Adapting the Indigenous Three Sisters system to modern row cropping practices

Abstract

The Indigenous companion planting technique known as the Three Sisters system improves soil health, weed control, and crop yields by combining mutually beneficial crops. However, existing research focuses on small-scale gardening, while modern agriculture’s reliance on large land and machinery makes the traditional garden-based approach impractical. This study is the first to explore the adaptation of the Three Sisters system to modern row-cropping practices. Two-year field experiments were conducted in Manitoba, Canada. The Three Sisters crops, sweet corn (Zea mays L.), pole bean, and summer squash, were grown under four planting modes: corn monoculture, corn with bean companion, corn with bean and squash companion, and squash monoculture. Key measurements included soil moisture content, leaf area index, crop yield components, and soil nitrogen levels. Results showed that companion plots with two or three crops generally had lower soil moisture compared to monocultures, with squash monoculture plots retaining the most soil moisture. Among the companion plots, similar soil moisture levels indicated corn as the dominant water consumer. The leaf area index of squash monoculture plots increased rapidly in mid-season, with plots containing squash achieving the highest indices later in the season. Bean contributions to leaf area index were minimal due to corn canopy dominance during early growth stages and squash canopy dominance later. Monoculture plots produced higher individual crop yields, whereas companion planting offered greater produce diversity and a higher total yield of combined crops. The timing of bean planting had inconclusive effects on corn yields but consistently improved bean yields when delayed. Companion plots with three crops exhibited lower residual soil nitrogen, suggesting potential water quality benefits. This study offers guidance on adapting the traditional Three Sisters system to modern row-cropping practices, presenting a sustainable approach that balances agricultural productivity with ecological and human health benefits.