Yields, weeds and pests
Yellow fields in the spring are a tell-tale sign: More and more farmers in Germany are turning to oilseed rape. In the last fifteen years the area under cultivation has doubled, reaching 1.43 million hectares in 2005. The main reason for this is the soaring demand for rape oil, which is profiting from the biodiesel boom. However, quite a significant agricultural outlay is required to obtain good yields.
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Cultivation: With a market share of approximately 40 percent, Germany is the largest oilseed rape producer in Europe. Rape is an attractive alternative to sugar beet, particularly for arable farms in the new federal states. Mecklenburg-Western Pomerania and Saxony-Anhalt are the main areas of rape cultivation. Rape oil for the food industry is produced on approximately 28% (400,000 hectares) of the rape cultivation area in Germany. 100,000 hectares (7 percent) supply raw materials for oleochemicals and lubricants; the remaining area (65 percent) is used to produce biogenic fuels. Yields: Modern rape varieties produce excellent cooking oil with average seed yields of 3.5 tonnes per hectare. This corresponds to 1,400 litres of rape oil. Farmers in Germany, Britain and France obtain the best yields per hectare. Global production: Rape accounts for approximately 10 percent of global oil-seed production, taking second place behind soya beans (60 percent). China and Europe are the main rape-growing regions in the world. They produce two-thirds of the global harvest. Winter and summer rape: Winter rape is mainly grown in Central Europe. Sowing takes place in autumn and it is harvested early the following summer. In Canada, the leading rape-producing country in the world, summer rape is more widely grown. Crop rotation: In Germany oilseed rape is often grown in rotation with maize and winter barley. Without crop rotation pests and weeds would increase significantly, and yields would fall. Crop intervals must be observed: since rape is a host plant for soil-dwelling pests and pathogens, it should not be grown in successive years. A four-year crop interval is required when growing rape in rotation with cereal crops. Soil fertility: Rape improves the fertility of the soil. The long growing season ensures that the soil is covered for eleven months of the year. This reduces soil erosion. |
Weed control: Various plant species compete with rape on arable land and emerge as weeds. Typical weeds in winter rape include cleavers, chickweed, camomile and black grass. "Volunteer cereal plants" can also be a problem, especially barley, which is grown in rotation with rape. In conventional rape cultivation weeds are controlled with chemical herbicides.
Herbicides: Chemical weed control is used on virtually the entire area under winter rape cultivation in Germany. It is standard practice to spray once or twice using at least two or three different active ingredients. Herbicides are applied at the time of sowing, shortly after sowing or shortly after the emergence of the rape seedlings. Rape-tolerant active ingredients for subsequent control of weeds in the rape crop are only available on a very restricted basis.
Pests: Typical oilseed rape pests include cabbage stem flea beetles and field slugs in autumn and rape blossom beetles and rape stem weevils in spring. Increased fungal infection can also occur when the stems split open in severe frosts. Diseases caused by fungi in rape include stem and crown canker. As a result of heavy yield losses and reductions in quality, insecticides and fungicides are normally required to control pests and fungal diseases.
Harvest: Harvesting takes place at the end of July/beginning of August, using a combine harvester. Oilseed rape is ready to harvest when the seeds are hard, dark brown to black and rattle in the pods when the plants are shaken. At this stage the rape straw may still be partly green. The harvested rape seeds are dried, because a maximum water content of nine percent is required for storage.
Organic oilseed rape cultivation: Very little organic winter rape is grown. Since no chemical crop protection products may be used, high weed and pest pressure results in yield levels of approximately half that found in conventional cultivation. Although the cultivation problems associated with summer rape are less serious than with winter rape, an increase in organic rape growing is not likely in the future. (Proportion of rape-growing area in Germany: approx. 0.3%)
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