The word "rape" as applied to oilseed crops is derived from the Latin word rapum that means turnip. 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 commonly 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. At present around 400,000 hectares of oil seed rape is grown annually throughout the UK, roughly one eighth of the area of wheat and barley. Most of this crop is sown in the autumn after the cereals harvest and is known as winter oilseed rape Oilseed rape is not a very high yielding crop by comparison with cereals. A typical yield for winter rape is 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.