There is a wide variety of specialty crops including, but not limited to, alfalfa. It is also common for the seed crop to be rotated with a cover crop in order to replenish soil nutrients and help control pests. Alfalfa's ability to fix atmospheric nitrogen makes it valuable as a rotational crop and cover crop, especially in organic farming systems where synthetic fertilizers are avoided.
Alfalfa is an herbaceous perennial plant grown worldwide as fodder for livestock or for supplemental irrigation by farmers. In the U.S., alfalfa was worth $1 billion annually before 1959 when production declined from 75 million tons per year (to about 20 million tons) because of disease outbreaks (e.g. alfalfa mosaic and purple rust). Now it is worth $3 billion annually. It has been estimated that one ton of alfalfa is processed into twenty two and a half pounds of milk, or sixteen pounds of meat.
Alfalfa is a relatively easy crop to grow and is used for forage, hay or silage, seed, and as a green manure crop. It can be grown as either a winter or summer crop in most temperate climates, but not in the tropics (due to its intolerance of hot weather during its growth period) or in areas with extreme winters because it requires cold weather to break its dormancy. It grows well in many types of soil, but it does require good drainage.
The most important use is for livestock feed, accounting for 75% of world alfalfa production (and 70% of the value). Poultry and dairy farmers commonly feed alfalfa to their animals. Alfalfa can be harvested by mowing or swathing. In some areas, scything is used to harvest alfalfa at a particular stage in its development while it is still soft. This is known as "eyrie" cutting or "budding".
Alfalfa is often used for pastures and hay crops, but alfalfa is not a grass. Instead it is a legume that looks like a short shrubby tree. It can make use of nitrogen from the atmosphere to form usable forms of nitrogen in the soil. The leaves are about two inches long and have small jagged edges. In the springtime, new leaves are reddish purple on top with silver white undersides. New flower heads develop each day from April to October or later if it rains enough. The flowers grow on stalks. Four to eight reddish purple flowers surround a cone-shaped head.
There are different varieties of alfalfa, some perennial and some annual. It is commonly used for forage and hay. Alfalfa can be grown in many different ways: seeded, drilled, broadcast, or transplanted from plugs or from crowns. It can be used for hay feeding or pasture grazing depending on the variety selected, but it grows best when it is provided ample nutrients and water in the early stages of development. The top growth can be harvested as hay for animal feed or dried and baled for other uses. The stalks left after harvest can be used as a source of hay for later use. There are many ways to harvest alfalfa but the most common is to cut it in the early morning when the dew has evaporated and before the heat of the sun.
Alfalfa is related to clover and to many other legumes such as peas, beans, soybeans and peanuts. It has been grown for thousands of years in central Asia, Greece and Egypt. Forty years ago alfalfa was brought to North America. Alfalfa was considered a poor man's crop because its roots were used as a vegetable during times of famine in Europe from 1200 AD through 1500 AD.