Their leaves and roots are added to the soil. The plants mature, die and new ones take their place. Soil formation is influenced by organisms (such as plants), micro-organisms (such as bacteria or fungi), burrowing insects, animals and humans.Īs soil forms, plants begin to grow in it. For example, soils formed from granite are often sandy and infertile whereas basalt under moist conditions breaks down to form fertile, clay soils. The types of parent materials and the conditions under which they break down will influence the properties of the soil formed. Water, wind, temperature change, gravity, chemical interaction, living organisms and pressure differences all help break down parent material. They are produced from rocks (parent material) through the processes of weathering and natural erosion. Interactions between these factors produce an infinite variety of soils across the earth’s surface. topography-grade of slope affecting drainage, erosion and deposition.climate-affecting the rate of weathering and organic decomposition.living organisms-influencing soil formation.parent material-minerals forming the basis of soil.Five main interacting factors affect the formation of soil: These processes can be very slow, taking many tens of thousands of years. The accumulation of material through the action of water, wind and gravity also contributes to soil formation. Burrowing animals help water and air get into rock, and plant roots can grow into cracks in the rock, making it split. biological weathering-the breakdown of rocks by living things.This can happen when the minerals within rocks react with water, air or other chemicals. chemical weathering-breakdown of rocks through a change in their chemical makeup.Temperature changes, abrasion (when rocks collide with each other) or frost can all cause rocks to break down. physical weathering-breakdown of rocks from the result of a mechanical action. Weathering can be a physical, chemical or biological process: Soil forms continuously, but slowly, from the gradual breakdown of rocks through weathering. The properties of horizons are used to distinguish between soils and determine land-use potential. Some soils also have an O horizon mainly consisting of plant litter which has accumulated on the soil surface. C horizon-underlying weathered rock (from which the A and B horizons form).Texture may be heavier than the A horizon too. It generally has a lighter colour and less biological activity than the A horizon. This horizon is often less fertile than the topsoil but holds more moisture. The A horizon is usually darker than other horizons because of the organic materials. most plant roots, earthworms, insects and micro-organisms are active). A horizon-humus-rich topsoil where nutrient, organic matter and biological activity are highest (i.e.A soil profile may have soil horizons that are easy or difficult to distinguish. Soil horizons are the layers in the soil as you move down the soil profile. Most soil profiles cover the earth as 2 main layers- topsoil and subsoil. As soils develop over time, layers (or horizons) form a soil profile.
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