Chemical fertilizers are not complex. They can have three main nutrients that plants need added to the soil and three other nutrients that sometimes need to be added. There are also only three forms that chemical fertilizers can come in. Also, gardeners get to decide whether they want to use chemical fertilizers that contain several nutrients or if they want to add different nutrients in individually.
Fertilizers are often classified into one of two types: chemical and organic. The higher concentration of nutrients in chemical fertilizers makes it possible to add too much and damage the plants, according to Oregon State University. However, chemical fertilizers contain fewer unneeded or harmful elements that can be found in organic fertilizers. Chemical fertilizers also enter into the soil more quickly than organic fertilizers because organic fertilizers have to wait for fungi and bacteria to break down the fertilizer.
Chemical fertilizers can be classified based on the kinds of nutrients that are contained in them. Many chemical fertilizers contain nitrogen, potassium and phosphorus, which are the three most commonly needed plant nutrients, according to Michigan State University. The amount of each nutrient required is based on the kind of plant that is being grown and the amount of each nutrient that is present in the soil based on nutrient analysis. Nutrient analysis is conducted by taking a part of the soil and sending it to a lab at a municipality or university for testing.
Chemical fertilizers can also be classified based on whether or not they are in a solid, liquid or gaseous form. Anhydrous ammonia is the gaseous form of chemical fertilizer; it is technically in liquid form but is put under pressure so that it is released like a gas, according to Michigan State University. Liquid fertilizers are sprayed into the soil or added to water that is used to water the plants. Solid fertilizers are often dissolved into a liquid before they are used.
Some chemical fertilizers are pure nutrient fertilizers. Anhydrous ammonia, aqua ammonia, urea, ammonium sulfate, calcium nitrate, potassium nitrate and sodium nitrate are pure nitrogen fertilizers. Rock phosphate, superphosphate, diammonium phosphate and monoammonium phosphate are pure phosphate fertilizers. Potassium chloride, potassium sulfate, potassium hydroxide and potassium nitrate are potassium fertilizers, according to Michigan State University.
Other nutrients are often added to the soil to raise or lower the soil pH and add magnesium, calcium and sulfur. Lime is added to soil to increase its calcium and magnesium and raise soil pH. Iron sulfate, aluminum sulfate or elemental sulfate are used to lower pH and add sulfur to the soil, according to the University of Minnesota.