Join Date: May 2009
Location: Mid Northern TN
If you don't know who farms that field, do you know ANY farmers? They probably know who does every acre in the county. If you don't know any of them, talk to the folks at your local feed and farm supply store- you might have to talk to a manager, but they DEFINITELY know at least a few of the local farmers, and they could help put you in touch with one or two so you can track down who farms the fields by your pasture.
Without knowing WHAT chemicals are being used, it is completely impossible to know or even guess if your horses will be safe. Some chemicals are safe after they dry. Some need to be rained on before they're safe. Some have a time limit before they're safe- maybe two days, maybe two weeks, maybe a month. The only way you're going to know is to track down the farmer and talk to him. Short of that, you're just putting them out there and hoping they don't get accidentally poisoned.