Effects of different applying amounts of N fertilizer on the accumulated content of nitrate in the Chinese cabbage

The effects of different applying amounts of N fertilizer on the yield of Chinese cabbage and the content of accumulated nitrate in the cabbage and soil are studied in this paper．The results show that the cabbage yield and the net yield rate are increased with the increase of the application of N fertilizer．The rational applying amount of N fertilizer to the cabbage is 427．5kg／hm²．The content of nitrate is higher in outside leaves than in inner ones and it is increased with the increase of N fertilizer application．The outside leaves contain a certain amount of nitrate in low N application，but the nitrate content increases with the growth of the cabbage when the N fertilizer application is high．The nitrate kept in soils is increa sed when N fertilizer is applied．Applying higher amount of N fertilizer in a traditional cultivating practice，the low yield and net yield will be got，the ripe Season is delayed，and a quite amount of nitrate is accumulated in soil profile．Therefore，the fertilizer use efficiency is low．