 59.72%), seeds per pod (reduced by 42.53%), Seeds per plant (reduced by 82%), seed weight per plant (reduced by 88%), 100-seed weight (reduced by 19.54%) and straw yield (reduced by 54.23%) were significantly reduced by applying 100% wastewater. The most affected yield contributing traits were seeds per plant and seed weight per plant with 82% and 88% reduction, respectively due to T4 (100% mww). On average, the decrease was 60% in the first stage and a further decrement of 4.83% was observed when the obtained seeds were re-sown in 2007-08. Results revealed that utilizing municipal wastewater of the area under investigation for irrigation purpose of food and feed crops might not be safe. The major reason seems to be the high salinity and sodium adsorption ratio that restricted crop growth and yield.