We were doing quite a bit of oats around here a few years back, the straw after combining was no trouble to bale, I raked some of it to make windrows for the baler, both round and small squares. The straw has a shiny and slippery surface, one mistake we made was with the JD round baler, an '08 vintage, sileage special, we were using net wrap, and when it was processed, I believe the extra knives or other set were employed it made the stalks much smaller, and those bales were a pain to handle, very delicate. The customer it was sold to was a huge dairy, they were grinding it or putting it into the big mixer for roughage. One of the years the field that was planted in oats on our land here, more nitrogen was added and the stalks were noticeable taller, chest high, that increased the straw tonnage by 50%, but it seems with that comes one drawback, about a week before you turn the key to start the combine some of it would lay down, say after a thunderstorm or something, can't say I've seen it flattened, but that picture perfect field you saw just before, is not so perfect. We put guard extensions on the grain head, they're spring loaded, I thought they worked quite well, as we did not really lose any significant amount of grain, thats not to say it could have been worse, but it seemed to work out well.
I'm not sure as to the official way to check the moisture, (moisture meter ?) but once that field starts to tan, it won't be long. Oats sowed in late March, early April, typically are ready to harvest in July, sometimes late July, early August depending on the weather. You can pull off some grain, take the hulls off check by hand, we had no trouble with grain moisture content that I can recall.
Small squares of oat straw as well as the round bales sold quickly and brought more than hay did, it was a good crop. I know oats like nitrogen, I'm not sure what the rotation is, or whats the best practice to keep nutrients in the soil so it grows well, seems to me you could deplete the soils in a few years. I liked the crop because you harvest when there is a much better chance of drier weather, its warm out and you are not fighting saturated fields like it can be with corn around here, all of it sold immediately, so the farmer I helped with this got his return and profit in a timely fashion. Very little hand work, the small bales sold off the wagons, one guy was taking the wagons and returning them empty. I think the worst of it was when the NH 315 baler ran through some bad twine, what a pain that was, and of course it was in the best field of oats, really nice grain and straw, I had some nice photos of that on a phone that got wet, not sure if I have any others of that field.