ABSTRACT
The fertilizer industry developed in stages with phosphate materials in the 1840s, potassium materials in the 1870s, and the nitrogen materials about 1900. Ammonia synthesis occurs when the N2 and H2 gases are passed over an Iron catalyst, promoted with potassium and alumina, at high temperature and pressure. Ammonium polyphosphates have formed an important part of the liquid fertilizer industry. Urea is more expensive than NH3, because there are additional manufacturing steps and greater transportation costs. It requires no specialized equipment for storage and handling and is preferred over NH3 in situations where the fertilizer is applied by broadcast on lawns or field crops. A cover crop that grows in the fall and early spring takes up mineral soil and converts it into organic matter, thereby reducing leaching and denitrification losses. Nitrification is an important soil-acidifying process; when ammonium fertilizers are used, there is considerable potential to increase soil acidity.
