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据法国试验:在冬油菜所需的全部氮肥中,秋季约占20～25%,春季返青后需50～70%,从开花至成熟需10～20%。到收获时,70%的氮素转移到籽实中(每亩约9.4～16.7斤)。试验表明:每亩施氮从13.4斤至26.7斤时,菜籽产量是随施肥量增加而增加的,但其中从每亩20斤增到26.7斤时,菜籽的含油量要下降。因此,最近施氮量为每亩20斤,如果每亩施氮量大于23.4斤,就要分多次施用。
According to the French test, about 20-25% of all nitrogen fertilizers are needed in winter rape, 50-70% in spring and about 10-20% in flowering and maturity. At harvest, 70% of the nitrogen is transferred to the seed (about 9.4 to 16.7 kg per acre). The results showed that the yield of rapeseed increased with the increase of fertilizer application rate from 13.4 kg to 26.7 kg nitrogen per acre, but the oil content of rapeseed decreased from 20 kg to 26.7 kg per acre. Therefore, the recent nitrogen application rate of 20 kg per mu, if the amount of nitrogen per acre is more than 23.4 kg, it is necessary to sub-multiple applications.