With the increased interest in urban food production and community gardens, many gardeners are constructing raised beds. Constructed raised beds offer potential for better drainage and easier access to the growing area. Constructed raised beds also have the ability to increase yield. Substrates for constructed raised beds are often an afterthought, with little scientific basis for selecting materials or consideration for the broader environmental effects of materials. This study evaluates eight substrates and two crops, kale and basil, for yield and chlorophyll content. The same eight substrates were also evaluated for sustainability factors such as carbon-mineralization (C-min) over time and soil microbial biomass carbon (SMBC). Based on yield alone, the 100% compost substrate resulted in the highest yield across all three crop trials. The native soil substrate had the lowest C-min and SMBC rate. Results varied with season and crop, but yield and C-min indicate a substrate composed of compost/native soil is the best overall.