Fertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil (for uptake by plant roots) or, by foliar feeding (for uptake through leaves).

Fertilizers can be placed into the categories of organic fertilizers (composed of plant or animal matter), or inorganic fertilizers (made of simple, non-carbonaceous chemicals or minerals).

'Organic' fertilizers are composed of 'naturally' occurring compounds such as peat manufactured through natural processes (such as composting) or naturally occurring mineral deposits; or in the case of 'inorganic' fertilizers, manufactured through chemical processes (such as the Haber process) or from naturally occurring deposits that have been chemically altered (e.g. concentrated triple superphosphate).

Properly applied,

on soil productivity of the soilFact: date=April 2009.

Content of fertilizer

Fertilizers typically provide, in varying proportions, the three major plant nutrients: nitrogen, phosphorus, potassium known shorthand as N-P-K); the secondary plant nutrients (calcium, sulfur, magnesium) and sometimes trace elements (or micronutrients) with a role in plant or animal nutrition: boron, chlorine, manganese, iron, zinc, copper, molybdenum and (in some countries) selenium.

Organic vs. Non-organic

Both organic and inorganic fertilizers were called "manure" derived from the French expression for manual (of or belonging to the hand) tillage, however, this term is currently restricted to organic manure. Though nitrogen is plentiful in the Earth's atmosphere, relatively few plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a plant-accessible form).

It is believed by some that 'organic' agricultural methods are more environmentally friendly and better maintain soil organic matter (SOM) levels. There are some scientific studies that support this position.

Regardless of the source, fertilization results in increased unharvested plant biomass left on the soil surface and crop residues remaining in the soilFact: date=March 2009.

History

While manure, cinder and ironmaking slag have been used to improve crops for centuries, the use of fertilizers is arguably

Key figures in Europe

In the 1730s, Viscount Charles Townshend (1674–1738) first studied the improving effects of the four crop rotation system that he had observed in use in Flanders. For this he gained the nickname

Justus von Liebig

Chemist Justus von Liebig (1803–1883) contributed greatly to the advancement in the understanding of plant nutrition. His influential works first denounced the vitalist theory of humus, arguing first the importance of ammonia, and later promoting the importance of inorganic minerals to plant nutrition. Primarily Liebig's work succeeded in exposition of questions for agricultural science to address over the next 50 yearsFact: date=April 2009.