will my chickens get enough grit from the yard that I don't need to provide it to them? They are about 9 weeks old and in the yard all day long
If they are on the ground that should be enough. I've never fed grit to my birds in the hen yard or tractors and they eat whole corn every day.
It does depend on the type of soil you have, and if it has small rocks that are hard enough to work as grit. In some areas it would be worth it to buy a bag of grit every once in a while. It's pretty cheap and they don't eat that much.