氮肥施用对露地秋季大白菜产量和硝酸盐积累及氮素利用的影响

Effect of Nitrogen Levels on Yield,Nitrate and Nitrogen Utilization of Chinese Cabbage

采用田间小区试验方法,研究了不同氮肥施用量对露地秋季大白菜产量和硝酸盐积累及氮肥利用的影响。结果表明,大白菜产量随氮肥施用量的增加呈增加趋势,施氮平均增产5.5%,平均增收570.4元/hm2,施N量在150kg/hm2左右时大白菜经济效益较高;大白菜球叶总干物质积累与总氮素积累随施氮量的增加均呈先增加后降低的趋势,当施氮量在150和225 kg/hm2时,大白菜球叶总干物质积累与总氮素积累最多;在施N 225 kg/hm2以下时,氮肥利用率和农学效率均较高（分别为31.5%-43.1%和18.5-26.3 kg/kg）,氮肥表观损失较低（31.5-168.4 kg/hm2）,而高量施氮时,氮肥利用率和农学效率显著降低,氮肥表观损失显著增加,表层土壤氮素显著积累,土壤中氮素向深层淋洗的风险显著增加。在本试验条件下,基于产量、经济效益和环境效益的露地秋季大白菜适宜氮素（N）用量为150 kg/hm2左右。

This study was conducted to determine the effect of nitrogen application rates on yield,nitrate and nitrogen utilization of Chinese cabbage under relatively high soil nitrogen fertility level by the field experiment in He village,Zhonghan town,Gaoyi county in Hebei province.The results showed that Chinese cabbage yield tended to increase with increasing nitrogen application.Nitrogen application averagely increased yield of Chinese cabbage by 5.5%,and increased income by 570.4 Yuan/ha,with relatively high yield and income at N rate of about 150 kg/ha applied.Total biomass accumulation and total N uptake of Chinese cabbage tended to increase at first and then decrease,with the highest values of them at N rates of 150 and 225 kg/ha applied.Relatively high recovery rate（31.5%-43.1%）and agronomic efficiency（18.5-26.3 kg/kg）,and relatively low apparent N loss（31.5-168.4 kg/ha） of applied N below 225 kg/ha was found.Whereas recovery rate and agronomic efficiency of applied N at rates of 300-525 kg/ha decreased significantly,and apparent N loss increased greatly,with significant increase of N losses by leaching resulting from distinct increase in nitrogen content in upper soil layer.The proper rate of N of Chinese cabbage based on yield,income and environment was about 150 kg/ha under this experimental condition.