Chinampa farming was central to the Aztec way of life and fed much of the empire.
Chinampas are raised beds of soil which were constructed in lakes around Mexico, especially in Lake Texcoco. After pounding wooden stakes into the lake bed and fastening them together together with reeds, the Aztecs would dredge up lake silt and organic material and pile it in the wooden enclosure.
They would then plant maize, beans, squash, sweet potatoes, and/or willow trees into the agricultural plot. Maize, beans, and squash, and sweet potatoes provided most of the food in the Aztec world, while the willow trees quickly rooted and secured the Chinampa garden to the lake bed.
Because the Aztecs lacked large draft animals, they also lacked manure for fertilizer. As such, the Aztecs developed a system of public outhouses which were built on top of canoes. Once full, the canoes would bring human feces to agricultural regions and use it for fertilizer.
The combination of highly fertile lake soil, a constant supply of water, and an abundance of fertilizer made Chinampa gardening one of the most productive agricultural methods on the planet. Some estimates suggest that Chinampas could reach a crop yield of seven yields per year. This outrageously high number is impressive, but questionable. As such, I usually go with the more conservative estimate of three to four yields per year.