植物生长发育必需16种元素，但对其需要量有很大差别，习惯上把碳、氢、氧、氮、磷、钾称为大量元素，钙、镁、硫、氯称为中量元素，把需要量少的，含量在0.01%以下的6种元素称为微量元素。植物对氮、磷、钾需要较多，而土壤又往往不能满足作物的需要，经常要通过施肥来供应作物的需要，故称它们为“肥料三要素”。有些元素虽然不是必需元素，但它们对植物有一定的营养作用，这些元素被称为有益元素，如钛(Ti),它能够激活微量元素的活性，促进植物对营养的吸收，同时对果实的增色有特殊的作用，还有钴(Co)，它是非必需元素，但它是豆科作物根瘤菌固氮时必需的元素，因此它对豆科的生长有良好的影响。钠(Na)、硅(Si)、碘(I)、硒(Se)、锶(Sr)镍(Ni)、钒(V)等也是有益元素。超微量元素是指那些在植物体中含量很少很少的(在十万分之几以下)非必需元素，其中有些是有益元素，如硒、镉、汞等元素。

Plant growth and development is necessary 16 kinds of elements, but to its demand amount has very big difference, the habit on carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium is called macroelement, calcium, magnesium, sulfur, chlorine is called a medium amount of elements, the content is in 0.01% of the following 6 kinds of elements called trace elements.Plants need more nitrogen, phosphorus and potassium, but the soil often can not meet the needs of crops, need through fertilization to supply the needs of crops, so they are called "three elements of fertilizer".Some elements is not required element, but they have a certain nutrition effect on plant, these elements are called beneficial elements, such as titanium (Ti), it can activate the activity of the trace elements, promote the plants to absorb nutrition, also has special effect to the grace of the fruit, and cobalt (Co),It is a nonessential element, but it is a leguminous crops rhizobia nitrogen fixation necessary elements, so it has a good effect on the growth of leguminosae. Sodium (Na), silicon (Si), iodine (I), selenium (Se), strontium (Sr), nickel (Ni), vanadium (V) are also beneficial elements.Ultra-micro elements is non-essential elements in plants with very little content (less than a few parts per 100,000), some of which are beneficial elements, such as selenium, cadmium, mercury and so on.