CAREER: Effects of Urban Agriculture Expansion and Climate on Nutrient Cycling and Loss in Urban Ecosystems

University Of St. Thomas, Saint Paul MN

Investigators

Abstract

Urban agriculture is rapidly expanding in many cities worldwide. Because compost is generally used as fertilizer, urban agriculture has the potential to recycle nutrients from food waste back into the human food system. However, the availability of nutrients in compost may not match the nutrient demands of crop production, and imbalanced or excessive application of compost could lead to losses of nutrients through leachate or runoff. In some cases, urban agriculture could be a contributor to the pollution of groundwater or surface water. Additionally, changes in the frequency and intensity of precipitation have the potential to affect nutrient loss rates from urban farm plots. Although nutrient dynamics in conventional agriculture have been well studied, little is known about controls on nutrient cycling in urban agriculture, which occurs at a different scale and is subject to different management strategies. This research will quantify and contextualize the role of urban agriculture on nutrient dynamics within the Twin Cities, Minnesota urban ecosystem. Project results will be shared with local policy-makers as well as with the scientific community. Approximately 140 undergraduate students will be engaged in project activities each year through courses, and this project will provide intensive research experiences for approximately 15 undergraduate students and 5 high school interns. This project will combine data collection from urban farms and community gardens, and experimental manipulations across study plots at the University of St. Thomas, Minnesota. The observational component will characterize the range and frequency of different soil management techniques, and to assess how these different management strategies result in different levels of nutrient use efficiency and nutrient export. Researchers will construct nutrient budgets for ten urban farms based on information collected from farm managers on compost application and produce yield, and will collect additional data on soil and leachate nutrient levels. Additionally, researchers will use a controlled, replicated experiment, using 96 four square meter raised bed plots, to measure the effects of compost type and application rate, and simulated rainfall intensity, on nutrient use efficiency and loss via leachate. Finally, statistical models based on these results will be used to estimate cumulative nutrient fluxes from urban agriculture at the city scale, under current and future scenarios.