追施氮肥水平对菜用甘薯产量、 品质及硝酸盐积累的影响

为探讨菜用甘薯采收后追施氮肥量, 以 ‘徐菜薯 1 号’ 为试材, 在采收后施用不同水平的氮肥, 研究不同氮肥施用量对产量、 品质的影响, 并探讨了施用氮肥后硝酸盐含量随时间的动态变化规律。 结果显示, 随着氮肥施用量的增加, 菜用甘薯蛋白质、 硝酸盐含量显著升高, 黄酮、 维生素 C、 总糖、 多酚含量先升高后下降, 还原糖含量则不断下降。 总体来看, 选择施用 225.0 kg/hm2 氮肥, 菜用甘薯产量最高, 但营养品质差, 施用 75.0、 150.0 kg/hm2 氮肥, 菜用甘薯产量较高、 品质最优; 施用氮肥后菜用甘薯内硝酸盐含量不断增加, 在7 d 左右达到最大值, 而后不断降低, 在 11 d 左右降低到未施用氮肥水平; 菜用甘薯叶色值与氮肥施用量, 蛋白质、 硝酸盐含量等显著相关, 间接反映出菜用甘薯氮素水平。 研究结果表明： 适宜的氮肥施用量可以提高菜用甘薯产量、 营养品质, 降低硝酸含量。 氮肥施用后应留足够的间隔期才能采摘, 以免硝酸盐过量。 测定叶色值可以为合理施肥提供参考。

Effects of Additional Nitrogen Fertilizer Application Level on Yield,Quality and Nitrate Accumulation of

The effects of different nitrogen fertilizer application amount after harvest on the yield, quality and nitrate content changes of vegetable sweet potato were studied based on the cultivar  ‘Xu cai shu 1’. The results showed    that with the increase of nitrogen fertilizer application, the protein and nitrate content of vegetable sweet  potato increased significantly, and the content of flavonoids, vitamin C, total sugar, polyphenol increased first and then decreased, while the reducing sugar content decreased continuously. The highest yield could be achieved after an application of 225.0 kg/hm2 nitrogen fertilizer. Better quality could be achieved for 75.0 kg/hm2 and 150.0 kg/hm2 nitragen application. Nitrate content would increase after nitrogen fertilizer application, reaching  the  highest  at  7th  day and then reduced to the CK in about 11 days. The SPAD value was significantly correlated with the amount             of nitrogen fertilizer application, protein and nitrate content, which indirectly reflected the  nitrogen  level.  It  meant  that suitable application of nitrogen fertilizer would promote both the productivity and quality, and the leaves should    be harvested enough interval after application of nitrogen fertilizer. Leaf color value could provide references for  rational fertilization.