ess unit 5 - soil systems and society

purpose of soil

• space/structure for roots

• provides nutrients (nitrates and phosphates)

• absorbs and releases water

• habitat for detritivores (eat dead organisms e.g. beetles, earthworms) and decomposers (e.g. mold, fungus)

processes that are happening in soil (soil as a bridge)

• composting (converting dead organic matter into soil organic matter)

• air and gas exchange

• water retention

• inorganic molecules

• microbial business

soil organic matter

the fraction of soil that consists of plant or animal tissue in various stages of decomposition

• most important part of a healthy soil

• can be decomposed, releasing nutrients and feeding soil detritivores and decomposers

measurable biotic characteristics of soil

• organic matter

• plant growth

• insects/organisms

measurable abiotic characteristics of soil

• moisture

• pH

• temperature

• salinity

• nutrients

• water retention

• layers (depth of horizons)

• stratification (soil texture)

impact of soil on the biosphere, lithosphere, atmosphere and hydrosphere

atmosphere → soil, through heat energy by radiation

soil → atmosphere, evaporation of water from soil

soil → biosphere, plants absorb nutrients from the soil

biosphere → soil, death decay of organic matter

soil → lithosphere (rocks), production of sedimentary rocks

lithosphere (rocks) → soil, erosion breaks down small rocks into sand particles in soil

soil → hydrosphere, percolation of soil water into groundwater and aquifers

hydrosphere → soil, infiltration of water from rivers

layers of soil (the soil profile)

1. organic matter (layer of plant residues in undecomposed form)

2. surface soil (layer of mineral soil with most organic matter accumulation and soil life)

3. subsoil (accumulates iron, clay, aluminum, and organic compounds - illuviation)

4. parent rock (layer of large unbroken rocks)

5. bedrock (layer of partially weathered bedrock at the base of the soil profile)

soil texture and what does it determine?

the balance between sand, silt and clay

• it determines nutrient availability and drainage

  • sand lets water drain

  • clay holds water which slows infiltration

characteristics of sand soil

• low primary productivity

• always dry

• nutrient poor

• having a lot of dead organic matter would help sand with water retention and to release nutrients during decay

characteristics of clay soil

• quite low primary productivity

• easily compacted, removes air pockets

• easily flooded

• needs to be ploughed often

characteristics of loam soil

• high productivity

• good balance between drainage and drought resistance

• releases nutrients well

typical percentage distribution of different soil types in loam soil

20% clay, 40% sand and 40% silt

different types of nutrients in soil

• macronutrients

• micronutrients

• nitrogen

• iron

• phosphorus

• potassium

• copper

• nickel

• magnesium

• zinc

• sulphur

• molybenum

• cobalt

causes of soil degradation

• soil erosion

  • sheet wash

  • gullying (fast water runoff)

  • wind erosion

• overgrazing

• deforestation

• unsustainable agriculture

3 common issues caused by soil degradation

• organic matter alteration

• inorganic matter depletion

• toxin buildup

8 types of farming systems

subsistence farming: the production of food by farmers for their own families or the local community

commercial farming: takes place on a large, profit-making scale with the aim of maximising yields

cash cropping: growing crops for the market, not to eat yourself

extensive farming: uses more land with a lower density of stock, which has lower inputs and outputs

intensive farming: uses land more intensively with high levels of input and output per unit area e.g. animal feedlots

pastoral farming: raising animals, usually on grass and land that is not suitable for crops

arable farming: growing crops on good soils to eat directly or to feed to animals

mixed farming: has both crops and animals, it is a system where animal waste is used to fertilise the crops and improve soil structure, and some crops are fed to the animals

reasons for increasing demand for food

• global population growth

• lower death rates and high life expectancy due to better healthcare

• increased levels of wealth leading to higher consumption levels

• growing middle class

reasons some countries are at risk of food insecurity

• political instability/conflict

• quality of infrastructure/technology

• cash cropping in LEDCs e.g. coffee

• limited water access (changing weather patterns from climate change)

• soil fertility

• population density (rapid population growth)

food production in LEDCs versus MEDCs

LEDC food production:

• high levels of export

• big impacts of climate change

• crops are generated for cash

• increasing demand for bio-fuel crops

• low level of technology

• labour intensive process

• corrupt government

• weather limitations

MEDC food production:

• high levels of technology

• high rates of production

• production is maximised through the use of fertilisers, pesticides and antibiotics

• domestic support and subsidies which make LEDC products uncompetitive

• high capital

• modern transport allowing for importing

• less seasonal foods

3 types of malnutrition

under-nourishment: lacking calories

over-nourishment: too many calories leading to obesity

unbalanced diet: the wrong proportion of micro-nutrients e.g. protein

effects of malnutrition on economic growth

• children cannot go to school which damages education level and productivity of population

• stress on healthcare from diseases such as malaria and HIV

• requires investment from government in healthcare, agriculture and infrastructure

factors that influence the choice of food that a place grows and eats

• climate and local ecological conditions

• culture and religion

• politics (governments can subsidise or put tariffs on food to encourage or discourage their production)

• socio-economics (market forces determine supply and demand)

ways to measure the efficiency of a farming system and the farming’s energy budget

1. energy contained within the crop of harvested product per unit area

→ compare the relative energy returns from different crops e.g. wheat or corn, beef or lamb

2. efficiency of the agricultural system

→ the balance between inputs and outputs

ways to improve the sustainability of food supplies and food production systems

• improve technology e.g. trickle irrigation to waste less water

• alter what is grown and how it is grown e.g. GMOs

• reduce food waste by improving storage and distribution e.g. reducing unnecessary consumption of food in MEDCs

• change attitudes towards food and diets e.g. eating less meat

• reduce food processing, packaging and transport

terrestrial versus aquatic food production systems energy efficiency

terrestrial food production systems

• food is harvested at the first (crops) or second trophic level (meat) meaning that it makes efficient use of solar energy

• these systems do have higher losses when it comes to skeletal waste (land-based animals have more energy in their skeletons)

aquatic food production systems:

• food comes from higher trophic levels (trophic level 4+) meaning the energy efficiency is lower than terrestrial systems

• the initial intake of solar energy is less efficient and energy losses in the form of heat are higher in water than on land

two types of processes that cause soil degradation

• processes that take away the soil (erosion)

  → no or little vegetation on soil

  → wind or water eroding the soil e.g. flooding

• processes that make soil less suitable for use

  → loss of nutrients (leaching into water)

  → harmful addition of chemicals/nutrients (pollution)

human activities that lead to soil degradation

• overgrazing

• deforestation

• unsustainable agriculture techniques e.g. excessive use of pesticides

• monoculture

• industry and infrastructure

• urbanisation

• increased sea levels causing flooding and salinisation

three major processes of soil erosion

if soil lacks natural cover/vegetation it can become prone to erosion due to lack of absorption of water, protection from leaves and roots that hold soil together

1. sheet wash: large areas of surface soil are washed away during heavy rain or landslides in mountainous areas

2. gullying: channels develop on hillsides following rainfall which will get deeper over time

3. wind erosion: on drier soils high winds continually remove the surface layer

measures to conserve soil and soil nutrients

• crop rotation to prevent soil degradation, pest and disease build-up

• planting trees or building fences for less wind erosion

• addition of soil conditioners e.g. limestone to improve decomposition by soil microorganisms

• improved irrigation techniques

• soil conservation cultivation techniques e.g. plowing to increase drainage or terracing (rice fields) to reduce steepness of slopes

• stop plowing marginal lands (stop using poor land to grow crops)