Chemical fertilizers are defined as fertilizers consist of inorganic chemicals which could be synthesized artificially. Some people call chemical fertilizers as Straight fertilizers. They are those which supply only one primary plant nutrient, namely nitrogen or phosphorus or potassium. E.g.: Urea, ammonium sulphate, potassium chloride and potassium sulphate. Agriculture practitioners sometimes will mix few types of chemical fertilizers to formulate desired NPK ratio before application. It is relatively cost-saving method to manure crops but it requires knowledge and good understanding of soil nutrient requirement.
Chemical fertilizer refers to the fertilizer made by chemical synthesis or chemical reactions, whose ingredients contain a certain quantity of nutrients for the plants, such as nitrogen, phosphorus, potassium, magnesium, calcium, sulfur, boron, copper, zinc, manganese, iron and molybdenum, and so on, including simple-substances and compound fertilizers.
Chemical fertilizer always differs from the natural substances such as rock phosphate. After acid treatment (such as sulfuric acid), it will become chemical phosphorus fertilizer, such as calcium superphosphate. The chemical fertilizer could be fast- or slow-released fertilizer. From the features of solubility, it can also be classified into soluble and insoluble fertilizers. Those soluble ones can be applied not only to soil, but also to those fertilizers for foliage dressing.
While applying the chemical fertilizer, it is important to fertilize according to the demands of crops at proper time, with proper amount, in proper way, at proper place, and with the proper sort of fertilizers. For instance, it often occurs that the soil becomes acidic because ammonium sulfate and single supersphosphate have been used for a long period. Apart from that, if the paddy rice is applied too much nitrogen, the leaves will become dark green, and serious rice blast might occur. Overdose or improper application of chemical fertilizers would not affect the production and quality of crops directly, but also have an indirect impact on people health. If the vegetable absorb too much nitrate, it is as harmful to people as bacons that contain nitrate, so it should be carefully concerned. When it comes to the quality of exquisite farming crops, soil plays a very important role; thus, the research on the relationship between crop quality and soil nutrients cannot be ignored.
It is important to apply fertilizers in a balanced way. There are a proportion of cations nutrient elements that crops absorb from the soil (such as K+, Na+, Mg++, Ca++, and some other microelements). For example, potassium fertilizer could increase the content of potassium in the leaves and reduce the amount of other cations. If applying too much potassium fertilizer, it could lead to a deficiency of Mg or Ca for the crops. This is called the ion antagonism. This henomenon can usually been seen in the fruit trees. As a result, the concept of balance between element absorption’s synergism and antagonism should be kept in mind.
The amount of chemical fertilizer applied should be concerned. Some short-term crops are cultivated very intensively, so fertilizers might be over-applied, which would cause the problem of salt deposit.