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5.3 Soil Degradation and Conservation - Coggle Diagram
5.3 Soil Degradation and Conservation
Soil Ecosystems change through succession
Fertile soils contains a community of organisms that work to maintain functioning nutrient cycles and that are resistant to soil erosion
Community or organisms: tree, bacterias, fungi, earthworms, decomposers, other soil organisms, faeces
Relationship between soil ecosystem succession and soil fertility
Influence biotic factors range from organism or bacteria to humans
Bacteria fix atmospheric nitrogen converting into a usable form for plant roots
Mycorrhizal fungi on tree roots take up soil nutrients and pass them directly to the tree
Decomposers break down litter releasing nutrients into the soil
Soil organisms help to mix the soil improving its structure
Animal faeces aerate the soil
Animal faeces return nutrient to soil
Indirect Influence
Interception of precipitation by vegetation
Reduction of precipitation via evapotranspiration
Soil Degradation
Erosion by water and wind
Physical Degradation
Chemical Degradation
Biological Degradation
Climate and land use change may accelerate the above factors
Physical Degradation
Loss of structure, soil crusting, surface sealing and compaction
Caused by compaction through heavy machine or animal and cultivation in wet weather
Soil crusting and compaction ;- increase runoff, decrease the infiltration of water into soil, inhibit plant growth and leave the surface bare
Factors Influencing the erosion of soil by water and wind
Water
Rainfall intensity and run off
Soil Erodibility
Slope Gradient and length
Vegetation
Wind
Soil Erodibility
Soil surface and roughness
Climate
Unsheltered Distance
Vegetation cover
Human activities can reduce soil fertility
Degradation
Removal of some or all cover of trees
The greater the % of tree removed, the less interception occurs, the more soil compaction by raindrop impact, increase soil erosion potential
Rate of erosion are high in semi arid areas
Intensive Grazing
Overgrazing ;- Grazing of natural pastures at stocking intensities above the livestock carrying capacity
Main Impacts
More vege cover removed
Reduce interception, increase raindrop impact and soil erosion
Increase soil compaction, less infiltration, soil becomes impermeable
Urbanization
Requires removal of vegetation for construction and heavy machinery, compacting soil surface
Soil impermeable, cannot infiltrate
Increase runoff
more topsoil removed
Irrigation
Increasing amount of salt in soil
Evaporation, leaves behind salt
Monoculture
Commercial system
Deforestation, leaves soil bare, soil erosion
Lead to soil exhaustion, reduce availability of certain nutrients
Ploughing lead to soil erosion
Lost nutrients replaced by fertilizer costly
Use of pesticides, soil toxification
Impact for reducing soil fertility
Soil erosion
Major process of soil erosion exist
Sheet wash
Large areas of surface soil are washed away during heaving rain (can include landslide)
Gullying
Channels develop on hillsides following rainfall. Over time they get deeper and deeper
Wind erosion
Drier soils have the top layers consistently removed
by wind/ water
type of erosion: surface, gully, rill and runnel erosion (sink hole)
Toxification
Caused by municipal and industrial waste, oil spills, excessive use of fertilisers, herbicides and insecticides or release of radioactive materials and by airborne pollutants
Salinization
Found in marine derived sediments, coastal location
Hot arid areas where capillary action bring salts to the upper part of soil
Removal of vegetation in dry land farming
Desertification
The spread of desert-like conditions into previously green areas causing a long-term decline in biological productivity
Caused by climate change and/or by destructive use of the land
Reduced soil cover through grazing or preparing soil for planting increase wind and water erosion
Reducing soil nutrient and damaging soil structure
Commercial industrialized food production systems
reduce soil fertility more
than small-scale subsistence farming methods
Commercialized FPS
How it reduce soil fertility?
Alter natural environment / deforestration. Deteriorates soil quality & eliminates biodiversity.
Fields have also become larger to allow greater & easier use of machinery, so more land is lost.
Deforestation for oil palm plantation
Use of heavy machine compact the soil → more
impermeable → reduce O2 content.
Use of fertilizer alter soil’s chemical composition + increase nutrient runoff
Use pesticides / herbicides → increase amount of dangerous toxins → in the long run make soil too toxic for further agricultural use
(toxification)
Large amount of chemical and energy input is required
Goal: maximize the yield of crops to achieve economies of scale.
Why people consume? = It's mass produced, so it's cheaper
Case Study - Commercial farming in East Anglia, UK
It's an area of intensive arable farming, with large open fields and heavy use of agricultural chemicals.
Impact: The previously fertile soil is much depleted and requires further use of fertilizers for commercial crops to be grown successfully.
Options for soil conservation:
avoid inappropriate weather conditions (e.g. heavy rain) for ploughing and harvesting
add organic matter to the soil to increase water retention
add clay to the soil to improve soil cohesion
practise crop rotation so that soils do not become exhausted (this is less common now due to specialization in farming)
use wind breaks to reduce the risk of wind erosion
use cover crops to protect the soil in winter
mulching - plough in the remains of the previous season's crop to improve nutrient retention in the soil
leave some land fallow so that it can improve its fertility.
Subsistence farming
More holistic approach to farming by relying on ecological processes, biodiversity & cycles adapted to local conditions
Sustainable
Grow range of crops, improve biodiversity. Makes farm less susceptible to pests, less pesticide required
Rely on more natural fertilizer. e.g. manure, compost
Less use of machinery
But why is small-scale farms declining?
Don't produce large amounts of food
More expensive compared to mass-produced harvests
Limit of fund compared to commercial
Struggle to get products to market place
