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

Abstract

tFarmers in peri-urban areas of developing countries depend on wastewaters for their livelihood but withgrave health and environmental risks. An 8-year field experiment compared food grain (FGPS), agro-forestry (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−1BOD 82 ± 11, NO3–N 3.2 ± 0.4, NH4–N9.6 ± 0.5, P 1.8 ± 0.3, K 6.4 ± 0.4 mg L−1) vis-à-vis groundwater (GW). Productivity improved with SW by14–28% while trends were negative with sub-optimal NP under GW. Partial factor productivity (PFP)averaged 18.0, 11.1, 157 and 149 kg kg−1NP with GW in FGPS, AFS, FPS and VPS, respectively. Counterfigures were 13.8, 8.8, 96 and 56 kg kg−1NP with SW. Paddy-wheat equivalent yields were 5.5, 1.8 and19.9 fold under AFS, FPS and VPS with SW. About 40, 33, 75 and 20% of fertilizer NP with SW was sufficientfor similar production as with recommended NP and GW in FGPS, AFS, FPS and VPS, respectively. Qualityof produce improved in terms of crude protein and the micronutrients in edible parts with SW while toxicmetals were within the permissible limits. However, the keeping quality of vegetables was lowered due tofaster decay with pathogens contamination (Aerobic bacterial plate counts 5 × 105–4.2 × 108cfu g−1andEscherichia 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 infestationthat need to be regulated.