Ahhh... I'm sure you are right. It is how I read the descriptions.
Level 2 gain +1 additional from crops
Level 3 gain +2 additional from crops
Level 4 gain +3 additional from crops
Level 5 gain +3 additional from crops
I equated that to, at the minimum, +9 additional from crops but based on what you said it is non-stacking.
Thanks for the help.