Oats make a nice nurse crop for other plants, particularly if you plant them in the fall and let them winter kill. They don't fix nitrogen, even when inoculated with an appropriate bacterial inoculant.
http://covercrops.cals.cornell.edu/late-summer-legumes.php
As was stated above, you can crimp oats at the base and that will stop them from growing. On a large scale, a roller or crimper is pulled behind a
tractor and flattens the oats all in the same direction, laying down a thick mat of mulch. On a small scale, using a scythe or just a pair of hedge clippers will cut the oats off at the base and drop the plant to the ground as a mulch. If you've got
chickens, then you can run them through and they'll go crazy for those oats.
Here's a great article on cover cropping, including using oats:
https://www.uvm.edu/vtvegandberry/factsheets/covercrops.html
I use cayuse oats as a part of my winter/cool season cover crop mix, along with hairy vetch, purple vetch, buckwheat, bell beans and tansy. It comes up in a big tangled mess -- all the better to feed the soil and provide winter habitat for my spiders, lizards, and other garden dwellers. By March, it'll be 4 to 5 feet tall—the great green biomass wall. I take the scythe (or my electric hedge trimmer) and knock the whole thing back in preparation for spring planting. Another benefit of growing a winter cover crop is that it keeps the temperature of the soil down so my stone fruit
trees don't break dormancy too early.
Everyone
should make a couple of mistake every year in order to learn something new. But those oats, sew them, and see what happens. If it's a flop, you'll learn, you aren't out too much money. It it's a hit, you'll learn and your garden will be all the better for it. Give it a shot. Tell us what happens.