Soil fertilization is one of the most important tasks in agriculture. Every good farmer is concerned about how to keep or restore soil fertility in order to maintain good yields.

As we saw in Chapter 2, a good soil is not only rich in the basic nutrients including nitrogen, potassium and phosphorous, it is also physically well structured and biologically very active. When the chemical, physical and biological qualities of the soil are well-balanced, we consider it to be optimal soil.

Many farmers are concerned about adding fertility or nutrients, but there are very few who are concerned about and put emphasis on, protecting soil through soil conservation. Nutrients involve the chemical quality of the soil, the latter its physical and biological quality. This is the main reason why erosion is a problem in agricultural land. If we think about it, we will realize that fertilization and conservation are equally important.