There are many kinds of crops, agronomic crops, feed crops, fuel crops, vegetable crops, and more.
Agronomic crops are typically grown for grain to feed people and livestock, or are processed into products, such as oil, starch, protein, and flour. Major agronomic crops in the United States include corn (grown for animal feed, ethanol, and processing), soybeans, wheat, hay (alfalfa, and legume and grass mixtures), rice, peanuts, and cotton.
Feed crops are grown specifically to meet the nutritional needs of livestock. They include “small grains” such as wheat, oats, barley, and rice, as well as taller grain crops like corn and sorghum.
In contrast to grain crops, alfalfa and other forage crops are grown for their stems, leaves, and other edible plant parts. Livestock either graze these crops in fields or eat stored forages. Stored forms include:
- Hay crops are cut while still green, allowed to dry in the field, and then processed and stored before being fed to livestock.
- Silage crops are harvested in a green, succulent condition and then stored under oxygen-deprived conditions, where controlled fermentation breaks down plant sugars to organic acids, especially lactic acid.
- Green chop is cut, harvested, and fed to livestock while still green and wet.
Fuel or Energy crops are harvested for processing into bio-fuels, such as ethanol and biodiesel, which are being developed as alternatives to fossil fuels.
- Sugar-based bio-fuels, such as ethanol, are made from the fermentation of plant sugars. Major sources of these sugars include sugar cane (grown widely in Brazil) and corn grain (United States). Other sources include wheat, barley, rice, grain sorghum and sweet sorghum, as well as sugar beets.
- Cellulosic bio-fuels: Much research is being conducted today on ways to make bio-fuels from fibrous, or cellulosic, plant materials such as corn stalks, hay, and wood pulp. These materials contain large amounts of a complex plant molecule called cellulose, which can be broken down into sugar and then fermented to ethanol.
- Biodiesel, in contrast, is commonly produced from vegetable oil, making any plant that produces oil a potential source of energy. Common sources of biodiesel include rapeseed, sunflower, soybean, and palm; others are peanut and camelina. Peanut oil was actually the first biodiesel burned in Adolf Diesel’s new engine in 1913.
Many people envision that vegetable crops are grown on small farms, for farmers markets. In reality, most vegetables are grown on large, specialized farms with many custom-designed pieces of machinery to help ease the labor. Many fields may cover hundreds of acres, and farms may be spread over several states to help insure a steady supply of fresh produce to the market.
In the United States, major vegetable crops include lettuce, peppers, tomatoes, squash, sweet corn, green beans and watermelon (watermelon is included here as it is grown like a row crop, on the ground). American Society of Agronomy/2013
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