A Review of Nutrient Losses to Waters From Soil- and Ground-Based Urban Agriculture—More Nutrient Balances Than Measurements

Urban agriculture has a high potential to contribute local circular economies, for instance by using nitrogen, phosphorus, and potassium in city organic waste streams as fertilizer inputs. However, inefficient use of waste-derived fertilizers could water quality impairment related nitrogen phosphorus losses. Organic derived are particularly challenging from nutrient stoichiometry perspective, making over- under-application particular likely. Where, under what conditions, urban acts net positive economy vs. risk remains unclear. Here we review empirical peer-reviewed studies (2000–2021) on soil- ground-based with stated concern losses water. Of the 20 publications retained reviewed (out 241 screened), only seven measured waters. There were four experimental studies, which three leachate different garden management practices. 16 done real-world quantified leachate; average spanned 0.005 6.5 kg ha ?1 0.05 140 nitrogen. 13 non-experimental provided data inputs harvested crop outputs, be used calculate balances—an indicator efficiency. Although value ranges large, most studied gardens showed surpluses (inputs > harvest) (but not potassium); these identified Contextual factors such access knowledge, along regulations environmental can help explain wide range balance values observed. large surplus was often linked increased losses, it always case limited number identified. Our suggests that more field measure waters, document contextual factors, needed determine how may sustainable all nutrients without nutrient-related impairment.