Farming in the City: How Does the Altered Urban Environment Influence Cropping System Productivity, Ecology, and Profitability?

View the project final report

Commodities

• Vegetables: beans, beets, peppers, tomatoes
• Additional Plants: herbs

Practices

• Crop Production: crop rotation, double cropping, multiple cropping, tissue analysis
• Education and Training: demonstration, extension, participatory research
• Farm Business Management: agricultural finance, budgets/cost and returns
• Natural Resources/Environment: biodiversity, indicators
• Pest Management: integrated pest management, weather monitoring
• Production Systems: agroecosystems
• Soil Management: soil analysis, soil microbiology
• Sustainable Communities: local and regional food systems, partnerships, urban agriculture, urban/rural integration

Urban agriculture is a growing trend in the United States, but little is known about the effects of urban abiotic and biotic effects on agroecosystems in cities. Objectives of this study were to use six test gardens in the greater Chicago area to measure the urban microenvironment and compare these measures to crop production, insect abundance and population dynamics, and soil microbe indicators in raised bed pots. Results and objectives were presented at grower field days, presentations at community events, and scientific conferences. Results are in preparation for publication in peer reviewed scientific journals.  Micrometeorological towers measured atmospheric conditions. Temperature and CO₂ were positively correlated with urbanization, whereas relative humidity and overall light interception were negatively correlated. Ground level ozone was higher in the peri-urban sites. Spring and fall planted cool season crop production was correlated with increased temperature and reduced ozone concentrations. Light and CO₂ were most correlated to summer planted warm season crop production. Crop pests corn earworm and cabbage looper had highest abundance in the rural site, whereas European corn borer had similar abundance among the sites. Insect orders Diptera (flies) had lower populations in the peri-urban sites, whereas the order Thysinoptera (thrips) had higher populations in the peri-urban sites. All other orders collected, including common pollinator orders, were not different among the sites. Soil microbial biomass and microbial type did not differ across the urban to rural gradient within the raised beds, but there was differences between spring and fall sampling dates. Economic analysis showed highest overall profitability at an urban site mainly driven by tomato yield at that site, and higher overall profitability of urban sites and lowest overall for peri-urban sites due to low yield of these sites. Early and late crop species were generally more profitable in the urban environment than the peri-urban or rural. This research demonstrates that the urban environment is dynamic and urban farmers can choose crop species and varieties to increase profitability. Further research can focus on microenvironmental differences for further understanding light, temperature, and ozone dynamics, and studies on crop species and variety differences can enhance productivity in the urban setting.

Introduction:

Urban agriculture, the production of food crops within urbanized ecosystems, is a relatively common practice in developing nations and is becoming more prevalent in the U.S. Urban agriculture is viewed by many as a promising method for reducing urban externalities and improving diets, livelihoods, and community cohesiveness in blighted urban areas (Armar-Klemesu, 2000). Studies in Chicago, IL and Oakland, CA demonstrate an increasing concentration of home gardens, community gardens, and commercial farms in urban areas (Taylor and Lovell, 2012; McClintock, 2008). The North Central region of the US is especially well-suited to increasing urban food production because of the post-industrial depopulation of cities like Chicago, Milwaukee, and Detroit. Interest in urban agriculture in city centers in the North Central region has grown significantly as evidenced by the rise of local food movements, farmers markets, and organizations dedicated to urban agriculture.

Urban agroecosystems have unique challenges compared to rural counterparts. Carbon dioxide flux and ambient concentrations are higher in urban settings. Pollutant concentrations in urban areas can flux far beyond baseline levels in rural ecosystems (Trusilova and Churkina, 2008). Potentially harmful pollutant fluxes include primary (NO_x, SO_2, and PM₁₀) and secondary (PAN, O₃, and ethylene) pollutants. Each of these pollutants can, to some degree, limit plant production and alter agroecosystem function. Additionally, decreased albedo and evapotranspiration, and increased thermal admittance causes an urban heat island (UHI) effect, the increase in temperature of urban versus adjacent rural areas (Taha, 1997). Consequently, vapor pressure deficit (VPD) increases which leads to increased plant water stress.

Agroecological function can be effected by the altered urban environment. Effects of UHI are greatest in the spring and fall seasons, at night, and during inversions. Thermally regulated ecological processes, such as germination, flowering, senescence, hatching, or morphogenesis may be affected by UHI in urban agroecosystems (Ziska et al., 2007). Plants in urban agroecosystems are likely to benefit from additional growing degree days and frost free days, but also experience greater heat stress and vapor pressure deficit. In addition to UHI, wind speeds in urban areas tend to decrease due to increased surface roughness causing reduced plant stress, but also better conditions for plant pathogen infection.

Altered abiotic conditions in the urban agroecosystem will likely influence important biological functioning. Soil microbial community composition and diversity in urban ecosystems is markedly different from natural or rural ecosystems (Papa et al., 2010). Most notably, diversity of soil microbial communities tends to decrease with the level of urban soil disturbance. Healthy soil microbial populations are closely linked to soil quality in agroecosystems, but little is known about how soil microbial communities will respond to the complex suite of abiotic stressors in a managed urban environment. The unique microclimate and diversity of plant hosts in urban agroecosystems will also likely alter urban plant pathogen dynamics. Insect dynamics in the urban ecosystem are important because of the potentially beneficial ecosystem services provided (e.g., pollination) and damages incurred (e.g., herbivory) by insects. Insect diversity is generally reduced in urban ecosystems, but often spikes in the urban to rural transitional zone, a common phenomenon in natural ecosystems (i.e., the edge effect or ecotone) (Jones and Leather, 2012).

Armar-Klemesu, M. 2000. Urban agriculture and food security, nutrition and health. Grow, Cities Grow. Food Urban Agric. Policy Agenda, 99–118.

Jones, E. L., and Leather, S. R. 2012. Invertebrates in urban areas: A review. Eur. J. Entomol. 109:463–478.

Kaza, N. 2013. The changing urban landscape of the continental United States. Landsc. Urban Plan. 110:74–86.

McClintock, N. 2008. From Industrial Garden to Food Desert: Unearthing the Root Structure of Urban Agriculture in Oakland, California. Inst. Study Soc. Change.

Papa, S.,G. Bartoli, A. Pellegrino,and A. Fioretto. 2010. Microbial activities and trace element contents in an urban soil. Environ Monit Assess 165:193–203.

Taha, H. 1997. Urban climates and heat islands: albedo, evapotranspiration, and anthropogenic heat. Energy Build. 25:99–103.

Taylor, J. R., and Lovell, S. T. 2012. Mapping public and private spaces of urban agriculture in Chicago through the analysis of high-resolution aerial images in Google Earth. Landsc. Urban Plan.

Trusilova, K., and Churkina, G. 2008. The response of the terrestrial biosphere to urbanization: land cover conversion, climate, and urban pollution. Biogeosciences 5:1505–1515.

Ziska, L. H., George, K., and Frenz, D. A. 2007. Establishment and persistence of common ragweed (Ambrosia artemisiifolia L.) in disturbed soil as a function of an urban–rural macro-environment. Glob. Change Biol. 13:266–274.

In order to improve understanding of urban food production, this project aims to characterize environmental conditions of agroecosystems across an urban to rural gradient in Chicago, IL and use this environmental data to understand variability in crop production of several common vegetable crops, insect population dynamics, and soil microbial dynamics. This project leveraged several entities within the Chicago metropolitan area to set up and manage research plots for the characterization of crop production, soil microbes, and insect populations. Also an advisory board of urban farmers and stakeholders met in fall of 2014 to discuss results and improve coordination for better management and data collection. Farmers and community members met during two field days and two community presentations to listen to results from the trial and interact with the researchers. Researchers presented results at two scientific conferences to peer researchers in the urban ecology and agroecology fields. One scientific journal paper has been completed, and three additional peer reviewed journal articles are being prepared for publication. Further publications, stakeholder meetings, and scientific presentations will gauge performance of this project.