Okay, so here is the situation. My partner and I are making a mod for the game (dua) and we got stuck. 
We want to add a means for a player to hit the grass (but not break it) to pick up an item like a small stone.
We have spent hours searching for tutorials or some explanation but with no clear answer so our questions is, how does this work?
Does anyone know of a source that would help explain this or of a tutorial we just have not found yet? Or better yet, help us figure this out so we don't have to spend another 8 hours surfing the web?

1 hour ago, diesieben07 said:

PlayerInteractEvent.LeftClickBlock should do what you want.

Okay, well, great to know but he literally just changed what he wanted over the last minute and wants the player to have a possibility to gain a modded item via breaking grass (plant not block). 
I will note down what you said though. Better to have that in the notes and not know about it. Thank you for that. 

1 hour ago, diesieben07 said:

To change the drops for a block use BlockEvent.HarvestDropsEvent.

Thank you. I will pass this on. Your help is greatly appreciated.