i would heartily second the rotational pasturing. it's something we are working on at the moment, but with 50 horses and 20 cows it's a bit of a headache. for the past several years, our pastures have been completely abused by my extremely short-sighted aunt (by marriage) who couldn't care less when we have to purchase hay in the winter and are starting to have erosion problems (she's runs the equestrian school and has been given a lot of unnecessary free reign in matters she doesn't understand).
what you want to think about with grass is it's optimal growth time (see page three of
this article). that will change over the seasons, but in early spring it's around 14 days. ideally then, each blade of grass would be cut (mowed or eaten) every 14 days.
optimal growth:
day 1: the blade of grass is cut. grass balances it blade and it's roots, so the plant kills off most of the roots, which then become food for the organisms in the soil and make GREAT fertilizer.
days 2 & 3: nothing should be allowed on the grass during these days. the grass will immediately begin rebuilding the blade and the roots.
day 4: if you have chickens, you can run them on the grass on this day. the short grass is easier for them to eat than larger blades and they will decimate the horse/cow poop. this will basically rid your paddocks of parasites AND spread the ruminant poop around nicely, fertilizing the field even more and spreading any seeds in it. plus, the chicken poop will help fix nitrogen in the soil.
days 5-13: nothing should be allowed on the grass during these days. the grass will grow rapidly, sending out new roots.
day 14/ day 1: this the the last day of optimal growth. after this day, the blades will begin to get woody (less appetizing and digestible) and the weeds will go to seed. this is the day you want to reintroduce the horses or mow the grass. the cycle will start over and the grass will continually get stronger and the soil will be AMAZING.
as the others were saying, free choice grazing is terrible on paddocks as the good grasses get decimated before they can reach their optimal growth and weeds get left alone to take over.
here's what you could do:
1. invest in some movable electric fencing (you could go with 1 or 2 strands of hotwire probably). depending on your paddock set up and your access to electricity, you might need to splurge on a solar fence charger or just a couple car batteries (these can power a regular fence charger for at least a day and you can recharge them).
2. you want to break the paddock into a rotational grid. you are aiming for sections that are just large enough to be grazed pretty completely in a single day. ideally, you would have 13 sections that they would rotate through in a continual pattern, but that may not work out. it'll take some trial and error to figure out the right size/rotation but it'll be a great big help in the end. you could perhaps divide the field into this management-intensive grazing section and then whatever is left you could do some of the other suggestions about manure spreading.
3. you want to move the horses onto fresh pasture at the end of every day. this way the freshly grazed section is protected from those heavy hooves while it is vulnerable. you simply set up the next section with the electric fencing (which shouldn't take too long), let the horses onto the fresh grass, supply some water, and you're done!
like everything else that is good for us and our land, this is a major chore at first. once you get the right rotations figured out though, it's pretty easy and well worth it.
I did put up some gorgeous hay, but had to drag it into the barn on a tarp. I'd like to build a stack one day, right in the field. Or a shed to stuff the hay into. Maybe a pallet shed....
