I'm currently "reading"
Food: A Cultural Culinary History. It's fascinating stuff, and I feel like it's rounding out my perspective on food as well as history.
Right now I'm at the Aztec section which contains the following information: learned from earlier civilizations, Aztecs farmed on floating islands, chinampa (17 long and 100-300 feet wide), able to grow 4 crops of maize a year, and interplanted with willows to keep the soil from eroding. They also irrigated, used intercropping (aka using nitrogen fixers) and terraces, and grew and ate spirulina! It's all very interesting.
I found this picture online:
Isn't that an amazing historical way to grow self-irrigated foods? Anyway, I'm learning a lot. (The focus of the lectures is mostly on cooking and history, but the ways foods have traveled, tastes have changed, and the development of agriculture all feed into it. I feel smarter already from listening to it, although I may have to listen to it twice to get everything. We'll see.)
And here's a quote from
another site on the topic:
These data clearly indicated that during radiation frost conditions, a microclimate develops that is considerably and consistently warmer then the air above a similarly positioned dry land field.
...
The author concludes that sub-irrigation has been overemphasized as a feature of both pre-Hispanic and modern wetland agriculture, while frost risk reduction has been an under appreciated result of the creation of chinampa agriscapes. Restoration of past water levels in the chinampa canal system may be desired primarily to achieve increased frost risk reduction, not sub-irrigation
Wikipedia says up to seven harvests per year! And this:
They were created by staking out the shallow lake bed and then fencing in the rectangle with wattle. The fenced-off area was then layered with mud, lake sediment, and decaying vegetation, eventually bringing it above the level of the lake.
Also wikipedia:
There is evidence that the Nahua settlement of Culhuacan, on the south side of the Ixtapalapa peninsula that divided Lake Texcoco from Lake Xochimilco, constructed the first chinampas in C.E. 1100
So we're talking very old permaculture techniques that were probably perfected over hundreds of years. The richness of hugelkultur and soil building techniques, protection from frost, as well as irrigation and extra harvests. Wow!!
Fascinating stuff. Maybe you guys already knew about this but I feel like I'm just scratching the surface in traditional growing techniques.