氮、磷、钾、硼、锌、锰是玉米的必须元素。如果土壤中缺乏这些元素,玉米在生长过程中就会出现一系列的病症。缺氮植株较细弱,叶色黄绿,首先是下部老叶从叶尖开始变黄,然后沿中脉伸展呈楔(V)形,叶边缘仍为绿色,最后叶片变黄干枯。缺氮还会引起雌穗形成延迟或雌穗不能发育或穗小粒少产量下降,有的还会造成空秆。防治方法,可基施或追施氮肥,作基肥时每亩用尿素30斤或碳酸氢铵70～80斤,作追肥时每亩 Nitrogen, phosphorus, potassium, boron, zinc and manganese are essential elements of corn. If these elements are absent from the soil, corn will develop a series of conditions during its growth. The nitrogen-deficient plants are faint and the leaves are yellow-green. First, the lower part of the old leaves turn yellow from the tip of the leaves, and then extend along the midrib to form a wedge (V) shape. The edge of the leaves is still green, and finally the leaves turn yellow and dry. Nitrogen deficiency can also lead to the formation of ear delay or ear can not develop or spikelets decreased production, and some will cause empty stalk. Prevention and control methods can be based facilities or topdressing nitrogen fertilizer, when used as basal fertilizer 30 kg of urea per acre or ammonium bicarbonate 70 to 80 kg, top dressing for each mu