Studied by 7 people
Explain how Over Grazing can cause soil degradation + real life example
Too many animals grazing in the same area
Plants cannot recover
Leads to bare patches with no plants
If plants do survive their roots never develop properly as a result --> unhealthy plants
Seen in Sahel Africa (south of Sahara)
o Wealth determined by the number of cattle someone owns --> high levels of cattle stock --> quality of soil dropping --> plants unable to develop
o Drought worsened it
o Cattle died --> massive famine
Explain how Over Cropping can cause soil degradation + real life example
Plant too many crops --> deplete soil nutrients
Makes the soil friable (dry and susceptible to be blown away by wind --> wind erosion)
Nutrients are not restored
Increased risk of crop failure then wind erosion
Seen in Dust Bowl in 1930s America
o Overuse of land led to wind erosion --> wind with dust and soil travelled thousand km
Explain how Deforestation can cause soil degradation
Removal of vegetation --> exposure of soil
High levels of precipitation (Tropical rainforests) --> a LOT of water erosion --> minerals leave that area --> soil unfertilized
No more trees --> leaves unable to slow down rain + roots no longer there to bind soil --> MORE water erosion
Give 3 unsustainable agricultural techniques
Total removal of crops --> leaves bare soil --> more susceptible to erosion (wind/rain)
o + increase in water evaporating --> salinization
- Ploughing in the direction of the slope (hill) --> parallel to water flow --> increase steep channels for water to flow down --> water erosion
- Excessive use of pesticides --> toxification
- Irrigation in poor ways (e.g. spray irrigation) --> Water built up and evaporated instead of absorbed --> leaves behind hard salty layer (salinisation)
- Monocultures --> same nutrients depleted from the soil
Sheet Wash
Large areas of surface soil are washed away during heavy rain
Can include land slides
Gullying
Channels develop on hillsides due to rainfall and get deeper and deeper over time (steeper and steeper)
Wind Erosion
Drier soils are removed by the wind
Top layers consistently removed
How can lime improve soil quality
Lime = soil conditioner
- Neutralises acid soils --> increase pH
--> help clay particles to stick together so they act more like sand and allow more drainage and trap more air into the soil --> increases decomposition --> more nutrients
Why do some soils become acidic?
-Acid precipitation (acid rain)
- Breakdown of organic matter
o Microbes respire to release CO2 --> dissolved with water --> carbonic acid
- Nitrification of ammonium to nitrate --> releases acid
- Leaching of base/alkali ions --> soil more acidic
How can we reduce wind erosion of soil?
- Wind reduction – reduced wind to reduce wind erosion
o Planting trees and hedges to reduce wind --> blocks wind AND increases soil stability (plant roots hold soil together)
How does Terracing reduce soil erosion
- Reduce steepness of hills
o Prevent slope erosion (distributing water more or less evenly as it flows to lower platforms when top ones are full instead of flowing all the way down)
o Reduce soil erosion --> reduces velocity of water
How does Contour Farming reduce soil erosion
- Plough along the slope
- Perpendicular to the flow of water instead of parallel --> slows down runoff water
--> allow water to soak into soil
--> less soil erosion
How does Ploughing reduce soil erosion
- Increase drainage --> more oxygen in the soil --> higher quality soil
How can irrigation be made more sustainable?
- Instead of using spray irrigation (water is not fully absorbed and is built up) --> use other methods --> reduce evaporation --> less salinisation
o e.g. Covering irrigated fields
Reduces evaporation
IF water evaporates --> caught and dripped back into soil
o Trickle flow irrigation
Pipes with tiny holes
Closer down to the soil
Why is crop rotation useful to maintain soil fertility?
o Unlike monoculture where one mineral is constantly being depleted
o Grow legumes --> nitrogen plants (takes nitrogen from air using bacteria and adding nitrogen to soil --> better soil quality)
o Can manipulate crops and let crops produce the minerals needed for other crops to grow (cycle)
What is crop rotation
grow different crops over different years, they will each take different minerals from the soil
Why is soil an essential ecosystem?
-All food grows from soil
- A Habitat for organisms
- Water storage/filter (as water percolates through it)
- Impacts atmosphere temperature --> impacts of heat transfer through it
What 4 main things do soil contain?
- Minerals found in rocks/soil
- Organic material called humus
- Gases (air in soil grains)
- Water (in air spaces)
What is the pedosphere?
Thin bridge between biosphere and lithosphere
Inputs of the soil system.
- Organic material (leaves decay into soil, dead animals/organisms)
- Energy from the sun
- Precipitation
Give one output of the soil system.
- Soil erosion allows materials to leave
- Release heat back into atmosphere
Transfers of soil system
translocation and leaching (minerals dissolved in water and move through soil)
Transformation of soil system
Decomposition
Why are rocks in soil important
o Insoluble parts (e.g. gravel, clay, sand, silt)
o Soluble parts (e.g. mineral salts, compounds of nitrogen)
- Useful?
o Provides the skeleton of the soil and hold the soil together (insoluble bits)
o Soluble’s can be released into the environment which can be used in the ecosystem
o Bedrock underneath all the rock which holds the ecosystem in place
Why is humus in soil important?
o Dead organic matter in the process of decomposition --> gives soil a dark colour
o As it breaks down --> returns mineral nutrients back into the soil (mineral recycling) --> plants can absorb it back into the food chain
o Absorbs and stores a huge amount of water
Why is water in soil important?
o Either moves through the soil OR stored in the soil
o Seeping down from precipitation or moving up from underground sources by capillary action
o Allows movement of dissolved minerals salt in the soil so it is available for plants to uptake
o Rapid downward movement of water --> leaching of minerals (moving minerals from one place to another)
Why may water be bad for soil?
o Rapid upward movement (evaporation) can cause salinisation
o Large volumes of water --> waterlogging which leads to anoxic conditions and acidization
Why are Organisms important in soil?
--> invertebrates break down large particles of dead organic matter --> decomposed by soil microorganisms to recycle mineral nutrients
--> large soil animals (e.g. moles) help burrow and mix to aerate soil
What is a horizon?
A distinctive zone visible in the soil
O Horizon
(Organic Layer) --> New deposited organic matter is started to become decomposed by fungus and bacteria (aka HUMUS)
A Horizon
(Topsoil) --> Build-up of humus, partially decomposed organic material (more than O Horizon), brown colour (humus layer), waterlogged soils form peat (when decomposition is incomplete) as not enough O2 for decomposers to respire --> reduced decomposition
B Horizon
Subsoil) --> Layer where soluble materials from organic matter above is deposited here (e.g. clay and iron salts)
C Horizon
(Parent Rock) --> Partially weathered rock which forms soil
R Horizon
(Bed Rock) --> Unweathered parental rock which holds ecosystem in a place
Name all the horizons in order
O (organic), A(top soil), B(subsoil), C(parent rock), R(Bed rock)
Clay size and properties
Clay size: Less than 0.002 mm
Properties: Wet sticky soil which can be rolled into a ball easily
Silt size and properties
Silt size: 0.002 - 0.05mm
Properties: Wet talcum/baby powder, holds together better than sand
Sand size and properties
Sand: 0.05 - 2mm
Properties: Gritty and falls apart easily
What is loam?
Contains equal quantities of sand, clay and silt soil types
Why is loam so good to grow crops?
- Sand ensures good drainage and good air supply (soil particles aren't close together --> lots of air spaces)
- Silt holds the sand and clay together and make soil easier to work with
- Clay retains the nutrients (has micropores between particles which holds on to nutrients)
Define Porosity and Permeability
Porosity: The air spaces between the particles
Permeability: The ease at which wases and liquids can pass through the soil
What properties does clay have and why? (porosity +permeability)
High porosity = lots of micropores
- Low permeability
o Micropores too small to allow the flow of water through
o Water can be stored
o High level of nutrients retained there but plants can’t get to them (minerals are locked in clays)
- Micropores holds small amount of water --> hydrogen ions in water bond to clay particles and is removed from water --> high conc of hydroxide ions in water --> causes an acidic pH --> build-up of minerals
- Therefore... Rich soil with low fertility
17. What properties does sandy soil have and why?
- High porosity = macropores
o Water can collect
- High permeability
o Large macropores allow water to percolate through easier
Why does acidic pH decrease soil fertility?
o Lower pH --> increase solubility of essential nutrients (e.g. calcium and magnesium) in water --> leaching/run off --> plants cannot access
- Toxification
- Reduce microbial diversity and activity
Commercial agriculture vs subsistence farming
- Commerical agriculture = large scale production of crops and livestock to be sold for profit
- Subsistence agriculture = farming for self-sufficiency to grow enough for a family or villages only
Define malnutrition and its 3 types
- Malnutrition = Unbalanced diet
o Undernourishment = lacking calories
o Over nourishment = too many calories leading to obesity
o Unbalanced = wrong proportion of micro-nutrients
Why do people in MEDCs get malnutrition? How does this differ in LEDC?
- MEDCS have relatively cheap food prices --> Over nourishment
o Purchase based on choice rather nutritional need
o Less seasonal variation due to food coming from imports
o Bad education and choices --> lack or too much of certain food groups
- LEDS have relatively high food prices
o Purchase based on need
o Political and commercial pressures may mean food exported rather given to home population (cash cropping) --> not enough food for population --> undernourishment
Why has food production increased since the 1960s?
We can grow 23% more food than 1961 due to technology --> Not because of food availability Instead... Lack of distribution
Why is growing livestock a useful way of gaining protein?
- Useful way to convert unsuitable plant material for human digestion --> valuable protein
o We can't eat grass (don't have the enzyme to break it down) --> cows can eat grass --> eat the cow
What does arable farming mean and how is this different from a natural ecosystem?
- Arable farming = growing crops
o Deliberately sow seeds into soil cleared of natural vegetation and then plant one type of crop (monoculture)
o Fertilisers added to increase growth rate
o Harvesting = removal of biomass from soil and ecosystem
Differs? : Reduces soil fertility over time! (Plants aren’t decomposing --> not returning the soil nutrients back into the soil)
Measuring efficiency of farming systems and give two examples
Comparing the relative energy returns from different crops
o Measure inputs and outputs of energy for each crop
BUT you must look at quality of energy (need to eat lots of cereal to get the same amount of energy as pork)
- Dairying/ Horticulture (Western Netherlands)
o Intensive commercial
o Inputs: high labour and technology
o Outputs: high per hectare and per farmer
o Efficiency: high
o Environmental impact: high due to greenhouses for salads and flowers are constantly heated, dairying (grass is fertilises, cows produce waste)
- Rice Growing (Ganges Valley)
o Intensive Subsistence
o Input: high labour and low technology
o Output: High per hectare, low per farmer
o Efficiency: high
o Enviornmental impact: low (Padi rice has polyculture which can benefit each other e.g. fish and rice crops, grow other crops which increase variation)
Traditional extensive agriculture
limited selective breeding, no genetically engineered organisms, polyculture, small effect on biodiversity, little soil erosion
Intensive agriculture
strong selective breeding, genetically engineered organisms, monoculture, reduction in biodiversity, strong soil erosion
How is Borneo’s rice production more efficient compared to California more intensive farming of rice?
Borneo – traditional
o Inputs
§ High labour
§ Energy and chemical inputs are low (no machineries use, petrol, gas)
o Output
o Low output + low input = Very efficient as a system
- California – intensive
o Inputs
§ Low labour
§ High energy and chemical inputs
o Outputs
§ High output as a result of inputs
o Input more energy than taken out --> energy not as efficient as Borneo
§ Commerical use of fertiliser and diesel in California --> pollution --> less sustainable
Why is aquaculture less efficient for human consumption compared to terrestrial farming?
- Terrestrial (on land where sunlight is readily available)
o First or second stage of food chain (crops or animals that eat the crops)
o Efficient use of solar energy transfers
o BUT! Still losses in terms of energy (e.g. skeletons not digestible and passed on to humans)
- Aquatic
o Later trophic levels in food chains (e.g. Carnivorous fish level 4)
§ At this point lots of energy has been lost!
o Low efficiency of energy
o More energy is lost as heat as water is a good conductor instead of being turned into biomass
What methods can we use to increase food production? (how to maximise yield sustainably?)
tech, alter, green, reduction
Improve Technology:
- Mixed cropping (different crops in the same fields) to conserve water
- Buffer zones where there no crops to avoid runoffs (e.g. water is caught by trees)
- Biological controls rather than pesticides
- Trickle irrigation rather than spraying
Altering of Crops:
- Genetically modified crops (resistant to droughts, grow quicker, resistant to diseases) --> don’t need to use as much fertiliser
- Legumes (beans and peas) have bacteria called rhizobium that aborbs atmospheric nitrogen and replenish the nitrogen in the soil
- Hydroponics (water plants that just require water and can even be grown indoors --> less soil)
- Aquaculture (fisheries rather than catching wild fish)
Green Revolution:
- Agroecology – make farms a closed system (maintain itself) and recycle nutrients balancing animals and plants (less fertiliser needed)
- Grow plants resistant to droughts (less water needed)
- Methods to preserve soil
Reduction of food waste:
- LEDCS – fix production problems and storage problems
- MEDCS – fix consumption (eat too much or put too much on waste and waste food when not finished, expiry dates)
- Governments can monitor and control
Change attitudes towards food and diet
§ Eat new crops
§ Eat less meat --> insects instead
§ Increase education --> waste less food
§ Reduce food processing
How is our food consumption prediction to change over the next 10 years? (2030)
- Human population will be above 8 billion (already happened in 2022)
- Human calorie consumption in MEDCS will hit 3000 per day
- Number of people who suffer from hunger will fall but at unequal rates globally
- More people will eat more meat
- An extra billion tons of cereal will be needed
- Increased yield will come from technology and irrigation not more land
- GM will increase improve pest control and increase survival of crops in harsher conditions globally
- Aquaculture will increase
