Compound used in fertilizers are two substances, Urea (4 letters) and Niter (5 letters). Urea is a colorless, odorless solid organic compound made up of carbon, nitrogen, oxygen, and hydrogen. It is the most common nitrogen-containing compound found in nature and is an important source of nitrogen for plants. Niter is a naturally occurring mineral composed of potassium nitrate, which is a key component of many fertilizers. It is also used in the manufacture of gunpowder and other explosives. Both Urea and Niter are essential components of fertilizers, as they provide essential nutrients to plants and help promote healthy growth.