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Urban Agriculture

Urban agriculture is a global and growing pursuit that can contribute to economic development, job creation, food security, and community building.  It can, however, be limited by competition for space with other forms of urban development, a lack of formalized land use rights, and health hazards related to food contamination.  The use of green roof technology in urban agriculture has the potential to alleviate some of these problems, without adversely affecting the benefits provided by urban agriculture.  It would not only enable the use of land for development and agriculture, but may facilitate the formation of formal space and water use agreements and enable redistribution of ground level resources among urban farmers.  This could decrease the use of contaminated land and water at ground level and alleviate health concerns.  Before green roof technology can be incorporated into urban agriculture on a larger scale, installation costs must be reduced, roof weight limitations should be assessed, and appropriate management practices developed which will ensure that the benefits of green roofs, such as energy energy savings and storm water management, are still provided to urban communities.

A review of green roofs and urban agriculture is published in:
Whittinghill, L.J. and D.B. Rowe.  2012.  The role of green roof technology in urban agriculture.  Renewable Agriculture and Food Systems 27(4):314-322.

a man standing amidst a green roof herb garden
An herb garden on a hotel in Vancouver, BC

Vegetable Production on Extensive Green Roofs

Rooftop vegetable gardening is a production system in urban agriculture based on green roof technology.  To broaden the scope of this practice, the use of relatively shallow substrate depths must be explored, since most existing flat roofs are unable to support much added weight.  Three growing systems, a 10 cm deep green roof, raised green roof platforms with 10 cm of substrate, and in-ground were evaluated for vegetable and herb production over three growing seasons (2009-11).  Tomatoes (Solanum lycopersicum), green beans (Phaseolus vulgaris), cucumbers (Cucumis sativus), peppers (Capsicum annuum), basil (Ocimum basilicum) and chives (Allium schoenoprasum) were studied because of their common use in home gardens.  All plants survived and produced biomass in all growing systems and yielded crops large enough for analysis except pepper in 2009 and 2010.  Overall, yields and basil biomass were higher and of better quality in-ground during 2009, the only year in which irrigation was applied,, and similar on the green roof and platforms.  Variability in success was partially due to annual weather variation with the greatest impact on cucumber.  Yields of chive, a perennial crop, were not affected by growing system after the first year.  Results suggest that with proper management, vegetable and herb production in an extensive green roof system is possible and productive.

Complete results are published in:
Whittinghill, L.J., D.B. Rowe, and B.M Cregg.  2013.  Evaluation of vegetable production on extensive green roofs.  Agroecology and Sustainable Food Systems 37(4):465-484.

research platforms being irrigated
Growing vegetables in roof platforms (August 2011

Nutrient Management and Mulching Strategies for Vegetable Production on an Extensive Green Roof

Substrate nutrient and moisture management are two major concerns in green roof agriculture.  These concerns are amplified when using extensive green roof systems for food production.  Currently no recommendations or best management practices exist to guide rooftop farmers in dealing with these issues.  The purpose of this study was to explore three mulching strategies (no mulch, pine bark mulch, and a living Sedum mulch) and three fertilization regimens (25, 50, and 100 g/m2 of a 14-14-14 N-P-K slow release fertilizer applied twice during each growing season) over two growing seasons to determine their possible benefits to rooftop vegetable and herb production.  Tomatoes (Solanum lycopersicum), beans (Phaseolus vulgaris), cucumbers (Cucumis sativus), sweet peppers (Capsicum annuum), basil (Ocimum basilicum), and chives (Allium schoenoprasum) were included in this study because of their common use in home gardens.  Crops performed better in 2010 than 2011 because of more extreme temperature and precipitation variations during 2011.  When there were differences among mulch treatments, pine bark usually resulted in higher productivity than the live Sedum mulch.  Mixed effects of live Sedum mulch on crop production are consistent with previous literature on the use of living mulches in vegetable production. Among fertilizer treatments, 100 g/m2 outperformed lower rates in most cases.  Instances of higher performance of lower fertilizer rates were observed, likely because those treatments adequately supplied the crops with phosphorus and potassium.  Further research into more types of mulch and their effects on the green roof microclimate could provide a better understanding of the role that mulching could play in green roof agriculture.  Likewise, more research into various types of fertilizers with different compositions could also help in the development of an efficient and productive nutrient management practice.

Complete results have been submitted for review prior to publication.

research platforms at htrc
Fertility and mulch effects on vegetable production

Stormwater Runoff Quantity and Quality from Vegetable Producing Green Roofs 

See discussion under stormwater management.

Effect of Substrate Organic Matter Content on Vegetable Production

See discussion under substrates.

Bailey Hall Green Roof Project – Growing Food for Dormitory Residents

During May 2013, a section of Bailey Hall was converted to a green roof dedicated to growing vegetables.  The overall objectives of the project are to provoke an interest in sustainability in the Brody student community, harness efficiency of land usage by taking advantage of rooftop space, and to encourage Bailey residents to actively participate in a sustainable, ecological lifestyle.  The project will research the effectiveness of growing organic edible crops in a rooftop environment.  In addition, the project will assess Brody Neighborhood residents’ knowledge of rooftop gardens and sustainability, their attitudes towards the adoption of eco-friendly procedures, and what can encourage residents to take better care of their environment. Other benefits of the rooftop garden include the production of organic crops that would be consumed in Brody cafeteria.

This project is an undergraduate MSU Residential and Hospitality Services Neighborhood Collaboration Project and is a collaboration between the Department of Horticulture, the Department of Community, Agriculture, Recreation and Resource Studies, and the MSU Student Organic Farm.

bean plants attached to a railing
Pole beans climb the fence

delicious looking basket of fresh produce - cucumbers, onions, apples and green beans
Vegetables from the UK

Four rows of vegetablesStudents tend the vegetables and flower gardens which provide a hands on learning experience at the Gary Comer Youth Center in the south side of Chicago

close up of green roof vegetablesGrowing vegetables in shallow substrate depths (12 cm) on the Plant and Soil Sciences Bldg  (August 2011)

research platforms with different types of mulch
Comparing effect of live sedum mulch, pine bark, and no mulch on vegetable production

strawberries and chives on a green roof - a parking lot in the back
Strawberries on the MSU Bailey Hall green roof

green roof grown tomatoes
Tomatoes on the MSU Bailey Hall green roof

Cucumbers on the MSU Bailey Hall green roof
Cucumbers on the MSU Bailey Hall green roof