1. Concepts of Soil

Soils are natural unconsolidated materials on the surface of the earth and are composed of solid, liquid, and gas. They have organic as well as inorganic matter, which are intimately mixed together by natural processes. By this mixing and transforming, they are aggregated into a porous body. The pores accommodate air and water. Thus, there are four major components of soil—mineral matter, organic matter, water, and air. The soil has evolved through pedogenic processes as a dynamic and a three-dimensional body. Soils have attained the capacity of supporting various ecosystems on the earth. They provide plants with anchorage, nutrients, water, air, and warmth and protect them from toxins. Soils have crucial ecological functions: It is a transformer of energy, it is a recycler of materials, it is a purifier of water, and above all, it functions as an ecosystem component.