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化肥施入农田就可使庄稼增产,这是因为化肥含有庄稼要“吃”的营养物质。问题是需要什么养料,什么时候吸收最好才能让化肥物尽其用,庄稼吃饱长好,取得最高的经济效益。这里先从作物营养说起。 一、作物生长发育必需的营养元素 一棵生长着的庄稼,含水分75～95％,干物质5～25％。经过一二百年研究,至今知道一般作物生长发育必需的营养元素有碳、氢、氧、氮、磷、钾、钙、镁、硫、铁、锰、铜、锌、硼、钼、氯等16种。此外,钠、硅等元素虽未肯定为作物所必需,但对某些作物生长却是有益的。据报道,稀土元素可使橡胶增产15％以上,钒和钴元素对豆科作物也有妙用,引起了人们不断探索和试验。 若按含量来分,碳、氢、氧、氮、磷、钾、钙、镁、硫等9种称为大量元素,其余7种则叫微量元素。在大最元素中,作物对氮、磷、钾的需要量较多,而土壤往往又难以供足,只有通过施肥才能满足需要。因此,将氮、磷、钾称为“三要素”,含有这几种元素物质的化肥也就叫“三要
Fertilizers can be applied to farmland to increase production because fertilizers contain nutrients that crops need to “eat.” The question is what kind of nourishment is needed and when is the best way to make the best use of chemical fertilizers? The crops are well fed and the highest economic benefits are achieved. Speaking of crop nutrition here. First, crop growth and development of essential nutrients A growing crop, containing moisture 75 to 95%, dry matter 5 to 25%. After one or two hundred years of research, so far know that the nutrients necessary for the growth and development of crops are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum, chlorine, etc. 16 species. In addition, elements such as sodium and silicon are not necessarily required for crops, but are beneficial for some crops. It is reported that rare earth elements can increase rubber production by more than 15%, vanadium and cobalt elements of fabaceous crops have magical, causing people to continue to explore and test. If divided by content, carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and other nine kinds of known as a large number of elements, while the remaining seven are called trace elements. Among the most significant elements, the demand for nitrogen, phosphorus and potassium is higher in crops, and the soil is often more difficult to feed. Only through fertilization can crops meet their needs. Therefore, the nitrogen, phosphorus and potassium as the “three elements”, containing these elements of the chemical fertilizer is called "three to