Excess fertility in residential‐scale urban agriculture soils in two western Oregon cities, USA

Abstract

Abstract Small‐scale, residential food gardens are arguably the most common form of urban agriculture (UA) in the world. Despite their ubiquity, we know relatively little about the characteristics of UA soils, in general, and of residential food gardens specifically. We thus sampled soils from 27 residential‐scale vegetable gardens in two western Oregon cities to describe the physical, chemical, and biological characteristics of residential‐scale UA soils. We distinguished growing sites by bed type: in‐ground beds (IGs) and raised beds (RBs). We assessed the proportion of soils that fell within published recommendations for vegetable production for various soil parameters. We found residential‐scale UA soils frequently exceeded recommended ranges for many fertility parameters. We also found differences in carbon/nitrogen ratio, active carbon, and sulfur, with RBs significantly higher than IGs. The excesses likely are due to routine overapplication of compost, soil amendments, and fertilizers by growers across their intensively managed urban spaces. Such overapplication and excess is likely to be exaggerated in RBs compared with IGs.