Grasses are generally excluded from what I know because most of them (if not all) compete for nutrients and water at the same layer as the feeder roots of most fruittrees. Also because they are aggressive at shading and/or choking out other herbaceous plants. , If you're looking for a grass for the system...bunching grasses aren't too bad at aggressively spreading and casting too much shade in my experience but I'd still suggest avoiding grass altogether.
guess it depends on the SIZE of your property..and what you are growing..I have a fairly large group of gardens on our property, and there are some grasses grown here..
I have some ornamental grasses here and there among the gardens and I use the spring cuttings as a sort of hay mulch..and I have a very invasive grass called ribbon grass that grows down a couple of my banks, i tend to love it but most people probably don't. I wouldn't recommend it near any crops that it might take over or food crops though..
I have grass / lawn paths through my food forest gardens as a trail..that is mowed..and the paths are mostly edged with a plastic edging or wooden bed border to keep the lawn/path grasses out of the beds themselves..i do NOT use any sprays or chemicals on those grasses.
there are also crop grasses such as corn and some grains..they are also useful..I am growing small patches..not acerage..of food grasses and other grains..here, but they are separate somewhat from the food forest gardens..I have a patch of oats and a patch of barley, both hulless, that are growing on the south edge of my aspen woods where it opens to a bank north of my pond, and haven't yet planted my corn, which is a grass, which will be in it's own patch as well away from the food forest..so it can have wind to pollinate it..I will be planting winter wheat in the food forest garden after the summer crops have been harvested as it will grow in the fallow soil ..you could also use a rye for the same thing..
so yeah, some of us still use grasses.
Bloom where you are planted.
we grow perennial bunching grasses for cut and repeat mulch, the benefit is this mulch is guaranteed foreign (weed) seedfree because its just grass leaves. these grass leaves are also a bit tougher than most lawn grasses or grain grasses and sticks around longer as a mulch.
the roots grow deeper accumulating nutrients that are lost from the topsoil layer, similar to comfrey.
they also provide nice microclimates between the various bunching grasses.
The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human beings. - Masanobu Fukuoka