Mechanized systems of food and fiber production used in agriculture. These systems extend from initial tillage of the soil through planting, cultural practices during the growing season, protection from pests, harvesting, conditioning, livestock feeding, and delivery for processing. The trend has been to larger self-propelled special-purpose machines, except for tillage where the trend has been to large four-, six-, or eight-wheel or crawler tractors used in conjunction with high-capacity plows, disks, and deep rippers.