Ch 5: Soil Systems and Societies

Ch 5 - Soil Systems and Society

5.1 - Introduction to soil systems

  • Inputs: minerals, organic matter, gases, water
  • Stores: minerals, organic matter, organisms, air, water, nutrients
  • Outputs: losses of minerals, water > the soil profile

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  • Processes:

     1. Transfers: of materials within the soil including biological mixing, leaching, contribute to the organisations of the soil. (horizons) (leaching and evaporation)   2. Transformation: The complete change of materials in the soil(decomposition, weathering, nutrient cycling)

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  • Soil Horizons: (O,A,B,C) and sometimes E:   * O: organic, leaf litter, comes from organisms that die and end up on top of the soil. Fungi, bacteria, and animals will decompose dead materials   * A: mineral layer, topsoil, upper layer, where humus builds up. Humus is formed when partially decomposed organic matter is mixed with fine material particles, when decomposition is incomplete, a layer dark organic matter is formed → humus layer   * E: leached horizon   * B: subsoil, where soluble minerals and organic matter are deposited from the layer above. For example: clay, iron salts are deposited   * C: parent material, bedrock or another medium

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  • Soil structure and texture:   * Ideal soil: loam which is the balance between clay and soil. Is known for its porosity and permeability, water holding ability, aeration, proportion of materials (sand, silt, clay)   * Pore spaces determine water drainage   * Surface area determines water and nutrients retained   * Light, medium, heavy   * Soil texture triangle: illustrates the differences in composition of soils

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  • Horizons:

     1. Top layers → rich in organic material   2. Bottom layers → consist of inorganic material (derived of weathering of rocks, within this, translocation takes place)

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  • Translocation: process in which materials stored and layers are formed by water carrying particles either up or down   * Also occurs in irrigation and in warmer climates where precipitation < evaporation

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  • Leaching: occur when water flows down in the soil, dissolving minerals and transporting them downwards   * Happens in cooler climates when precipitation > evaporation

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  • Loam soils are ideal for agriculture, as they are a mixture of sand, clay, and silt   * Sand particles: ensure good drainage and a good air supply to the roots   * Silt particles: help hold sand and clay particles and can be worked easily   * Clay: retains water and supplies nutrients (fertile)

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  • Porosity: amount of spaces between particles
  • Permeability: the ease at which gases and liquids pass through the soil
  • Acidification of soil: acid rain causing pollution, adversely affecting soil and causing damage to evergreen forestry   * Fertile soil = non-renewable resource   * Nitrates for leaf and stem   * Phosphates: root system   * Potassium: flower head/fruit

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5.2 - Terrestrial food production and food choices

  • LEDC’s: less economically developed countries   * Country with low to moderate industrialisation and low to moderate average GNP per capita
  • MEDC: more economically developed countries   * Highly industrialised country with high average GNP per capita
  • Agribusiness: business of agriculture production   * Includes farking, seed supply, breeding, machinery, and food harvesting
  • Commercial agriculture: large scale production of crops and livestock for sale
  • Subsistence agriculture (or farming): farming or self sufficing to grow enough for a family

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  • Our food choices are determined by:   * Climate, ecological conditions: adapt through irrigation/greenhouses   * Cultural and religious reasons   * Political reasons: determined by governments to manipulate production   * Socio-economic reasons: market forces determine supply and demand in a free market economy
  • Livestock: useful means of converting plant material
  • Harvesting: requires the removal of biomass from the field, net loss of biomass, nutrients, minerals. Crop rotation addresses loss of soil fertility

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  • Factors which cause a decrease in agricultural land: soil erosion, salinisation, desertification, urbination
  • How to increase sustainability of food supplies:   * Maximising yield: improving tech   * Reduce food storage: improve storage → LEDC: waste of production and storage. MEDC → consumption (applying stricter standards in supermarkets)   * Monitoring and control: regulate imports and exports to reduce unsustainable agricultural practices   * Diet and food: reduce meat, different crops, more protein   * Reduce food processing: decrease use of transport and packaging → overall decrease in energy use

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5.3 - Soil degradation and conservation

  • Processes:

     1. Erosion is a process which takes away the soil. Occurs when there is no vegetation in the soil   2. Making soil less sustainable for use:      * Chemicals entering soil → renders soil useless (long term)      * Human activities, overgrazing, deforestation, unsustainable agriculture

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  • Overgrazing: too many animals graze in the same area, leaves bare patches (roots done hold soil together
  • Overcropping: depletes soil nutrients and makes soil dry (risk of erosion), reduced soil fertility
  • Deforestation: removal of forests, removal of vegetation leads to erosion
  • Unsustainable agricultural techniques: cannot be applied long term, removal of crops after harvest (erosion), ploughing in direction of the slope, excessive use of pesticide, irrigation → can cause salinisation as minerals
  • Monocropping: nutrients are depleted and soil loses fertility
  • Urbanisation: increasing number of people that live in urban areas, potential land for agricultural land for agriculture has cities built on it

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  • Soil erosion

     1. Soil conditions: chalk, crushed limestone, counters soil acidification, lime   2. Wind reduction: plant trees/bushes between fields   3. Soil conserving cultivation techniques: terracing, ploughing, counter farming   4. Improve irrigation techniques

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