多年生果树在生长发育的年周期变化中,常常出现营养失调,形成大小年结果,或因缺少某种元素,出现生理病害。针对这些问题,采用一般的施肥和喷药方法短期难于收效。例如,在石灰性土壤中,柑桔出现缺铁失绿,土壤中铁化物的含量虽高,但溶解度低,无法为果树所利用,而土壤中施入有效性铁如硫酸亚铁或尿素铁,又会被迅速固定,失去作用。螫合铁虽然效果好,但施入土壤用量较多,成本太高,难于在大面积应用。叶面喷施铁 Perennial fruit trees in the annual growth and development changes, often appear in malnutrition, the formation of annual results, or due to the lack of a certain element, the emergence of physiological diseases. In response to these problems, using the general method of fertilization and spraying difficult to be effective in the short term. For example, in calcareous soils citrus is characterized by lack of iron and green, and high levels of ferric in soil, but its solubility is low and can not be used by fruit trees. However, effective iron such as ferrous sulphate or urea, Will be quickly fixed, lost its effect. Ferro-iron although the effect is good, but the amount of soil into more, the cost is too high, difficult to apply in a large area. Foliar spraying iron