agricultural experiment station agricultural history of the united states agriculture alfalfa almond american civil war apple barley bean beef beef cattle beekeeping cattle center pivot irrigation chicken cotton cottonseed oil dairy dairy cattle fruit goat grape great depression greenhouse habitat destruction hay hops horse kansas land-grant university lettuce maize melon mentha milk oat pea peanut pig plantation popcorn potato poultry rice silage sorghum soybean sugar beet sugarcane sunflower sweet potato tobacco tomato turkey united states united states department of agriculture vegetable wheat wikimedia commons