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

• 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)

• 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

• 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

• 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)

• 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

• Leaching: occur when water flows down in the soil, dissolving minerals and transporting them downwards

  • Happens in cooler climates when precipitation > evaporation

• 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)

• 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

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

• 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

• 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

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

• 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

• 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