Long term impact of waste water irrigation and nutrient rates: I. Performance, sustainability and produce quality of peri urban cropping systems

Farmers in peri-urban areas of developing countries depend on wastewaters for their livelihood but with grave health and environmental risks. An 8-year field experiment compared food grain (FGPS), agroforestry (AFS), fodder (FPS) and vegetable (VPS) production systems and quantified responses to fertilizers (NP 25–100%) when irrigated with sewage (SW; EC 1.3 ± 0.3 dS m−1 BOD 82 ± 11, NO3–N 3.2 ± 0.4, NH4–N 9.6 ± 0.5, P 1.8 ± 0.3, K 6.4 ± 0.4 mg L−1) vis-à-vis groundwater (GW). Productivity improved with SW by 14–28% while trends were negative with sub-optimal NP under GW. Partial factor productivity (PFP) averaged 18.0, 11.1, 157 and 149 kg kg−1 NP with GW in FGPS, AFS, FPS and VPS, respectively. Counter figures were 13.8, 8.8, 96 and 56 kg kg−1 NP with SW. Paddy-wheat equivalent yields were 5.5, 1.8 and 19.9 fold under AFS, FPS and VPS with SW. About 40, 33, 75 and 20% of fertilizer NP with SW was sufficient for similar production as with recommended NP and GW in FGPS, AFS, FPS and VPS, respectively. Quality of produce improved in terms of crude protein and the micronutrients in edible parts with SW while toxic metals were within the permissible limits. However, the keeping quality of vegetables was lowered due to faster decay with pathogens contamination (Aerobic bacterial plate counts 5 × 105–4.2 × 108 cfu g−1 and Escherichia coli <2 × 102–7 × 105). Thus, the sewage proved as a vital resource in improving productivity, sustainability and saving fertiliser costs but this may pose health risks because of pathogenic infestation that need to be regulated.