Raised beds

Drone-mounted lidar found "raised bed" lines at The Sixty Islands site on the Menominee River that seem to date from about 1000 to 1600AD. That takes in the both Medieval Warm period and part of the Little Ice Age, and in soil that's generally pretty poor, and with a short growing season. An earlier study found maize phytoliths in one bed, so they were growing at least some corn in a region at the hairy edge of doing so. A different study found a bit of charred maize dated to about 1400--in between the high and low temperature periods.

The raised-bed ridges apparently were used and rebuilt repeatedly (sometimes mixing in soil from nearby wetlands). Composting from kitchen waste made them more fertile -- and harder to date. The novelty of this paper lies in using lidar to discover the true extent of the cultivated area--possibly 10 times bigger than expected.

The Science article notes the evidence of maize being grown, and presumes they grew other things. The Cosmos article assumes that the forest environment would make it hard to grow crops--which is silly; they'd deforested the area, as the Science article says, by 1000AD.

An earlier study found maize phytoliths, which being silica don't tell much about DNA. I wonder if they had different breeds more tolerant of the shorter growing season and unexpected frosts, and presumably lower yield, too.

Since wild rice was available, I wonder if corn was a luxury trading crop.