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

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