Maize, beans and squash in one field feed more people than any of them alone

Modern agriculture is organised around single crops in single fields, because that is what machines and markets prefer. The assumption underneath it is that specialisation produces more food.

Jane Mt.Pleasant, an agronomist at Cornell, tested that assumption against a system that predates it. She measured the Haudenosaunee Three Sisters — maize, beans and squash grown together — against the same crops grown separately.

The polyculture won.

What was measured

12.25m

kilocalories produced per hectare

349 kg

protein produced per hectare

13–16

people fed per hectare per year, depending on whether you count energy or protein

The paper's finding is stated plainly: the Three Sisters yields more energy and more protein than any of the crop monocultures or mixtures it was compared against. Converted into people, it supplies energy for 13.42 people per hectare per year and protein for 15.86.

Why growing them together works

Each plant does something the others need.

Maize grows tall and provides a structure for climbing.

Beans climb it, and fix nitrogen in the soil through bacteria in their root nodules — fertilising the field that the maize is drawing from.

Squash spreads broad leaves at ground level, shading out weeds and holding moisture in the soil.

The three occupy different heights, different root depths and different niches. They are not competing for the same resources in the same place, which is why the field produces more in total than the same ground split three ways.

The cooking is part of the system

The study also looked at nutrition, and found the processing method matters as much as the crop.

Nixtamalization — cooking maize in an alkaline solution before grinding — increases the calcium the body can absorb and improves protein quality. Maize and beans together already complement each other's amino acid profiles; nixtamalized maize with beans and squash is close to a complete diet.

That is not a happy accident. It is a food system worked out over a very long period, in which the agronomy and the cooking were developed together.

The catch, which the newer research names

A 2025 study in Plants, People, Planet looked at the same comparison with labour included, examining yield, growth and labour demands of the three crops in monoculture versus the Three Sisters.

Labour is the honest qualifier on any polyculture. A field with three intermingled crops at three heights resists mechanisation. Planting, weeding and harvesting are more hand work than a single-crop field of the same size.

Which is much of the reason the system was displaced. Not that it produced less food per hectare — by Mt.Pleasant's measurements it produced more — but that it produced less food per hour of labour and per machine, and those are the numbers industrial agriculture optimises for.

Worth knowing when the phrase "more productive" is used without saying productive of what, per unit of what.