From the ground up: soil best management practices for rooftop farms

As the demand for high quality, local produce rises, urban farming has become an attractive option. With limited space in cities, many are turning to rooftops. But factors like a lack of soil, water supply and roof-bearing capacity and managing nutrient leachate from soil must be addressed for rooftop farming to succeed. Once a fertile soil mix is placed on the roof, it can create a potential problem for downstream waters. An optimal soil mix is key to maintaining yield and quality, minimizing leachate and optimizing efficient inputs of irrigation and fertilizer.

Thomas Whitlow and his team partnered with the Brooklyn Grange, a rooftop farming operation that currently raises vegetables on two roofs in New York City. The team installed equipment to monitor precipitation, drainage and water quality of the leachate. The team also compared novel soil mixes with the mix currently used by the Brooklyn Grange. This mix was originally developed for extensive green roofs which use drought-tolerant plants and was not intended for agricultural production. It drains rapidly and requires frequent irrigation.