北方褐土区土壤硝态氮运移动态及合理施肥调控

Moving dynamics of soil nitrate and its fertilization controlling in summer maize field

通过设计不同纯氮（N）施入水平（分别为0、150、300、600、900和1200 kg/hm^2共6个处理）,重点研究了北方褐土区夏玉米大田土壤硝态氮（NO3^--N）运移动态,并讨论了夏玉米N肥的经济环保施用量及其相关机制。试验结果表明,土壤-作物系统内土壤NO3^--N垂直方向上的运移有向上、向下两个方向。不同生育时期土壤NO3^--N运移特征不同,拔节期以前,0-40 cm土层随N肥用量的增加,土壤NO3^--N含量快速增加,40 cm以下深度土壤NO3^--N含量变化不明显,随植株的生长和根系的壮大,0-100 cm土层内的NO3^--N整体运移活跃。土壤有自动调节NO3^--N含量的功能,各土层NO3^--N含量均存在一个最低点,其中耕层为3.1 mg/kg附近;玉米旺盛生长期各土层内土壤NO3^--N饱和值在20.33 mg/kg附近,施肥量过多,NO3^--N向下运移,造成资源浪费和对土壤环境质量的威胁。北方褐土区夏玉米最高纯N施用量应控制在600 kg/hm^2以内,300 kg/hm^2（纯N）是最为环保、经济的施肥量。

In order to study economical and environmental nitrogen （N） fertlization in summer maize in North China Plain, field experiment was conducted at Wang Wenhua＇s field in Luojiazhuang village, Zhengding county. According designing 6 N rates （0, 150, 300, 600, 900, 1200 kg/hm^2）, this paper studied the moving dynamic status of soil nitrate nitrogen （NO3^ -- N） in summer maize field, and discusses the economical and environmental N rates and its theories. The main results as follows： for soil NO3^ - - N there were two orientation of up and down in uprightness moving in soil - crop system. There were different moving characters for soil NO3^ -- N in different growth stages： up to 40 cm depth before stem elongation stage soil NO3^- - N content increased speed with N rates increasing, while there was no clearly changes under 40 cm depth. With the growth of plant and the development of root, the movement of 0 - 100 cm depth soil NO3^-- N became activated. It indicated the absorbing and applying of plant to N fertilization mainly concentrated in root depth soil layer. The result showed the lowest point of balance for soil NO3^ -- N content in one layer was about 3.1 mg/kg and in the bloom of maize growth the saturated point in one soil was about 20.33 mg/kg. The highest N rate for environmental was under 600 kg/hm^2, and the economical rate was 300 kg/hm^2.