OBJECTIVE FORESTRY

Detailed explanation-1: -The horizons are: O (humus or organic): Mostly organic matter such as decomposing leaves. The O horizon is thin in some soils, thick in others, and not present at all in others. A (topsoil): Mostly minerals from parent material with organic matter incorporated.

Detailed explanation-2: -The O horizon is typically at the top of the soil structure and is made up of mostly organic matter. This organic matter is vital to the growth of crops and other plants because it holds nutrients such as carbon, phosphorus, nitrogen and sulfur.

Detailed explanation-3: -The O horizon is an organic layer made of wholly or partially decayed plant and animal debris. The O horizon generally occurs in undisturbed soil, since plowing mixes the organic material into the soil. In a forest, fallen leaves, branches, and other debris make up the O horizon.