Influence and assessment of nitrogen rates on nitrate content and nutrient quality of Chinese cabbage (B. Chinensis L.)

Field experiments on two soil fertility conditions were carried out to study the influence of nitrogen rates on nitrate content and nutrient quality of Chinese cabbage.The results showed that a significant quadratic regression existed between nitrogen rates and yield of Chinese cabbage on two soil fertility conditions.The yield of Chinese cabbage on medium and low soil fertility was increased by 141.2%～309.4%and 149.5%～617.6%,respectively.On low soil fertility the yield of Chinese cabbage was only 28.6%～49.5% of that on medium soil fertility.The nitrate content was increased by 9.9%～33.3%(on medium soil fertility,except N 75 kg·hm-2 treatment) and 240.3%～363.6%(on low soil fertility) respectively by applying nitrogen(N) 75～300 kg·hm-2.In the same treatment,nitrate content of Chinese cabbage was higher on medium soil fertility than on low soil fertility except(N) 150 kg·hm-2 treatment.On medium soil fertility Vc content in Chinese cabbage was decreased,the content of amino acid was increased and the content of soluble sugar was affected little with applying nitrogen(N) fertilizer.But the content of Vc,soluble sugar and amino acid was decreased on low soil fertility.