Without research and the use of fertilizers, today's human population could not survive. Limited amounts of nutrients in the soil will be consumed by plants in just a few years. We need to feed the soil with nutrients to be able to use it again as farm land. 

Nutrients for soil are called fertilizers. These are what plants need to grow, but what are the materials that plants need. How many types of fertilizers exist? Where do they come from or how are they made? Is any fertilizer good for any plant?