Alfalfa: Encyclopedia II - Alfalfa - Culture

Alfalfa - Culture

Alfalfa can be sown spring or fall, and does best on well-drained soils with a neutral pH of 6.8-7.5. Alfalfa requires a great deal of potash; soils low in fertility should be fertilized with manure or a chemical fertilizer. Usually a seeding rate of 13 - 17 kg/hectare (12 - 15 lb/acre) in climatic acceptable regions and a rate of 22 kg/hectare (20 lb/acre) in southern regions is used. A nurse crop is often used, particularly for spring plantings, to reduce weed problems. Herbicides are sometimes used instead.

In most climates, alfalfa is cut three or four times a year. Total yields are typically around 1 tonne/hectare (4 ton/acre) but vary regionally and with weather, and with stage of maturity when cut. Later cuttings improve yield but reduce nutritional content.

The potatoe leafhopper can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest. Chemical controls are sometimes used to prevent this. Alfalfa is also susceptible to Texas Root Rot. Medicago species are also eaten by the larvae of some Lepidoptera species including Common Swift, The Flame, Latticed Heath, Lime-speck Pug, The Nutmeg, Setaceous Hebrew Character and Turnip Moth.

Alfalfa seed production requires cultured pollinators to be provided for the fields when in bloom. Alfalfa pollination is somewhat problematic in that the keel of the flower trips to help pollen transfer to the foraging bee, striking them in the head. Honeybees apparently do not like being struck, and often learn to defeat this action by drawing nectar from the side of the flower, thus pollination is not accomplished. The majority of the pollination is accomplished by young bees that have not yet learned the trick of robbing the flower without tripping it. When honeybees are used for pollination, the beehives are stocked at a very high rate to maximize the number of young bees. Today the ground nesting alfalfa leafcutter bees, are increasingly used to circumvent this problem. It is cultured in special beds near the seed fields. It is not a complete substitute however as these bees also have their own problems. They are not portable like honeybees; they take several seasons to build up, when fields are planted in new areas. Honeybees are still trucked to many of the fields at bloom time.

Adapted from the Wikipedia article "Culture", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki