Sustainability of Urban Agriculture: Vegetable Production on Green Roofs

Abstract

The practice of producing vegetables on green roofs has been gaining momentum in recent years as a method to facilitate agricultural sustainability in urban areas. Rooftop gardens are becoming an important part of the recent rejuvenation of urban agriculture, and offers alternative spaces to grow vegetable products for urban markets. Green roofs create spaces for the production of vegetable crops, which then generate opportunities for integrating agriculture into urban communities. However, vegetable production activities on rooftops are currently minimal due to multiple challenges that must be overcome before widespread implementation will occur, and these are presented and discussed herein in great detail. Although intensive green roof systems (>15 cm medium depths) are thought to be most suited for vegetable production, the greatest potential for sustained productivity is probably through extensive systems (<15 cm depths) due to weight load restrictions for most buildings. Thus, shallow-rooted vegetables that include important salad greens crops are thought to be the most suited for extensive systems as they can have high productivity with minimal inputs. Research presented herein agree that crops such as lettuce, kale and radish can be produced effectively in an extensive green roof medium with sufficient nutrient and moisture inputs. Other research has indicated that deeper-root crops like tomato can be produced but they will require constant monitoring of fertility and moisture levels. Vegetable production is a definite possibility in urban areas on retrofitted green roofs using minimal growing substrate depths with intensive seasonal maintenance. Rooftop agriculture can improve various ecosystem services, enrich urban biodiversity and reduce food insecurity. Food production provided by green roofs can help support and sustain food for urban communities, as well as provide a unique opportunity to effectively grow food in spaces that are typically unused. The utilization of alternative agricultural production systems, such as green roof technologies, will increase in importance as human populations become more urbanized and urban consumers become more interested in local foods for their families. Although cultivation of food on buildings is a key component to making cities more sustainable and habitable, green roofs are not the total solution to provide food security to cities. They should be viewed more as a supplement to other sources of food production in urban areas.

Green Roof Research in North America: A Recent History and Future Strategies

“…Green roof substrates are low in organic matter so nutrient supplementation is often required for urban rooftop food production. Selective treatments of synthetic fertilizers may improve yields, but caution is required to prevent excessive stormwater runoff contamination (Walters and Midden 2018;Whittinghill et al 2016).…”

Growing Food on Green Roofs: The First Step of an Interdisciplinary Approach

“…The depth of the substrate layer is also crucial to the success of the green roof; being accepted that plant physiological responses and growth will increase with deeper substrates. However, the greater vegetable crops production potential on green roofs is given by an extensive cultivation bed from 0.08 to 0.15 m high at maximum, due to weight load restrictions for most buildings [9]. Nevertheless, this limit may be adjusted according to the substrate physical properties and the crop selected.…”

“…At the same time, the knowledge about which species are best suited to this cultivation system and their proper management is essential to achieve the desired goals. Research reported by Walters and Midden [9] has shown that lettuce can be produced effectively in a green cover medium with enough nutrient and moisture. Whittinghill et al [13], on the other hand, reported that crops with deeper root system, as tomatoes, require more rigorous monitoring of the fertility and humidity levels of the root environment, as well as deeper knowledge about the basic characteristics of the substrate to be able to properly manage it.…”

Towards the Healthy Community: Residents’ Perceptions of Integrating Urban Agriculture into the Old Community Micro-Transformation in Guangzhou, China

“…However, nowadays, UA is practiced more for social, cultural, and environmental reasons than provisioning [38][39][40]. The forms of UA are community gardens, urban farms, edible school gardens, and roof farms [41][42][43]. UA provides people with many nature contact opportunities.…”