一般认为,柑桔叶尖黄化主要是缺少微量元素所致,但据近年国内外有关资料表明,叶面喷施尿素不当是引起柑桔叶尖黄化的又一重要原因。大家知道,供柑桔果树生长所需的氮肥主要来自根部从土壤中的吸收,在果树大量需肥期,氮素的第二来源是通过叶面喷施尿素来获得。在大面积果园生产上,很多果农也非常注重叶面追肥,几乎每次打农药都要加入尿素,并认为这是一举两得的好办法,即是在高温高湿的气候也是如此。然而喷施后常常就出现柑桔叶尖发黄。这是因为尿素中含有的有毒物质缩二脲在高温、高湿和强光照下对柑桔叶片的伤害出现的症状。据国内 Generally believed that citrus leaf tip yellowing is mainly due to the lack of trace elements, but according to domestic and foreign relevant information in recent years show that foliar spray inappropriate urea is caused by citrus leaf tip yellowing another important reason. As we all know, the nitrogen fertilizer needed for the growth of citrus fruit trees mainly comes from the absorption of the roots from the soil. In the period when the fruit trees need fertilizer, the second source of nitrogen is obtained by spraying urea on the foliage. In large-scale orchard production, many fruit growers also pay great attention to foliar fertilizer, and almost every time pesticides are added to urea, and think this is a good way to kill two birds with one stone, that is, in the high temperature and humidity climate is also true. However, citrus leaf tips often appear yellow after spraying. This is because of the symptoms of injury to citrus leaves under the conditions of high temperature, high humidity and strong light, which are the biurets of urea contained in urea. According to China