I've been crunching some numbers about guano. I don't have Croppery 3 but I don't think it would make much of a difference as super harvests don't happen often enough.
With Croppery I, 1 Tomato Seed (20 currant) grows to 14 tomatoes (70 currant). If you were to feed a piggy (3 tomatoes) and grow 2 guano (6 tomatoes), it would be 9 (45 currant) tomatoes lost. You would end up with 5 extra tomatoes. 5 tomatoes are left BUT you lost 9 tomatoes (45 currant) and the seed costs 20 currants. So you only gained 1 tomato (5 currants).
EDIT: Corrected some of my math again. Wow, I was totally off.