A proposed and incomplete farming mechanic cobbled together after a bit more research in medieval farming. I've gone down this road a bit before and realized a little need as the PC's in my weekly game have decided to claim a village as their own.
Yield in bushels= ((1d6 per seed bushel sown)+Land Quality + Seasonal Modifiers)/2
Roll a control die (1d6) and if this number is greater then the no of bushels sown the yield is halved.
Seasonal Modifiers haven't been fiugyure out yet but it's safe to keep them in the -4 to +4 range.
Land Quality is rated as per a D&D stat.
After each growing season a plot of land must make a saving throw with a negative modifier equal to the bushels of seed planted. A failed save downgrades the quality of that plot by the no. of seed bushels sown.
Land save is 10+
How much hood do people need to eat ? 12-24 bushels a year in corn (grain) and legumes (beans and peas) seems to be the answer. STR x 1.5 seems to do the trick, characters that don't each this much have an increased chance of illness.
Land can yield 1-3 harvests a year depending on land,climate, and farming techniques used.
Land recovery, each season a plot is fallow a save can be made for that plot to upgrade the land quality by 1 for a plot downgraded due to a failed save from an earlier plot season.