The correct acreage per horse changes with the season as well as with other factors. However, a good rule is to provide at least one acre of good quality pasture per horse. Then set up 5 or 6 paddocks, letting the horses graze first in one area for about one week and then change to another. This system helps to keep the legumes and grasses growing better and increases the feed available per acre. In addition, by rotating the horses from pasture to pasture you can break the life cycle of some parasites.
Clip pastures regularly during the growing season.
Clipping at a height of 2 to 3 inches after horses are moved to a new paddock helps to control weeds, prevent grasses from heading and in general keeps the pasture in a more desirable condition. Drag pastures with a chain link harrow at least once per year. Dragging helps to spread manure droppings which reduces the parasite populations by exposing them to air and sunlight. Dragging also helps to smooth over areas dug up by horses' hoofs on wet soil. Apply fertilizer as needed.