As the environmental impact of industrialized monoculture farming has become increasingly evident, agriculturists, botanists, and gardeners interested in more sustainable foodways have looked to Indigenous agricultural practices and traditions to grow crops in closer collaboration with the land. A Haudenosaunee (Iroquois) crop system known as the Three Sisters has become more widely known as an example of polyculture farming and potential alternative model to the ravages of modern industrial agriculture. The name refers to the practice of growing three crops—beans, squash or pumpkin, and maize—together in a single section of land, a technique also known as intercropping or interplanting.
In her 2013 book Braiding Sweetgrass, Potawatomi botanist Robin Wall Kimmerer explained that these crops thrive together because maize provides a trellis-like framework for nitrogen-fixing beans to grow on while the low-lying squash provides a productive ground cover crop. The US Department of Agriculture’s National Agricultural Library notes that this practice was so imbricated with some Native cultures that it figures in Seneca and Iroquois creation myths. The combination of crops has also been celebrated for its well-balanced offering of basic nutrients of proteins and carbohydrates, and Jane Mt. Pleasant, an agricultural scientist of Tuscarora descent, further finds that growing the crops together produced more protein and energy per hectare than growing any singular crop or combination of singular crops in the same area.
Mt. Pleasant writes that although the Three Sisters are often discussed together and that the Haudenosaunee typically interplanted the Three Sisters, “they could also have planted monocultures of the individual crops to meet specific needs” beyond sustenance such as for external trade. Consequently, she quantifies and compares the productivity of each crop planted as both monocultures—one crop in any given area—and as the interplanted polyculture. She notes that even if the crops were planted alone in a given area, however, all three would be planted in some way and have formed part of the diet.
Bean and squash yields (as measured by weight) were reduced when intercropped with maize, while maize yields were only slightly diminished when intercropped. This might beg the question of the benefit of interplanting if crops don’t provide their maximum yield, but comparing the nutritional yield of polyculture versus monoculture parcels of land demonstrated that interplanting yielded greater nutritional value per hectare despite the lower crop yields.
Mt. Pleasant finds that “the Three Sisters produced two to four times more energy” and more protein per hectare than the same area planted with monocultures of all three crops. Assuming an adult who consumes 2500 calories and 60 grams of protein a day, she estimates that each hectare of the Three Sisters could provide enough energy for about thirteen people and enough protein for about fifteen people in a year, as compared to the respective yields of eleven and thirteen people per hectare when multiple monocultures were planted.
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According to Mt. Pleasant, the more efficient nutrient yield of the Three Sisters occurs because beans and squash provide substantial quantities of protein that supplement the high energy and volume yield of maize. Maize provides the nutritive backbone to the Three Sisters system, yielding the bulk of the energy and a modest amount of protein. Even if not at their maximum crop yield, protein-rich beans, pumpkin flesh, and pumpkin seeds yield additional protein that compensates for the slightly diminished crop yields. Mt. Pleasant concludes that “with the Three Sisters, farmers harvest about the same amount of energy as from maize monoculture, but they get significantly more protein yield from the inter-planted bean and pumpkin.” Thus, even if a farmer primarily relied on corn for sustenance and/or trade, planting beans and squash alongside the maize increased the nutritive value of the same area.
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Mt. Pleasant explains that beans and squash also provide other minerals and nutrients that maize less readily provides, such as tryptophan, the allegedly sleep-inducing chemical that turns into the vital nutrient niacin (Vitamin B3). Maize provides this only through the process of nixtamalization (soaking or cooking the kernels in an alkaline solution like when making tortillas), but beans and pumpkin seeds provide tryptophan without additional processing, further enhancing the nutrient yield of a single interplanted area.
Mt. Pleasant’s study indicates that a significant benefit of the Three Sisters system is modestly space-efficient production of a nutritious diet. More importantly, the system also challenges us to think beyond the modern industrial motive to maximize production of volume and to consider less immediately obvious benefits that can be reaped when we sow creatively.
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