Why do farmers use a combination of manures and fertilizers in their field?

Manures are plant and animals residues only. They are organic and contain very less concentration of plant nutrients. Manures are absorbed slowly by the plants. They make the soil fertile. Whereas fertilizers are inorganic salts but contain a very high concentration of essential plant nutrients. Fertilizers are highly absorbable. So manures are mixed with fertilizers to provide all the essential nutrients to the plants. A combination of manures and fertilizers promote healthy growth and higher yield of crops. It also helps to improve the texture and quality of the soil.