Much depends on how intensely you want to manage the pastures. I would get soil samples as soon as you can dig in the ground. Use a spde to get dirt down where the grass roots grow, from several location of the fields. Send it in for testing, so you know what the land needs, not using a “generalized” formula fertilizer. I get my fertilizer from a fertilizer plant, mixed for my land by my soil test results. Ask some local folks where they get farm fertilizer, if there is no obvious place.
Next management tool is going to be dividing your big fields as suggested above. That will give you four grazing areas, approximately the same size to rotate between. I am guessing you have less than a total 5 acres because of house, barn, driveway and lawn. I would be prepared to feed hay at times because with more than 2 animals, you probably won’t have enough grazing room to sustain them on pasture alone.
I fertilize in spring or early fall, no later than 2 weeks after Labor Day. This later time gets fertilizer into the plants, food for winter. Spring gives things a good start to the growing season. Both times are also good for adding seed. I kind of watch the weather after lightly discing fields to open packed soil, then fertilize when rain is predicted in the next day or so. I ALWAYS tell the fertilizer folks I want Amonium Sulphate instead of Urea, as my Nitrogen component in the mix. Urea is bad for horses, so we don’t use it at all. Costs the same, so being safer is the way to go. I keep horses off the fields until fertilizer has been ‘rained in’ so I can’t see any granules on my dirt. I have been fooled by weather predictions, had no rain, so they were dry lotted a week or more!
Then the mowing part. You don’t say where you are, what kind of rainfall you get. A speaker told us that with any grass, mowing high, mowing often, is the key to keep it productive. True for lawns and pastures. I mow when grass is between 8-10 inches tall. Shorten it to 5 inches, which leaves it long enough to feed the plant, not shock the plant badly by cutting it shorter. Length softens rainfall and slows runoff so water goes into the ground. Plants put energy into good root systems for being more productive, instead of being all leaf growth. In spring, this can mean mowing weekly because I don’t have horses on full-time grazing yet. Mow if it looks like grass is setting seed because plant will go dormant once seed is set. No more growth then! I quit mowing about Labor Day, to let grass get long for winter nibbling, soil protection from horses running over it.
As horses are able to graze longer, they need to rotate among the fields. I do not use a time schedule (like change every 2 weeks), but see how the field is growing. Means I have to walk over it, look at the plants. I do not want the grasses getting too short for the reasons above. You also have notice if rain is allowing grass to grow steadily. Small field, 2 horses, you may need to only leave horses on it 4 days, then move them to the next field. Longer grasses come back faster than grazing it way down allows. I mow the field right after taking them off, if not in drought times. Drag as needed to break up poop right after mowing. Mowing cuts weed growth so they can’t reseed, on most taller weeds. In drought times, I quit mowing, rotate horses often. Might be every 2 days with smaller fields. It allows a bit to grow before they come back again. Just don’t want it chewed down to the exposed roots.
I only have horses grazing half the day. They come in day hours to be away from insects, handy to grab for being used. They would be obese with full time grazing! Horses just do not need to be eating 24 hours of a day. They get their grain with wet beet pulp inside, not much or no hay. This half day allows pastures to be less grazed, recover faster, in the rotation between uses. We are HUGE believers in the benefits of grazing, pasture play, so I work hard to keep things productive for our number of horses out there. We are a smaller acreage, probably 11 acres for the 9 horses. So I pay close attention to our pastures and production. Pasture is better forage than hay, with the added benefits of being able to run hard, play, Vit D from sunshine, be in a herd setting for socializing which is mentally healthy. None here have any ‘issues’ needing special treatment, medications. They work hard when asked.
Your County Agent should be helpful on types of seed to plant, buy seed locally and get more than one kind. Local seed does best in YOUR area. No use planting all Bluegrass if you live in a place that is hot. Bluegrass does better in cooler temps, unproductive here in hot July, August, so I would have nothing to graze. A variety will keep something coming on all season with cool and warm season plants. I have clover self-seed from neighboring fields, but regular mowing prevents lush growth, allows daily drying to prevent fungus growth that can cause slobbering. You can also spray it to spot kill.
It is work having good grazing, and I need to maximize what we grow for so many horses. Reward is seeing our shiny performance horses, knowing it came mostly from that excellent pasture.
