It depends on the crop.
Corn (Maize): Harvested using combine harvesters that pick, husk, and shell the grain. Sweet Corn might be the exception.
Soybeans: Harvested using combines to cut and thresh the plants.
Wheat, Barley, and Oats: Harvested using combines to cut, thresh, and clean the grain.
Cotton: Harvested mechanically using cotton pickers or strippers.
Rice: Mechanically harvested with combines when the stalks are dry.
Potatoes and Root Vegetables: Lifted from the ground using mechanical harvesters that separate soil from the produce.
Lettuce, Spinach, and Celery: Mostly hand-harvested by crews, though automation is increasing.
Berries (Strawberries, Blueberries): Primarily hand-picked for fresh market quality, though some are machine-harvested for processing.
Tree Fruits (Apples, Cherries): Mostly hand-picked to prevent bruising, though some processing cherries use tree shakers.
Wine Grapes: Frequently harvested by hand to ensure quality, especially for high-end wines.
Peppers and Tomatoes: Processed tomatoes are machine-harvested, while fresh peppers are largely hand-picked.