Land can support
TL;DR: "Land can support: x" for plant A means "Current 4x4 cell can continuously support x A without fertilizers or water added"
I think I know what the "Land can support" number means and since a quick search showed no info on that on the forum and wiki there goes this post..
From basic experiments with corn seeds, a soil sampler and and a bit of land I gathered that:
-> There is a "soil state" grid with 4x4 cells (so not aligned to the claim grid).
-> Farming variables (nutrients, temperature, rain, etc) are uniform across those 4x4 cells
I think that:
~> The "Land can support" value for a particular plant is the number of plant you can farm renewably on this 4x4 cell without depleting the nutrients and hence use fertilizers. So a "land can suppport" of 16 (4x4) or more is a perfect value.
(I hope this is not viewed as spoilers and that I'm not misinforming)