Production benefits of community-created vermicompost and worm juice in a South African township

As urbanization increases globally, many residents of cities face challenges from food insecurity and general poverty. In sub-Saharan Africa (SSA), many migrants to cities come from rural, agricultural backgrounds and may be eager to farm in community or kitchen gardens for nutritional, economic, and social benefits. However, soil nutrient deficiencies and other constraints on production limit potential gains from urban agriculture. As a result, low-cost innovations to increase production could provide important community benefits. Here, we report on results from an experiment to assess the production value of worm-generated, food-waste compost created by a community initiative in Khayelitsha, South Africa, one of the largest and fastest growing urban settlements in South Africa. We first describe a community-embedded program for generating worm-based compost (“vermicompost”) and “worm juice” (liquid extracts from the composting process). We then describe an experiment conducted in the community in which we field tested the effects of vermicompost and worm juice addition on the growth of Swiss chard, a common winter crop at this location. We grew plants in one of three levels of vermicompost addition (0%, 10%, 20%) either with or without worm juice in a fully factorial design. We found that 10% and 20% vermicompost significantly (P < 0.0001) increased chard yield (by ~51% and ~59% respectively), and worm juice also significantly increased yield (p = 0.024). Soil analyses indicated that vermicompost addition reduced soil pH and increased soil P levels. These results suggest that a community-embedded, grassroots vermicomposting operation can substantially increase yields for urban farmers, thereby increasing the economic and social benefits that emerge from community and kitchen gardens in marginalized urban areas.