Modelling nitrogen and phosphorus dynamics in soil fertigated with decentralised wastewater treatment effluent

Many residents in informal settlements lack proper sanitation. The decentralised wastewater treatment system (DEWATS) is a low-cost water borne onsite technology that can potentially provide sanitation in unserved areas. The management of DEWATS effluent is of environmental concern. Its use in agriculture helps improve livelihood and food security in peri urban areas. This study investigated environmental sustainability for fertigation using DEWATS effluent through modelling N and P dynamics in fertigated soils. The SWB Sci model, a crop growth and nutrient (N and P) simulation model was calibrated and validated based on field experiments conducted. The crop growth sub-model was successful and met all statistical criteria (r2 > 0.8 and D > 0.8). Use of DEWATS effluent showed to increase soil inorganic N and P within the top soil layers (0.3 m), which may be beneficial for crop production. However, proper management practices are recommended to prevent leaching and runoff losses.