在北京顺义区农科所基地开展田间试验，设置5个氮水平处理，研究不同氮肥用量对甘薯干物质积累及氮磷钾吸收效率的影响。结果表明：施氮量为210 kg/hm2时，甘薯的鲜薯产量达到最大值30.4 t/hm2；甘薯干物质积累量为21423 kg/hm2，氮磷钾累积值也达到最大；当施氮量超过210 kg/hm2时，干物质积累量随着施氮量的增加而不再增加，而呈平台反应；施氮量为210 kg/hm2时，甘薯磷、钾累积值也最大，分别是145.7 kg/hm2和247.4 kg/hm2。因此，本试验条件下甘薯的最佳氮肥用量为210 kg/hm2。

Field experiments were conducted at the station of Shunyi Agriculture Sciences Institute in Beijing. This study is about the effects of 5 levels of nitrogen applying on dry matter accumulation and N, P and K absorption efficiencies of sweet potato. It is indicated that yield reached the highest value of 30.4 t/hm2 at N level of 210 kg/ hm2, and the corresponding dry matter reached 21423 kg/hm2 and the P and K accumulations reached the highest values of 145.7 kg/hm2 and 247.4 kg/hm2. When the N level exceeded 210 kg/hm2, dry matter did not increase with the increase of N applying which showed a platform relationship. We can conclude that 210 kg/hm2 N was the optimum N level for sweet potato.