植物生長需要各种养料。其中二氧化碳可以大量从空气和土壤中取得;水可以从天然雨水或人工灌溉的水取得;鈣、鎂、鉄、硫、矽、鋁、鈉等也普遍存在于土壤里。唯有氮、磷、鉀,一般的土壤中含量比較少,而植物又需要比較多;因此,必須以合有氮、磷、鉀的化合物,作为肥料加入土壤中,以保証植物的营养。肥料如果按照成份分类,可以分为氮肥(如硫酸銨、硝酸銨和其他含氮鹽类)、磷肥(如过磷酸鈣、重过磷酸鈣等)、鉀肥(如氯化鉀、硫酸鉀等)三类。但是如果按照生產方法來区分,却可以分为自給肥料(如人畜糞尿、堆肥、綠肥、草木灰、海藻灰、魚滓等)和化学肥料(就是經过化学方法加工制得的,如硫酸銨、过磷酸鈣、硫酸鉀等)兩类。施用氮肥,可以增加植物的蛋白質含量,促進它的生長,尤其是促進它的莖和叶的生長。磷肥能 Plant growth requires various nutrients. Carbon dioxide can be obtained in large quantities from air and soil; water can be obtained from natural rainwater or artificially irrigated water; calcium, magnesium, strontium, sulfur, barium, aluminum, sodium, etc. are also commonly found in soil. Only nitrogen, phosphorus, and potassium are common in soils, but plants need more. Therefore, compounds containing nitrogen, phosphorus, and potassium must be added as fertilizers to ensure the nutrition of plants. Fertilizers can be classified into nitrogenous fertilizers (such as ammonium sulfate, ammonium nitrate, and other nitrogenous salts), phosphate fertilizers (such as superphosphate, heavy superphosphate, etc.), potash fertilizers (such as potassium chloride, potassium sulfate, etc.) if they are classified according to their composition. Three types. However, if they are differentiated according to the production method, they can be divided into self-sufficient fertilizers (such as manure, compost, green manure, grass ash, seaweed ash, fish gills, etc.) and chemical fertilizers (which are obtained through chemical processing, such as ammonium sulfate, Superphosphate, potassium sulfate, etc.) Two types. The application of nitrogen fertilizer can increase the protein content of the plant, promote its growth, and in particular promote the growth of its stems and leaves. Phosphorus fertilizer