A BASF calculator?

On my (almost) daily hike through the (often cultivated) nature of the Odenwald I stumbled over a little green calculator at the side of the dirt path.
Not only the place to dispose of a pocket calculator, also the names printed on it did make me wonder. BASF and Zampro. Quote: "Zampro® fungicide is the latest fungicide for leafy vegetables, cucurbits and a variety of other vegetables."
The calculator might have been issued by BASF to help the farmers with calculating the seeding rate. I don't think the purpose was to make good farmland into garbage-land.
Thanks to Marlieske for hosting the Derelict Sunday challenge.