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The word "rape" as applied to oilseed crops is derived from the Latin word rapum that means turnip. Today turnip rapes and the similar but more common swede rapes are grown for their oil and are widely recognised by their bright yellow flowers that can be seen from late April onwards.

The familiar yellow-flowered rapeseed crops have been cultivated throughout much of the world for at least four thousand years, although it was not until the 13th century in Europe that this was done on a commercial scale. At the time its primary use was as a lamp oil but prior to this the oils had been used in soaps and for other purposes.
In 1740 Carl Linnaeus noted that the crop had a useful soil improving role that aided the performance of following crops. This is a role that is still vital today and oilseed rape is known as a "break crop" - one that helps improve the yield of the following cereal crops, in particular wheat.
Despite its useful role as a break crop, oilseed rape cannot be grown too regularly in the same field for the risk of a serious disease build up. Oilseed rape is always grown as part of a farm rotation and rarely returns to the same field more than one year in three. Other important break crops include, potatoes, sugar beet, grass leys, peas and beans all of which allow insects and fungal pests to die out between cereal crops.
In the UK the oilseed rape crop was barely known until the 1970s when the explosion in commodity prices and targeted support from the CAP raised the price to a sufficiently high level that farmers chose to grow it. Now, around 400,000 hectares of oil seed rape is grown annually, roughly one eighth of the area of wheat and barley. Most of this is autumn sown and known as winter oilseed rape.
Oilseed rape is not a very high yielding crop by comparison with cereals. Typically winter rape yields around 3 tonnes per hectare compared with 8 tonnes per hectare for wheat. However, with a higher price and the "break crop" benefit to the following wheat crop, oilseed rape remains an important crop in the arable rotation and currently the UK is about 90% self sufficient.
Today's varieties of oilseed rape have been bred to provide an oil that is suitable for use in cooking and food processing. Known as vegetable oil, the oil is widely used by the food industry and is now being increasingly processed for use as biodiesel.
From ukagriculture.com