Soil systems Flashcards
what is soil
made up of minerals, organic material, gases and liquid
what does soil do
- plants grow in soil
- soil is habitat for many organisms
- soils hold water and mineral nutrients
- soils store and transfer heat
soil consists of
- rock particles
- plant and matter in process of decomposition
- water
- air
- soil organisms
soil horizons (layers)
O horizon - newly added organic material
A horizon - where humus builds up and is mixed up with fine material particles
B horizon - where soluble minerals and organic matter is deposited
C horizon - mainly weathered rock
sandy soils
gritty and fall apart easilty
silty soils
slippery when wet and hold together
clay soil
feels sticky and can be rolled into ball easily
loam soil
- good for agriculture
- sand particles ensure good drainage
- clay retains water
- silt particles help hold sand and clay particles together
subsistence farming
- the provision of food by farmers for their own families or local community
- low inputs of energy in the form of fossil fuels or chemicals
- vulnerable to food shortages
commercial farming
- large profit making scale
- high levels of technology, energy and chemical input
- uses more land with a lower density of crops
pastoral farming
- raising animals on land not suitable for crops
- uses large amounts of land
arable farming
- growing crops on good soils
- primarily to eat or feed animals
malnutrition
raising animals on land not suitable for crops
factors affecting food choices
- climate - determines what grows where on earth
- political - governments can put subsidies or put tariffs on food
- social and economic - market forces determine supply and demand
terrestrial food systems
- food is usually harvested at first and second trophic level
- therefore production systems make efficient use of solar energy
- have higher losses coming to skeletal waste
aquatic food systems
- food comes from higher trophic levels
- energy efficieny is lower than terrestrial
- energy losses in heat are higher
how to increase sustainability of food supplies
improving technology - mixed cropping, buffer zones, pest control
altering what we grow - gm food doesnt need pesticides, soil conservation, reduce food waste
prediction for future food supplies
- human population will grow to 8 billion by 2030
- calorie consumption increasing to 3000kcal per person
- numbers of hungry people will decrease to 400 million
- GM crops increase productivity
processes that lead to degradation
- overgrazing
- deforestation
- unsustainable agriculture`
overgrazing
- when too many animals graze in the same area
- leaves bare patches of soil which are removed by wind and rain
- takes many years for region to recover
overcropping
- depletes soil nutrients
- reduces soil fertility
- crops more prone to failure
deforestation
- removal of forest
- the more vegetation removed, the more prone to erosion
soil cultivation techniques
- cover crops between rows of main crops keeps soil in place
- plowing breaks up soil structure and increases drainage
- contour farming plows along cultivation lines, reducing erosion
