Urea

Among all the known elements in nature, Nitrogen (N), Phosphorus (P) and Potassium (K) has more effects on growth of plants rather than the others, so some combinations of these are used as a fertilizer for agriculture. Urea, a white crystalline organic chemical compound with the highest Nitrogen content (about 46 percent) is the most famous and important nitrogen fertilizer which can be used for most of plants and so has these advantages: not changing in the concentration of salts in soil and not leaving behind salts in the soil, neutral in pH and can adapt to almost all kinds of soils, providing a high nitrogen content, which is essential in plant metabolism in direct relation to the number of stems and leaves, which absorb light for photosynthesis. In addition, nitrogen is present in vitamins and proteins and is related to the protein content of cereals. Naturally it is a waste product by metabolizing protein in humans as well as other mammals, amphibians and some fish.
The 70% of produced urea in the world is used in agriculture and the rest is used in production of melamine powder as animal food and medical applications. Urea is also used in AdBlue (Urea without UF), a liquid solution which its main purpose is to help reduce pollutive emissions that occur when using vehicles with diesel engines.