Whoa, VillageIdiot... That's a lot of food.

I have 12 villagers (8 adults 4 kids), and i have 3 people on research and 5 on farming, and the food goes up to 400 about, but as soon as the crop dies and they have to water the field for a new crop, the food drops down as low as 50... Then the crop grows and it rises to about 350-400, and the cycle starts again.

Am I doing something wrong? I'm at Level 2 everything except for Medicine and Fertility. And I haven't had any floods to wash the food away, or anything like that. I'd love to keep a minimum of 300 in my bin, but I don't know how.