Wheat fields produce wheat (obviously).
The wheat field works on a 10 day cycle:
Day 1 : Plough your Field (work is strength related)
Day 2 : Sow your Field (work is intelligence related)
Day 3 : Growing (nothing needs doing)
Day 4 : Growing (nothing needs doing)
Day 5 : Growing (nothing needs doing)
Day 6 : Growing (nothing needs doing)
Day 7 : Growing (nothing needs doing)
Day 8 : Growing (nothing needs doing)
Day 9 : Growing (nothing needs doing)
Day 10 : Harvest your Field (work is strength related)
When you sow the field on day two, remember to place a bag of wheat in your property inventory. If you don't, the worker will get paid but your field won't be sown.
If you employ your workers at 0 stats, you will normally get 8 wheat bags.
If you employ your workers at 20 stats, you will normally get 10 wheat bags.
Assuming that you sell your wheat for 13.20 pounds (the normal price at the Town Hall) then the calculation goes like this.
0 stats : (7x13.20)-(16x3)=44.40 pounds profit.
20 stats : (9x13.20)-(20x3)=58.80 pounds profit.
This averages out at 4 - 6 pounds per day.
If this is your second field, there is a -25% penalty imposed on your yield. So the numbers for a second field look like this:
If you employ your workers at 0 stats, you will normally get 6 wheat bags.
If you employ your workers at 20 stats, you will normally get 7 wheat bags.
0 stats : (6x13.20)-(16x3)=31.20 pounds profit.
20 stats : (7x13.20)-(20x3)=44.40 pounds profit.
Which averages out at 3 - 4 pounds per day.
Note: If you have two wheat fields, you can sow both fields with 1 bag of wheat if they are synchronized(cycles match each other)