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The Study of Soil Is Called Pedology Soil The study of soil is called pedology Loam Gley Soil Sand soil Fertile soil Leaching in Soil Soil composition • Mineral matter (rock particles) • Humus • Air • Water • Living organisms What is Humus? • Forms when plants and animals decay and rot. • Large amount of humus results in the soil being fertile. • The darker the soil the richer the humus contents. Humus Air • There is air spaces between the rock particles within the soil. • Air contains nitrogen and oxygen which are important for plant life. Water • Makes up 25% of soil composition. • Water contains minerals for the plants to grow. Living Organisms • Earthworms • Woodlice • Millipedes • Bacteria • Fungi Rock Particles Soil layers (Horizons) Horizons O Horizon: • Layer of vegetation of plant litter A Horizon (top soil): • Upper layer of soil called top soil • Contains humus and is very fertile What is leaching? • During heavy raiinfall, leaching can occur which results in minerals being washed downwards out of the soil. • This may result in a hard pan forming which is impermeable. Leaching Horizon B Horizon (subsoil) • Light in clour and contains less humus • Contains stones C Horizon (parent rock): • Consists of bedrock and parent material Soil formation factors • Climatic conditions • Parent material • Vegetation • Living organisms • Water • Time Climatic conditions • This is the main influence on soil type. • Rainfall impacts on how much erosion occurs and leaching. • Heat impacts on the vegetation of an area. Parent material • This is the original rock which has been broken down by weathering. • Produces tiny mineral particles to form soil. Vegetation • When vegetation dies it is broken down into humus. • Humus give the soil its fertility. Living Organisms • Soil is broken up by living organisms. • Worms eat organic matter and mix the layers of the soil. • Plant roots help prevent soil erosion by binding it together. Water • Minerals can be washed out of the soil by leaching. • The amount of water depends on the soil texture. (clay soil holds a lot of moisture). Soil texture • Texture is when a soil is fine or coarse. • Soils can be sandy, clay or loam. Sandy soils • Dry, light and are well drained. • Sandy soils can result in the soil losing its nutrients. Clay soils • Heavy texture which prevents water passing through it. • Can be sometimes waterloggedand difficult to plough. • Suitable for pastoral (grassland) farming. Loam soils • Consist of a mixture of sand, silt and clay. • Well drained • Retains minerals well Soil types • Brown earth • Peat • Podzol • Gley • Lactosol Brown Earth • Formed in areas where deciduous forests are found. WHY IS THIS? Brown earth • Dark brown in colour (rich organic humus) • Fertile topsoil • Suitable for growing crops A horizon = Humus, little leaching B horizon = less humus C horizon = parent material Peat Soil • Dark in colour • Mountain and low lying regions • Poor drainage (water logged) Rich in humus, however, it is infertile. WHY? Peat soils A horizon = Dark colour, large amount of water B horizon = Grey colour C horizon = Impermeable bed rock Podzols • Developed in cold and wet areas. • Covered by coniferous forests. • Small amount of plant litter • A lot of leaching due to heavy rain. • Low in humus • Found in poorly drained low land areas in cork. Solutions • Use fertilisers • Crop rotation • Irrigation • Ploughing methods Gley • Grey in colour • Rock beneath is impermeable (shale) • Water logged • Infertile • Pastoral farming. Latosols • Red tropical soils • Dry winter season and wet summer season. • High temperature and humidity which results in organic matter broken down quickly into humus • Leaching is also common in this area. Why are the soils red? Deforestation How does deforestation lead to poor soil quality? Deforestation Deforestation • How does deforestation lead to flooding in many areas? ITALY Southern Italy has been deforested and soil has become infertile. Much of the soil has been washed down the slopes of the Apennines. Solutions • Describe two methods of reducing the impact of deforestation on the soil quality? How has farming affected the soil quality? • Overcropping • Monoculture • Overgrazing Overgrazing Monoculture .
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