New Berries show up when the new crops show up. If you don't collect the crops in between new crops then your maximum is 800. If you get the food to the bin then you will have those crops plus the new 800. If you just wait until your bin is empty to collect the food, you could starve. You want to build up a reserve, especially if you leave the game on when you exit. Plus your villagers don't always eat enough. You also want to teach them to eat, because they can half starve with a full bin of food because, they don't eat enough when you are away. If you work them too hard and their health goes down but they are not officially sick you can bet them up to full health slowly by forcing them to eat drink water and swim in the lagoon. You can set them on nature walks to keep them from moving the boulder while your healthy villagers are in a time crunch. If you put a check by their name to learn a specific career while you are away they will get sick faster. I think it's about the whole free will concept. Now if you check a certain skill, make sure to check their health regular. If you have already taught them to eat and drink a lot, they don't get as sick even if you check the box.

But, watering the crops helps about as much as rain dancing. It does get them into the middle of the field on their own and you can nab them and dunk them in the berry bush. If you let them keep watering the crops they will water the crops 2 minute after the new crops and not even bother to harvest them. So you have to stop them from watering all the time, because they will contribute less for other things.
I think the crops would grow faster if we could use the pond water.

Also about the Farmers. The quickest way to increase levels is to get them to have improved skills. On their own like watering, is a slow process. Fishing is slow. In order to get the farmers levels up the quickest is to make them plant crops when there are none. It's the shortest skill because it doesn't have all that traveling. Also, they are closer to the food bin. They learn faster when they aren't hungry. So if you feed them while they are in training they learn to eat on their own and get sick less. Master Farmers are real stubborn and will act like they can't do other things.