Responses of yield and quality to nitrogen fertilization for oilseed rape cultivars with different nitrogen efficiencies

To investigate responses of seed yield and quality of oilseed rape to nitrogen (N) application levels, and inspect relationship between N use efficiency and seed quality, the sand culture was conducted to study on changes of N efficiencies, seed yields and qualities of two oilseed rape cultivars with different N efficiencies under five N application levels, 06, 3, 6, 12 and 15 mmol/L (expressed with N1-N5 respectively). The results show that the seed yields, oil yields and protein contents are increased with the increasing of N application levels, while the N efficiencies and oil contents are decreased. The changes of fatty acids in seeds are small, the contents of erucic acid and arachidonic acid are slightly decreased with the increasing of the N application levels, and the contents of palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid are not obviously changed. Compared with the low N efficiency cultivar, the changes of seed yield, contents of erucic acid and arachidonic acid of the high N efficiency cultivar are bigger with the increasing of the N application levels, while the changes of oil content are smaller. The seed yield, oil content and oil yield of the high N efficiency cultivar are higher than those of the low N efficiency cultivar under the 5 N application levels. The linoleic acid content of the high N efficiency cultivar is higher than that of the low N efficiency cultivar, while the linolenic acid content of the high N efficiency cultivar is lower than that of the low N efficiency cultivar. There are no significant differences of seed protein, palmitic acid, stearic acid and oleic acid contents between the two cultivars. It can be concluded that increasing N application level is advantage for increasing oil yield, especially for the high N efficiency cultivar, but composition of fatty acids is less influenced. Therefore, the oil content and seed quality of the high N efficiency cultivar are not be decreased by high N absorption and use efficiency