一、缺素症的原因氮、磷、钾、钙、镁是作物生长发育所需的大量营养元素。此外,有一些元素虽然需要量少,但缺之不可,称之为微量元素。微量元素中,有铁、锰、锌、铜、钼等金属元素,以及非金属元素硼。铁在土壤中的含量仅次于硅和铝,占第三位,但作物的需要量少,故亦为微量元素。钼、硼也是含量少的。作物吸收微量元素是通过矿物和腐殖质的分解。微量元素不足会产生缺素症,但过量也会引起生理障碍。如缺硼时易产生缺硼症,但因之而每亩施用1—2公斤硼酸,却又会引起硼过剩症。可见微量元素的缺乏与过量之间的数 First, the reasons for the lack of disease Nitrogen, phosphorus, potassium, calcium and magnesium are a large number of nutrients required for crop growth and development. In addition, although there are some elements required less, but missing, called trace elements. Trace elements, iron, manganese, zinc, copper, molybdenum and other metal elements, and non-metallic element boron. Iron content in soil second only to silicon and aluminum, accounting for third place, but the crop needs less, it is also trace elements. Molybdenum, boron is also less content. Crops absorb trace elements through the decomposition of minerals and humus. Insufficient micronutrient deficiency can lead to deficiency, but excess can cause physical disorders. Such as lack of boron prone to boron deficiency, but because of this and the application of 1 kilogram of boric acid per acre, but will cause boron excess disease. Can be seen between the lack of trace elements and the number of excess