(a) The factors which relate to structure and composition of soil are called edaphic factors. Soil is a very complex medium. A good fertile soil contains mineral matter(40%), organic matter (10%), water(15%) and air (25%). Mineral matter in the soil occurs in the form of particles. Soil can be studied under physical and chemical properties .Edaphic is relating to the physical and chemical conditions of the soil,especially in relation to the plant and animal life it supports.