Wikipedia
Fertilizer
Fertilizers are soil amendments applied to promote plant and fruit growth. Fertilizers are usually applied either on soil or onto leaves (foliar feeding).
Fertilizers can also be applied to aquatic environments for geoengineering, notably Ocean fertilization.
Chemical content
Fertilizers typically provide, in varying proportions, the three major plant nutrients: nitrogen, phosphorus, and potassium, known shorthand as N-P-K). They may also provide secondary plant nutrients such as calcium, sulfur, magnesium. Micronutrients may be provided: boron, chlorine, manganese, iron, zinc, copper, molybdenum and selenium.
Macronutrients and micronutrients
Fertilizers can be classified by their macronutrients and micronutrients content (concentrations by dry matter). There are six macronutrients: nitrogen, phosphorus, and potassium, often termed "primary macronutrients" because their availability is usually managed with NPK fertilizers, and the "secondary macronutrients" — calcium, magnesium, and sulfur — which are required in roughly similar quantities but whose availability is often managed as part of liming and manuring practices rather than fertilizers.
The macronutrients are consumed in larger quantities and normally present as a whole number or tenths of percentages in plant tissues (on a dry matter weight basis). There are many micronutrients, required in concentrations ranging from 5 to 100 parts per million (ppm) by mass. Plant micronutrients include iron (Fe), manganese (Mn), boron (B), copper (Cu), molybdenum (Mo), nickel (Ni), chlorine (Cl), and zinc (Zn).
Macronutrient fertilizers
Synthesized materials are also called artificial, and may be described as straight, where the product predominantly contains the three primary ingredients of nitrogen (N), phosphorus (P), and potassium (K), (known as N-P-K fertilizers or compound fertilizers when elements are mixed intentionally).
Reporting of N-P-K
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