Department or Program

Environmental Studies


The Three Sisters polyculture is an Iroquois method of farming consisting of mounds of corn, beans and squash. This system has been practiced in the modern-day region of the northeast United States for well over two thousand years. The scientific literature that exists on this subject generally agrees that the polyculture system tends to be more productive and have positive benefits to soil health and condition. For this thesis, a study was set up that compared Three Sisters mounds side-by-side with monoculture plots of corn, beans and squash. With the goal of understanding any differences between the polyculture and monoculture plots, soil samples were collected and analyzed for nutrient content and availability, soil health and fertility, and soil abiotic characteristics. Additionally, plants and vegetables were harvested and weighed to track any above- ground differences that might be related to the different planting methods. The results showed that many of the soil characteristics were insignificantly different between the two systems, with the exceptions of soil moisture (squash monocultures had significantly higher soil moisture than every other treatment) and soil temperature (during the hottest part of the growing season, squash monocultures had lower soil temperature than the other plots). The plant data showed that the beans and squash in the monoculture had a higher yield than those in the polycultures and that the corn and beans in the monocultures had higher plant biomass than their polyculture equivalents. For more accurate results, this study would have to be spatially and temporally expanded to minimize the effect of natural variation of the plots and to allow for the no-till elements of the polyculture to establish.

Level of Access

Restricted: Campus/Bates Community Only Access

First Advisor

Carissa Aoki

Date of Graduation


Degree Name

Bachelor of Arts

Number of Pages



Available to Bates community via local IP address or Bates login.