Absolutely a good idea!!! I do it with all my chicks and have for years! I dig up a clump...roots, grasses (dead or not), bugs, weeds and all - and put it grass side down in the brooder. I did this with my first, and only, batch of chicks that were raised inside, and I still do it for my chicks that are now raised outside. They climb on it, they dig and scratch in it, they peck at it and ingest tiny bits of chick-sized grit, and as it breaks down they dust bathe in it. They fly up on top, they play King of the Mountain, and it’s a fantastic boredom buster! They are learning to be chickens! In the process they are being exposed to the pathogens, bacteria, and fungi that are present in the environment that they’ll soon be living in while they still have some immunities from their moms. I have yet to have Coccidiosis sweep through my flock, and I’m 6 years and 9 batches of chicks into this!
As for the grit. With my first batch I waited the recommended time (and that varied widely from advisor to advisor so I had to just pick one and go with it) and then I put grit in a small bowl. They absolutely gorged on it. I thought, “This can’t be good!” Then my mentor,
@Beekissed, reminded me that they didn’t need it...the sod I’d put down was all they needed. The gizzard is a muscle. Muscles need to be used in order to develop. So that small amount of grit they get from the sod is perfect for that. Now, I don’t know if it’s coincidence or not, but not once in all the chicks and chickens I’ve raised, has any one of them had crop issues. Not one. (Watch, now that I’ve proclaimed that I’ll go out there and have a chicken with a bad crop problem....<sigh>....my luck!). But a mother hen would have them out there digging in the dirt, eating chicken poop, and ingesting tiny bits of sand and rock at just a couple of days old.
My belief is that if a two pound hen can successfully raise a batch of chicks without heat lamps, books, experts, age charts, and web sites, why do we do it so differently and think we’re doing it better? So I just try to follow what a broody hen does as exactly as humanly possible and it’s been pretty doggone fantastic for me! Toss that clump of sod in there! At first they’ll be terrified of this alien being coming to devour them. Be patient. Eventually one or two will inch over and start messing with it. After awhile they‘ll be all over it! Good luck!