IB ESS Topic 5

soil

a complex ecosystem made up of minerals, organic material, gases and liquids which forms the habitat for many species of plant and animal

soil storages

the energy and matter within soil - organic matter, organisms, nutrients, minerals, air and water

soil transfers

biological mixing, translocation, leaching

translocation

movement of soil particles in suspension (liquid)

leaching

minerals dissolved in water moving through the soil

soil inputs

organic matter from leaf litter and dead or decaying organisms - inorganic matter from parent material (rock), precipitation and energy

soil outputs

uptake by plants (minerals and water)

soil erosion

soil transformation

decomposition or organic material taking place

weathering causes large particles (rocks) to become smaller

nutrient cycling within soil

minerals

metal atoms and compounds which make up rocks - dissolved in water to become an inorganic storage in soils

humus

plant and animal material in the process of decomposition - generally the top layer of soil

soil horizons

the layers of soil in a cross-section which is modified over time as organic material leaches downwards and mineral material moves upwards

O (soil horizon)

leaf litter - newly added organic material

A (soil horizon)

mineral horizon at the surface showing organic matter enrichment - where humus forms

B (soil horizon)

subsoil horizon showing enrichment of clay material, iron aluminum, or organic compounds - where soluble minerals and organic matter tends to be deposited from the layer above

C (soil horizon)

horizons of loosened or unconsolidated material - mainly weathered rock from which soil forms

soil structure

the proportions of clay <0.002mm particles, silt 0.002 - 0.05mm particles, and sand 0.05 - 2mm particles

sandy soils

gritty and fall apart easily - good drainage and air supply to the roots, however, leaching is rapid

clay soils

good nutrient retention, however, heavy soils which are relatively impermeable and have poor drainage

loam soils

roughly 40 - 40 - 20 sand, silt, clay

ideal for agriculture due to sand's drainage and porosity, clay's nutrient retention and silt keeping the other two together

porosity

e.g. high in sand soils, low in clay

the amount of space between particles in soil

permeability

e.g. high in sand soil, low in clay

the ease at which gases and liquids can pass through the soil

infiltration

the penetration of water into the soil

NPK

the most important soil nutrients for plant growth - often leach out or may be removed when plants are harvested

often found in soil fertilisers containing nitrogen, phosphates and potassium (potash)

terrestrial

of the Earth - meaning "land" in ecology

LEDC

less economically developed country - a country with low to moderate industrialisation and low to moderate average GNP per capita

GNP

gross national product - the economic productivity of a country - often give per capita (the average per person)

MEDC

more economically developed country - a highly industrialised country with high average GNP per capita

agribusiness

the business of agriculture production including farming, seed supply, breeding, chemicals for agriculture, machinery, food harvesting, distribution, processing and storage

commercial agriculture/farming

large scale production of crops and livestock for sale

subsistence agriculture/farming

farming for self-sufficiency to grow enough for a family

cash cropping

growing crops for the market

extensive farming

farming using more land with a lower density of stocking or planting and lower inputs = lower outputs

intensive farminng

farming using land more intensively with high levels of input and output per area

pastoral farming

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

arable farming

growing crops on good land to be eaten directly, or to be fed to animals

mixed farming

farming of both crops and animals - animal waste may be used as fertiliser and to improve soil quality, and some crops are used to feed animals

malnutrition

"bad nutrition" - a diet which is unbalanced (may be too much or not enough of a particular nutrient(s)

grain production

provide half the human population's calories (energy)

climate (food choices)

determines what will grow where on Earth

can be adapted through irrigation and using greenhouses to artificially alter

irrigation

the supply of water for crops other than natural process such as rain or water tables

cultural and religious (food choices)

some people only eat certain foods/avoid certain foods due to their beliefs or traditions

political (food choices)

governments may subsidise or tax some foods to encourage or discourage their production

e.g. the EU manipulates food production in this way

socio-economic (food choices)

market forces determine supply and demand

e.g. high profit crop + high demand > more farmers decide to produce this crop > supply increases > profit decreases > farmers move to a different crop > supply drops...

biofuel

living plants converted to fuel to replace fossil fuels

bush meat

any wild animal killed for food (sometimes "game")

a controversial term as it often brings to mind in many parts of the world where the bush meat may be under threat of endangerment e.g. harvesting of apes leading to orphaned young :'(

animal domestication

the use and keeping of animals for human purposes - occured a long time before humans started cereal farming

first dogs, then sheep, cattle, pigs

livestock

animals in pastoral farming - useful in converting plants which humans cannot digest (grass) into valuable protein

monoculture farming

a single species of plant grown on a farm, usually in high density

harvesting

the removal of biomass from the field, soil and ecosystem - results in a loss of quality of the soil as nutrient which would have been recycled back into the soil are removed (and must be replaced)

crop rotation

a way to reduce the loss of soil fertility - leguminous crops (soya beans, peas and other beans) are grown every fourth year as they are able to fix their own nitrogen, and so add it back into the soil

palm oil

a tropical palm tree from West Africa and Central America, imported to South East Asia

demand for palm oil in many food, cosmetic, lubricant and biofuel products is the most significant cause of rainforest loss in Indonesia and Malaysia

shifting cultivation (comparison of farming systems)

e.g. Amazon rainforest

extensive subsistence farming

low inputs - manual labour and hand tools

high efficiency

low environmental impact (only if enough land to move to - forest is given time to regrow)

cereal growing (comparison of farming systems)

e.g. Canadian Prairies

extensive commercial farming

inputs - high use of technology and fertilisers

low outputs per area (hectare) but high per farmer/farm

medium efficiency

high environmental impact - loss of natural ecosystems, soil erosion, loss of biodiveristy

rice growing

e.g. Ganges Valley

intensive subsistence farming

inputs - high labour, low technology

high per area (hectare) outputs, low per farmer

high efficiency

low environmental impact - padi rice has a polyculture (many species supported), often stocked with fish - may grow other crops concurrently

farming's energy budget

the energy of a farming system

may be measured as:

- energy contained in the crop of product per unit area

- efficiency of the system (the energy inputs compared to the outputs) = a more scientific and honest look at energy usage in a farming system

agro-ecology

where nutrients and energy are recycled on farms within a closed system with crops and animals balancing inputs and outputs

genetically modified (GM) crops

may have DNA inserted from another species to provide a benefit from the other species

PROS

may increase disease resistance

can be enhanced to contain extra nutrients

may increase yield

CONS

generally surrounded by concerns on safety, ethics and environmental concerns

soil degradation

possibly one of the most pressing environmental and social problems facing society today

generally caused by soil erosion and/or reduction in soil's suitability for use

soil erosion

the process of soil being taken away

overgrazing

too many animals graze (eat grass/plants) in the same area - results in bare patches of soil where roots no longer hold the soil together leaving it open to soil erosion from wind and rain

overcropping

too many crops being used in an area of land without a break or crop rotation - results in reduction of soil fertility as no nutrients are being returned to the soil

deforestation

the removal of trees which often results in soil being left exposed, leading to soil erosion

urbanisation

the creation of cities - land is paved and built upon causing increased run-off and probably increasing soil erosion elsewhere

soil conservation

improving the soil - reducing erosion and conserving nutrients

addition of soil conditioners (soil conservation)

e.g. lime and organic material - used to increase soil pH and counteract acidification (from acid deposition and soil processes)

wind reduction (soil conservation)

planting trees or bushes between fields (shelter belts) or by alternating low and high crops in adjacent fields - reducing wind action on soils = reduced wind ersion

cover crops (soil conservation)

use of fast growing crops between harvesting of main crops to ensure bare soil is not exposed for too long

terracing (soil conservation)

terraces reduce the steepness of slopes by replacing the slopes with a series of horizontal terraces separated by walls - common in Asian wet rice fields = reduces run-off

reduced plowing (soil conservation)

traditionally the top layer of soil is broken up in Autumn - this damages soil as it breaks up the soil structure and disrupts microbial activity

alternatives are no tillage and direct seed drilling

improved irrigation (soil conservation)

careful planning and construction of irrigation systems can reduce evaporation and therefore salinisation

e.g. drip irrigation (trickle irrigation) - uses a series of pipes throughout a field to add water slowly = less evaporation

salinization (soil degradation)

the increase in salt levels of soil due to water evaporation leaving salts and chemicals behind

What is soil made from?

mineral particles, organic remains, water, and air