A great looking field! Looks like nice black dirt, maybe a few of those rocks could be hand picked off the top. I see ferns growing, is your soil a little acidic? You could try spreading some small grain seed now then do throw n mow in late summer. Check what grows well in your area and then go to the feed mill and get a hundred lb bag, such as buckwheat, rye, oats, barley, or wheat. A cheap cover crop! Your local ag extension agent can also be a good source of information on grain species for establishment and soil building. The thing with soils is that the crop that works best for me in Pennsylvania may not work very well in your dirt in Maine. Even if your soil is too rocky to till it would still be well worth the twenty dollars for a soil test, you save way more money on fertilizer by knowing exactly what you need. If it were my field I'd pick rocks, spray, and notill drill buckwheat, oats and millet combo into it yesterday. Whatever you do, keep something green growing in it all the time, even if its only what's there now. Don't spray it dead in the middle of summer when you can't get anything else established.