what is fertilizer for?
I'm still testing the farming aspect of the game but this is what I found out until now:
First you need to go to a cereal crop field, there you will find weed which you want to dig. The weed becomes weeded soil, now you can fertilize it and it becomes soil.
Weed will grow back on weeded soil, but it won't on soil
If you get cereal from a cereal crop the ground will turn into either weeded soil (not fertilized) or back to soil (fertilized).
Found out that there's no differents in planting cereal seeds in weed, weeded soil or soil, only the hight of the cereal crop varies, which doens't effect the amount that you get from it.
You get 2 cereal seeds from 1 cereal in the cereal seeder (I think the cereal seeder is a little bit to slow for getting only 2, maybe it's just the crude version of it).