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

都市农业正在全球许多城市迅速扩张。 由于堆肥通常用作肥料，城市农业有潜力将食物垃圾中的营养物质回收回人类食物系统。 然而，堆肥中养分的可用性可能无法满足作物生产的养分需求，堆肥的不平衡或过度施用可能会导致渗滤液或径流造成养分损失。 在某些情况下，城市农业可能是造成地下水或地表水污染的一个因素。 此外，降水频率和强度的变化有可能影响城市农田的养分流失率。 尽管传统农业中的养分动态已得到充分研究，但对城市农业中养分循环的控制知之甚少，城市农业发生在不同的规模上，并受到不同的管理策略的影响。 这项研究将量化和具体化城市农业对明尼苏达州双城城市生态系统养分动态的作用。 项目结果将与当地政策制定者以及科学界分享。 每年大约有 140 名本科生将通过课程参与项目活动，该项目将为大约 15 名本科生和 5 名高中实习生提供深入的研究经验。该项目将结合来自城市农场和社区花园的数据收集，以及明尼苏达州圣托马斯大学研究地块的实验操作。 观测部分将描述不同土壤管理技术的范围和频率，并评估这些不同的管理策略如何导致不同水平的养分利用效率和养分输出。 研究人员将根据农场管理者收集的有关堆肥应用和产量的信息，为十个城市农场制定养分预算，并将收集有关土壤和渗滤液养分水平的额外数据。 此外，研究人员将使用 96 个四平方米的高床地块进行受控、重复实验，测量堆肥类型和施用率以及模拟降雨强度对养分利用效率和渗滤液损失的影响。 最后，基于这些结果的统计模型将用于估计当前和未来情景下城市规模的都市农业的累积养分通量。

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.