hay baler, farm machine that packs and ties (or wraps in plastic) field-dried hay into bundles, called bales, for convenient handling, storage, and shipping. It ordinarily picks up hay that has been raked into rows (see rake)and packs and ties it into round or rectangular bales to be picked up by truck. Some modern balers include automatic stacking or loading devices. Very large bales are often stored in the field and moved with front-end loaders. Nearly all hay in the United States is baled.
See C. Culpin, Farm Machinery (12th ed. 1992).