Pattee,
Thanks for posting this book link. I downloaded a PDF copy from the site and just quickly flipped through. Most of the cultural information is still relevant, including several recommendations for increased lime (Calcium) in the soil.
Quote:
Lime is pre-eminently a requisite for heavy, meaty, rich figs, and all
hard-pans are heavily impregnated with lime, and more or less so with potash,
sulphur and iron, all of which go to make a soil favorable for fig production.
A deficiency of lime in any soil will, cause a fruit to be produced that dries
into a hollow shell of seeds and little meat. We have all seen that kind of
dried fruit.
Air and water will cause hard-pan to disintegrate, thus liberating these
above named values. The tree itself may flourish in any soil deficient in lime,
potash, sulphur and iron, yet the product of the tree will be poor. Again,
hard-pan land when blasted conserves moisture below the pan, as summer
heat cannot evaporate the moistures invariably found beneath, and the tree
will eventually push its roots downward and laterally, thus securing required
moisture at all seasons.