Equipment needed for keeping horse pastures and horse arenas trimmed depends on the size of the horse arena and horse pasture, and how many horses and riders use them. Keep tractor size and capabilities in mind when you purchase a new mower, rake or drag for the horse arena and horse pasture. Don't buy implements that are too big for your tractor. You don't want to burn up a small tractor by using it to pull large, heavy implements through tall grass or deep sand.
A 25-45 horsepower tractor works well for smaller operations and can handle most implements up to 5 feet wide. Try to get one with a three-point hitch (for raising and lowering implements) and a live power take-off (PTO), which operates implements with moving parts (mowers, post hole diggers, broadcast spreaders, etc.).
Mow Those Pastures
Most folks probably buy the tractor first, or already have one, and it might have come with a brush mower already attached to it. Most rotary cutting mowers, such as Bush Hog (Bush Hog is a registered trademark name), are single-blade mowers that can flail their way through tough, tall brush. They generally cost around $1,400-$1,600 new, but you can sometimes find a used one.
A brush mower works great in overgrown fields and where rocks or sapling trees are a problem, as the blade is designed to "give" when it hits something instead of breaking. It'll mow nice, flat pastures, too. But it doesn't do a very pretty job.
If you have relatively smooth pastures and want to keep them trimmed and looking nice, you'll get better results with a finishing mower. Finishing mowers have three blades instead of one, so you get a smoother, more uniform cut, and four wheels, so you can adjust the cutting height. They come in various widths and work on a tractor with a three-point hitch and a PTO. They cost more than a Bush Hog-style mower. (A 5-foot finishing mower runs around $2,000.) Choose one with a rear discharge instead of a side discharge and you'll really like the way your pastures look when you're done.
You can't just hit the pastures with a mower once or twice a summer. Depending on the rainfall, you'll want to run over the field with a mower once every two or three weeks. This will keep weeds down and allow new, tender grass (the horses' favorite) to come up. Keeping the pasture mowed encourages horses to graze throughout the field and not just in a few favorite spots, while the rest grows tall and unsightly.