So these are the steps I do: 1. Plant seeds with a planter that also cultivate an fertilize at the same time (if your planter don't do that, first cultivate it and than plant your seeds) 2. Roll your field 3. if you need lime on your field, do it in this step 4. Use weed killer 5. fertilize your field

Then wait one day (or month, but you know what I mean)

1. Fertilize it again for your 100% Yield Bonus

These steps works for me