Urban Agriculture: Assessing the Effectiveness of Polyculture Farming

Cameron Murray


This summer, a number of studies related to urban agriculture were conducted at the URI  Gardner Crops Research center, a vertically-layered annual polyculture (VLAP) trial being one of them. Urban farmers are looking for methods of farming that will allow them to maximize land use. The purpose of this trial was to test the effectiveness of VLAPs. This trial employed a  randomized plot design with 4 replicates and three treatments: sweet potato in monoculture,  Tarbais bean (a high value specialty crop) in monoculture, and a polyculture consisting of both crops. Each plot was divided into three 0.762 by 4.57m (2.5x 15ft) beds, 1.22m (4ft) in the center. Trellises 1.98m tall and 2.44m wide (6.5x 8ft) were constructed over the beds. Crops were maintained until harvest in mid-October. The results showed that the polyculture plots over yielded based on the land equivalence ratio. Both bean yield and sweet potato yield were reduced in polyculture, but complementary between the two crops resulting in overyielding in polyculture compared to the monocultures. Adding sweet potato to Tarbais beans increases the plot-level value compared to beans alone but adding beans to sweet potato does not. Future experiments should explore different crop combinations.