Plant growth and microbial responses from urban agriculture soils amended with excavated local sediments and municipal composts

With increasing urbanization and critical issues of food insecurity emerging globally, urban agriculture is expanding as an agroecosystem with a distinct soil type. Growing food in cities is challenged by legacy contaminants in soils, which necessitates the use of imported, safe soils and composts. To promote the long-term sustainability of urban agriculture, we examined the agronomic potential of constructing safe, locally sourced soils to support food production. We collected composts from four municipal composting facilities in New York City: Big Reuse, Long Island City, Queens (BRL), New York Department of Sanitation, Fresh Kills, Staten Island (DNY), Lower Eastside Ecology Center (LES) and Queens Botanic Garden (QBG). We then created two types of constructed soils using each compost: 100% pure compost and a 50:50 blend of compost and clean excavated sediments from the New York City Clean Soil Bank. We then assessed the growth of tomato, pepper and kale in the constructed soils within a plant growth chamber facility. We found Clean Soil Bank sediments enhanced tomato aboveground biomass production by 98%, kale aboveground biomass production by 50% and pepper plant height by 52% when mixed with compost from BRL. At the same time, Clean Soil Bank Sediments decreased tomato plant height by 16% and aboveground biomass production by 29% in LES compost and tomato plant height by 18% in QBG compost, likely due to compost properties. The addition of Clean Soil Bank sediments showed no decline in the symbiosis of arbuscular mycorrhizal fungi across all composts, which is an important beneficial plant–microbe interaction in agroecosystems. A positive ecosystem service was found when Clean Soil Bank sediments were added to municipal composts, with up to a 74% decrease in greenhouse gas emissions of soil CO2 in BRL compost. The results indicate that urban agricultural soils can be constructed using clean, locally sourced materials, such as composted organic waste and excavated sediments from city development sites to support sustainable urban agriculture while enhancing ecosystem services.