Oats are the third most important cereal crop in the United States, according to the Purdue University Extension, grown in each state of the continental U.S. and in Hawaii. Oats are primarily used as a food crop and livestock feed but have recently gained importance in organic and sustainable agriculture as a green manure cover crop. Oat protein is nearly equal in quality to soybean protein.
An early wild ancestor of the domesticated oat plant was known as Avena sterilis. It grew in the Middle East and began to be cultivated in the Bronze Age. Oats also appeared as a domesticated cereal crop in Europe at this time. Wheat and barley were considered the primary cereal crops and oats a secondary crop. They have spread to all temperate climates of the world, where they are more tolerant of cool, wet summers than other cereal crops.
Oats are an upright, annual grass that reaches a height of 2 to 5 feet, adapting to fall planting and mid-summer harvest or spring planting and late summer harvest. It is grown for its seed, used as a cereal product and livestock feed. Oats are also grown as a cover crop to enhance soil fertility with its nitrogen input. It has a fibrous root system that increases soil friability when left in the ground after harvest.
Oats begin their growth cycle as a shortened stem with leaves growing in a rosette pattern. It may be upright, semi-prostate or lying horizontal to the ground. Branch buds may develop under ground, break through and form additional branch plants or "tillers." Up to 30 tillers may form on fall-planted oats, with considerably fewer on spring-planted oats. In spring, the rosette-shaped plant grows to 2 feet or more.
When oats reach 2 to 5 feet, they develop a panicle on which flowers and seeds develop. It is large and loose in shape. The panicle has a central stem and side stems called rachis. Each rachis terminates in a spikelet that rises in whorls at the nodes of branch stems. From 20 to 150 spikelets develop on each panicle, dropping downward or remaining upright. Each spikelet produces two oat kernels, or seeds.
Oats are harvested by swathing, which cuts the plant at 4 inches above the ground. In sustainable agricultural methods, oats are used as a green manure cover crop to suppress weeds and improve soil structure. Oats are "very good as a catch crop for taking up and storing excess N (nitrogen) and providing erosion control," according to the University of Hawaii Extension.