Fertilizer

A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macronutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment, or hand-tool methods.

Historically, fertilization came from natural or organic sources: compost, animal manure, human manure, harvested minerals, crop rotations, and byproducts of human-nature industries (e.g. fish processing waste, or bloodmeal from animal slaughter). However, starting in the 19th century, after innovations in plant nutrition following Justus von Liebig's discoveries, an agricultural industry developed around synthetically created agrochemical fertilizers. This transition was important in transforming the global food system towards larger-scale industrial agriculture with large crop yields in monocultures.

The invention of Haber process for producing ammonia for nitrogen in the 20th century combined with amplified chemical production capacity created during World War II led to a boom in using nitrogen fertilizers.