With two horses on ten acres, your poo will not accumulate in vast quantities. Two on less than three acres have provided us with a very managable compost pile. With a 10-acre field, rather than pick it up, you'd probably do just as well to pick up the potty zones and rake in the rest. What gets picked out of the stalls can go in a compost pile. A well managed pile can compost down in as little as 3-4 months, at which point it can be added to a garden, flower beds, spread in the pasture, or given away.
The bigger issue is flies, but the more diligent you are about managing the poop, the fewer flies you'll have to deal with.
"I did know once, only I've sort of forgotten." - Winnie the Pooh
I have anywhere from 2-5 horses on 11 acres. Horses are out 24/7 with stall access in bad weather. There is a 1/2 acre dirt sacrifice paddock where they spend the night (and days when they're not on grass) that I pick clean daily--horses all poop in one corner (bless them) so this is not a huge job. Grass paddocks are harrowed about once a month or so to break up piles.
All poop and bedding is dumped into two hand-built (by me) composting "bunkers" that are about 6 x 6 feet, standing side by side. Quite regularly, I turn the piles with my loader to get the composting process started, add water if it's dry now and then, and when one of the bins is full I haul the half-cooked stuff down about 500 feet from the barn in a convenient corner of the property for finishing and where people can easily come pick it up and haul it away. I advertise it on Freecycle and Craigs List spring and fall and usually have all of it gone within a few weeks. I spread a little, use some in my garden also.
Choice of bedding is very important--for me, pelleted bedding or very, very fine screened shavings compost the quickest. I loathe straw and big shavings and won't use them. Pellets are the best (IME) for composting but soaking them is a pain in the winter. Ultra-fine shavings are a very close second and more convenient/quick. My horses only sleep in their stalls in the vilest weather and then only for a few hours, so bedding is not the largest part of my muck pile. In fact, if the pile is getting a little heavy on poop, I'll chuck a bag of shavings in and mix to keep the ratio of carbon:nitrogen optimal. (see above link)
Well, not a very small nutshell . . . I am obsessive about my manure pile and my composting system and it is one of the great pleasures of having my own place, oddly enough.
I'd say to invest in a harrow ($500, I think), and just harrow the field periodically. I'd compost the rest . . . I wish I were like Deltawave, but all I do is maybe three times a year move the pile that's near my barn to a more remote location on the farm and let it sit there. Within a year or so it turns into great compost.
I have between 5-6 horses on about 6.5 acres. They are on turnout between 8-16 hours/day, depending on the season. When not on turnout, they have stall/paddock access. I pick the stalls and paddocks mulitiple times daily.I only harrow the one small pasture and the rest I keep mowed to prevent weeds from taking over. I haven't needed to harrow those pastures yet so I haven't.
I have 4 compost boxes, each approximately 8 ft deep and 15 ft wide. The daily manure/bedding goes into the first box until it is filled. I then turn everything from the first box into the second and so on down the line. By the time it has reached the fourth box, it is nice and richly composted. We place ads on Craigs List-I actually charge $10 per pickup/trailer load because we load it with our tractor. So far it has worked really well for us.
I just remade my compost boxes-they are now cinderblock following a plan I got online from Penn State. The information you can get online on composting is awesome. Rutgers University also has some really good info.
Like Deltawave, I'm kind of obsessive and proud of my compost, too. It also grows some really great veggies!!!