尿素是固体氮肥中含氮最高的氮肥,属中性肥料,长期施用,不会酸化或碱化土壤,对土壤无破坏作用。无论北方的石灰性土壤还是南方的酸性土壤,无论旱地还是水田,施用尿素均无副作用,即使在盐碱土上施用,也不会增加有害盐分浓度。由于尿素与碳酸氢铵、硫酸铵等铵态氮肥和硝酸铵、硝酸钙、硝酸钾等硝态氮肥不同,尿素中的氮素呈有机状态即酰胺态的形态存在。所以,在作追肥施用上,既有相同处,又有不同之处。总结各地追施尿素经验,应作到如下“四要”和 Urea is the nitrogenous nitrogen fertilizer with the highest nitrogen content in solid nitrogenous fertilizers. It is a neutral fertilizer and can be used for a long time without acidifying or alkalizing the soil and has no damaging effect on the soil. Regardless of the calcareous soil in the north or the acidic soil in the south, the application of urea has no side effect in both dryland and paddy field, and does not increase the harmful salt concentration even when applied on saline-alkali soil. As urea and ammonium bicarbonate, ammonium sulfate and other ammonium nitrogen fertilizer and ammonium nitrate, calcium nitrate, potassium nitrate and other nitrate nitrogen fertilizers, urea nitrogen was organic state that the amide state exists. Therefore, the application of top dressing, both the same place, there are differences. Summarize the experience of topdressing urea all over the world, we should make the following “four requirements”