Does Heirloom learn from my past harvests to predict yields?

Not on its own: you stay in charge of your numbers, and your records show you exactly what to change. Availability follows your plan, not what you recorded before.

Your recorded harvests show where the plan is off, in Season Harvests. Adjust that crop’s yield or harvest window in your Charts, and your new plantings start from your farm’s own figures.

See Compare season harvests with the plan and Set your yields and prices.