We are going to be bring the horses home in a few weeks. There will be two in the pasture. We are going to rotate them between two areas, each 100x500. The area used to be horse pasture about 7-8 years ago. And was let grow wild up until we bought it last fall. It was brush hogged around November. Now that spring is here and the horses are coming I was wondering if there is anything I should add to it, as far as seed is concerned. Looked like wild field last fall. After it was hogged, looks like a descent amount of field grass is there and ready to come up now this spring.
A good, healthy stand of grass will outcompete weeds over time. Mow the field when before the weeds go to seed to prevent reseeding them. Also, mowing encourages growth in the grass.
I'd let it go for a year and see what mowing and grazing does for it, then maybe fall seed if you think it needs it.
I would try and burn it off if you had that much dead growth. It's going to be hard for new seed to come up. If you can't burn then I would get a good harrow and harrow the ground up really good. Then I would fertilize. As soon as everything is up I would spary with 2-4D. This will kill your weeds and give your grass a good chance to get going. Once your grass gets going you will be able to see what kinds you have. I would do a soil sample and get the soil right by fall. This fall I would interseed with whatever your pasture is lacking.
Not much fertilizer will hurt horses as it will just be absorbed into the ground for the most part. Get a soil sample and take it to your local farm co-op and they will get you the right mix for your pasture.