尽管施用化学氮肥是提高作物产量的必要措施，但长期大量施用能引起硝态氮在根区以下土层的无效累积。
Although using chemical fertilizer was a necessary measure to increase crop yields, it could cause a large number of nitrate zone of invalid accumulation in the soil.
液氨主要用作制冷剂及用于制取铵盐和氮肥，是化学工业中一种重要的、存在危险性的化学品。
Liquid ammonia, mainly used as refrigerant or to make Ammonium and nitrogen, is an important yet dangerous chemical.
但化学肥料尤其是氮肥施用量过多，极易导致产品质量下降、环境污染等问题。
But the use of much fertilizer results in decreasing of quality and a series of serious entironment problems.
本文所研究的氮肥如未特殊说明，均指化学合成氮肥（CF-N）。
Without special instructions, this paper studied "nitrogen" is to synthetic fertilizer (CF-N).
结果表明：在绿肥全部还田条件下，不同氮肥用量对烤烟株高、烟叶spad值、烟株干物质累积以及烤后烟叶产量、产值和化学成分均有一定的影响。
Results showed that nitrogen fertilization rate significantly affected tobacco plant growth, leaf SPAD value, dry matter accumulation, leaf yield, economic value as well as chemical components.
基于化肥的农业化学要求讨论和评价缓释氮肥：（1）缓释氮肥的农业化学特点及其肥效；
Slow release nitrogen fertilizers are discussed and evaluated in view of agrochemical considerations: (1) the agrochemical features and the efficiency of slow release fertilizer;
基于化肥的农业化学要求讨论和评价缓释氮肥：（1）缓释氮肥的农业化学特点及其肥效；
Slow release nitrogen fertilizers are discussed and evaluated in view of agrochemical considerations: (1) the agrochemical features and the efficiency of slow release fertilizer;
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