OBJECTIVE FORESTRY

Detailed explanation-1: -The layers of the soil are called horizons . The uppermost horizon is called the topsoil layer. The topsoil layer is a mixture of sand, silt, clay and broken down organic matter, called humus. Humus is rich, highly decomposed organic matter mostly made from dead plants, crunched-up leaves, dead insects and twigs.

Detailed explanation-2: -Called the A horizon, the topsoil is usually the darkest layer of the soil because it has the highest proportion of organic material. The topsoil is the region of most intense biological activity: insects, worms, and other animals burrow through it and plants stretch their roots down into it.