ON a sunny Sunday just before the vernal equinox, Rich Ciotola set out to clear a pasture strewn with fallen wood. The just-thawed field was spongy, with grass sprouting under tangled branches. Late March and early April are farm-prep time here in the Berkshires, time to gear up for the growing season. But while many farms were oiling and gassing up tractors, Mr. Ciotola was setting out to prepare a pasture using a tool so old it seems almost revolutionary: a team of oxen. more