Winter rapeseed oil content variability at an agricultural cooperative supplying area scale

摘要

The crushing sector pays the agricultural cooperatives for winter rapeseeds in relation with their oil content. The aim of this study was to understand the main variation factors in oil content at the scale of a grain supplying area, in order to elaborate strategies to increase the mean oilseed content of the storage receipt. Experimental data are available from a network of about 70 fields of rapeseed set each year in 2003 and 2004 in the centre of France. The fields were spread over the whole supplying area.The main soil types and crop management of this area were represented. The study focused on 4 varieties, among the most cultivated. The main characteristics of the soil and of the crop management were collected for each field. The yield, thousand seed weight, oil content and protein content of the harvested seeds were measured. The results showed that the seed oil content variability was high: from 43 to 52 % of the dry matter. The main factors influencing the oil content were the soil type (particularly the soil depth and the water capacity), the variety (but the varieties with high oil content levels were not always the most productive), and the N balance (the higher the excess of N fertilization, the lower the oil content). The strategy of the agricultural cooperatives in order to increase the mean oilseed content of their storage receipt is often to advise farmers to grow varieties with high oil content. This study showed that a better adjustment of the N fertilization is also an interesting strategy.Indeed, even if important progress has been made over the past few years, many fields are still overfertilized.