How many crops can take one farmer at time 10 or 12 or ... less ?

Maybe 6?

6 crops at once or six food, because six crops its like 3 food but 12ve crops is 6

You can get 6 total food (so 12 crops) from each. I have three people assigned to food in Sanctuary and I've got 18 food total, despite having more than that planted.

Mutfriuts are worth1 food each, everything else is worth 0.5.

Ah, ty, that helps out. I was having a hard time figuring out why they weren't always working on 12 plants.

12 crops.

or 6 food.