Rapeseed is an oleaginous plant widely distributed all around the world. It has the capacity to grow and develop under temperate climate. Rapeseed is adapted to many soils, being the fertile and well-drained soils the more advantageous, as it has low tolerance to floods. The best are loamy soils, composed of clay, silt and sand. The desirable pH is from 5.5 to 7, but it also withstands some alkalinity, up to 8.3. It is resistant to periods of drought due to its deep taproot and the fibrous near-surface root system and has a good recovery after the drought (Sattell et al., 1998). An image of the rapeseed flower is shown in Figure 1.

In the studied zone the rapeseed is a dry farming plant. Thanks to its deep roots, rapeseed can gain access to subterranean water resources better than wheat and barley, grains usually

grown in the area studied. The recommended field rotation for rapeseed is planting every five years in rotation with wheat (1 year) and barley (3 years). If there were strong price expectations, producers might keep rapeseed in the same field for two or even three years at the risk of the crop developing fungal diseases (Provance et al., 2000).

Fig. 1. Image of the flower and siliqua of rape (Photo J. F. Marti).

In order to select the rapeseed variety better adapted to the area of study (Anoia area in Catalonia, Spain, selected as a dry Mediterranean area) a test has been carried out in an experimental and representative field. The yield and the oil content of 9 rapeseed varieties were studied during the harvest of 2006. The experimental field was divided into 36 rectangular divisions, this is to say, 4 replicas of each one of the 9 studied rapeseed varieties were performed.

This study is still being carried out in order to average the results obtained in various years. Table 1 shows the preliminary results obtained in the harvest of 2006. The results obtained in 2008 were unusable because of the hard drought suffered in the autumn of 2007 and the winter of 2007-2008.

Table 1 it seems clear that the rapeseed variety with more oil content is the Pacific, but the varieties with higher yield are Sun and Potomac. Thus, the Sun rapeseed variety maximized the rapeseed oil yield in the study of the harvest of 2006.

As a ground fertilization, the application was 450 kg/ha of a fertilizer of 15% nitrogen, 0 % phosphorus, and 15% potassium oxide. Additionally, 260 kg/ha of ammonium nitrosulphate of 27% nitrogen was spread out as a fertilizer coverage.

Before sowing, an herbicide treatment consistent in Trifluralin (48%, 2.5 l/ha), Glyphosate (36%, 1.0 l/ha) and Metazachlor (50%, 3.5 l/ha) was applied. The insecticide treatment was an application of Deltamethrin 2.5% of 0.4 l/ha.

Rapeseed agricultural production includes the use of different products (fertilizers, pesticides, herbicides, fungicides, rapeseed seed to plant) for its cultivation as long as the agricultural work done (mainly tractor work). Considering the studied region, dry farming conditions for rapeseed are taken into account. The yields in Table 1 are very high because they are obtained from an experimental study, where the edge effect and other variables increase this production value. In this study, the rapeseed yield mean value considered is 2300 kg/ha. The use of 3 kg/ha of fertilizer and 2kg/ha of herbicide are considered. In the area of study, the straw from the collected seeds is usually left in the field as fertilizer, so the straw is considered a co-product used as fertilizer for next year.