Unit 5 (Kognity only) Flashcards
Why is soul vital for human wellbeing?
Required for food production, essential in the nutrient cycle, carbon sink, filters water
Soil contains
Micro-organisms of bacteria and fungi
Loss of vegetation results in
Soil surface to be exposed allowing it to be swept away by wind and water
Soil loss and degradation affects
Globally to both developed and developing countries
Souls are important since….
They provide a medium for plants to anchor themselves, they recycle matter, and are integral to nutrient cycles such as the nitrogen and carbon cycle
Ecological succession occurs….
Over time and results in changes to the soil fertility
Soil is considered to be
A non-renewable resource although it is constantly formed
Fertile souls provide
The conditions required for seed germination and growth
Soils which provide a good growing medium for plants contain:
Organic matter, nutrients and minerals, sustainable pH level (close to neutral)
Ideal pH for soil
Close to neural (5.5-7.5). It affects availability of nutrients and minerals for plant uptake. If too acidic, it will release toxic aluminium ions
Soil nutrients
Nitrates, phosphates, potassium compounds
Soil minerals
Sulphur, calcium, magnesium, iron, manganese, boron, copper, zinc, and molybdenum compounds
A healthy soil community
Breaks down organic matter and returns nutrients back to the soil
Organic matter provides for soil…
Moisture holding capacity, and good structure
Good soil structure provides
Sufficient drainage to prevent water logging
The climax community and associated soil ecosystem will
Vary within places depending on climate and bedrock
Primary succession involves:
The development of a community from bare rock with no soil to a climax community with mature soil that contains organic matter and processes good water, nutrient retention capacity, and good structure
Step 1 of soil succession process
Bone rock is exposed die to a disturbance, no soil is present (retreating glacier or organic eruption etc)
Step 2 of soil succession process
Pioneer species like lichens and mosses establish themselves in the rock substrate
Substrate
Underlying substance or layer, the surface or material on or from which an organism lives, grows or obtains it’s nourishment.
Step 3 of soil succession process
Pioneer species die and decay providing soil and nutrients for other plant species like shrubs and small trees
Pioneer species
species first to colonise disrupted or damaged ecosystems, beginning a chain of succession that leads to a more biodiverse steady-state ecosystem
Step 4 of soil succession process
Small and large trees begin to grow and the community reaches an equilibrium or balance, resulting in a climax community
Biological activity within the soil contributes to
Mineralisation of feed organic matter (waste matter / dead organisms) which increases nutrient levels
The decomposition process involves
Invertebrates such as earthworms and woodlice, fungi and bacteria
Invertebrates such as earthworks and woodlice
Mix some organic matter into the soil making it available to other organisms including residential bacteria and fungi. This also aerated the soil. They also feed off and digest the organic matter resulting waste products are further broken down by bacteria
Fungi and bacteria
Break the organic matter down and release them into the soil
Nitrogen fixing bacteria…
Absorbs nitrogen gas from air and transforms it into nitrites (nitrogen cycle)
Soil fertility is enhanced by….
Fertilisers which increase soil nutrient levels
Rate of soil formation
The FAO estimate that it takes around 1000 years to develop 5cm, depending on the location and climate
Ideal conditions for soil formation
Sunny, warm, and wet where there is maximum plant growth. This contributes to high levels of plant litter and other dead organic matter to break down.
NON ideal conditions for soil formation
Soil formation is slow under cold and/or dry conditions which is where formation mag occur at 1mm per 1000 years
The rate of global soil degradation is
Much faster than the rate of soil formation
Soil is considered non renewable because
It is not replaceable within a human lifespan or at a pace faster than at which it is used
For soil to be sustainable
We must reduce loss and degradation rate and improve formation rates
A 3rd of the world’s soils
Are degraded. The majority of global degradation is caused by erosion
Process involved with soil loss and degradation
Water erosion, wind erosion, chemical degradation (salinisation, acidification, nutrient depletion, and chemical pollution), physical degradation (soil compaction)
Erosion
Solid particles transported from one place to another by water or wind, removing the fertile top soil.
The loss of organic matter….
Leads to a reduction in water retention capacity
If eroded soil enters watercourses….
Sediment can clog up ditches, reduce the capacity of water courses and increase risk of flooding. Soil particles rich in nutrients and pesticides cause water pollution
Negative of removing sediment
Removing this sediment by dredging is an expensive process.
3 phases of water erosion
Detachment, transport, deposition
Water erosion - detachment
When raindrops hit soil, it frees some soil particles, then run off detaches more soil particles as it flows
Water erosion- transport
The flow of the water carries the soil particles
Water erosion - deposition
When the water slows down, the particles are deposited
Types of soil erosion occur….
As a consequence of the action of water including sheet erosion, till erosion, and gully erosion
Areas most vulnerable to wind erosion
Dry regions with exposed soil surfaces since the wind picks up the soil and carries it through the air. Light and lose particles (eg: sand) are more easily picked up.
Wind velocity increases
Along large and flat areas making large open areas more vulnerable than small areas with trees and shrubs that provide soil coverage and act as wind breaks
Further impacts of wind erosion include:
Soil particles damaging plants within their wind path, reduce visibility and can cause build up of soil deposits on roads and surfaces
Chemical degradation (soil fertility reduction) methods
Salinisation, acidification, nutrient depletion, chemical pollution
Chemical degradation - salinisation
Occurs when water evaporates and leaves salt, the salt accumulates and soil becomes saline. Fruit and vegetables can’t grow in saline soil. This issue is most severe in arid and heavy irrigated areas due to high evaporation levels
Chemical degradation- Acidification
Occurs with an increase in hydrogen ion concentration lowering pH. This can be caused by acid deposition, leaching, and removal of nutrients from the soil ecosystem and use of ammonium based fertiliser. The latter is converted by bacteria in the soil to form nitrate and hydrogen ions. The nitrates can be either taken up by plats or leached from the soil
Chemical degradation - nutrient depletion
Caused by over exploitation (eg: continual cropping without replacing nutrients) loss of fertility reduces the capacity of the soil to support further plants. Artificial fertiliser does not always contain all nutrients required for healthy plant growth
Chemical degradation - chemical pollution
Eg: The accumulation of toxic metals within soils from the use of pesticides (eg: Bordeaux mixture a fungicide used on fruit can result in the accumulation of copper in soils)
Physical degradation
Including soil compaction, from use of heavy farming machinery and animals. When the soils became compressed, air spaces between the particles are lost. Reducing porosity and the soil may be more easily waterlogged, difficult for plant root systems to penetrate. A crusty flaky surface my fever that is more vulnerable to water and wind erosion
Human activities that accelerant soil loss and degradation
Urbanisation (loss of soil cover). Overgrazing, deforestation and mismanagement of arable land contributed to soil degradation leading to increased risk of desertification
Threats to soils - Urbanisation
Growth of cities causes loss of soil cover, quality of soil within urban areas varies due to soil movement from place to place. Urban soil suffers from soil pollution and compaction such as from leaded petrol or rubbish. Water and wind erosion can undercut urban structures damaging buildings and roads
Threats to soils - Livestock overgrazing
Excessive vegetation removal by livestock grazing leaves soil exposed to processes of water and wind erosion
Threats to soils - deforestation
Soil is exposed once trees are removed. Lack of vegetation to intercept rainfall reduces water infiltration into soil increasing water run-off. Water erosion of soil results in transfer of organic matter and nutrients from the forest into nearby watercourses causing water pollution. Organic matter contributed to lower dissolved oxygen levels and nitrates can cause Cyanobacteria blooms
Threats to soils - farming
Some farming methods caused soil degradation by exposing the soil to the processes of water and wind erosion through enhancing chemical or physicals degradation
Farming methods employed by commercial farming….
Cause greater soil degradation than small subsistence farming. However, the is variation from one farm to another also depending on soil conservation methods employed
Threats to soils - desertification
In relatively dry land regions, soil loss and degradation can contribute to desertification - the transformation of arable land to desert. The risk is further increased by climate change and associated drought
Desertification leads to….
Loss of food production that could threaten food security and result in famine
Tillage (intensive and sustainable farming)
(Used to prepare soil for sowing) Ploughing the land and clearing any debris can leave the area bare and vulnerable to water and wind erosion
Monoculture (intensive farming)
Extracts specific nutrients from the soil leaving the soil nutrient poor
Growing multiple crops per year (intensive and sometimes subsistence farming)
Removes nutrients at a faster rate than they are being replaced. This results in nutrient deficiencies in the soil. Cultivation of steep slope encourage loss of topsoil due to wind and water erosion
Excessive irrigation (intensive and not subsistence)
With poor drainage can cause water erosion or salinisation
Use of pesticides/chemicals (intensive and only sometimes subsistence)
Use of chemicals and particular pesticides damage the soil microbial community
Marginal areas (intensive and subsistence farming)
Marginal areas not typically suitable for farming without high levels of inputs (fertilisers). Productivity is limited (low soil nutrient levels, poor drainage, difficulty accessing location) eg: a alone and invariable crop production weather. Farming here increases rate of degradation particularly if above is used such as ploughing. Over time crop yields will decline and to survive farmers require more land
Dependent on soils is
95% of global good sources - so soil loss and degradation can threaten food production and security
For farming to be more sustainable, methods to prevent soil loss and degradation need to be placed
Eg: reducing wind and water erosion, salinisation, managing available nutrient levels, limiting grazing, and stopping use of marginal land since it is prone to erosion
Reducing water erosion
Reduces loss of fertile land, decreases risk of flooding downstream and the clogging and pollution of aquatic ecosystems
Methods of reducing water erosion
Vegetation cover can intercept rainfall and reduce soil erosion. Controlling run off limits water erosion by capturing water as it flows. (Eg: terracing along steep hillsides) this can be expensive to maintain and construct but is effective. Buffer strips, increasing infiltration
Buffer strips that are permanent vegetation
Can be located at the edge of a field (grassland/shrub strips that intercept run off) or within the field (grassed warerways which are shallow ditches that divert water)
Increasing infiltration if water into soil by improving soil structure and moisture entente on through….
The addition of organic matter (eg: manure), mulching using materials to cover soil surface reducing evaporation (straw, grass, wood chips), avoiding compaction, conservation tillage where residue from the previous crop is left on the soil surface - reducing wind erosion
Conventional tillage
Soil is physically broken up by ploughing resulting in loose soil which can aerate and moist. It reduces weeds. Residues are ploughed into the soil and the surface of land is cleared of debris
Conservation tillage
Crop residue is left as mulch on the soil surface to increase Infiltration, reduce run off and associated water erosion. No-toll is a form of this where no ploughing occurs
Techniques to reduce wind erosion (and The last 3 also apply to water)
Wind breaks (trend, large shrubs) to reduce velocity and capture blowing soil, buffer strips (also wind breaks), vegetation cover, shelter belts (blocks of trees/shrubs at right angles to deflect wind and reduce velocity), conservation tillage (crop residues on the soil surface to provide protection)
Advantage of wind breaks and shelter belts
The also provide habitats for wildlife and pollinators
Salinisation can be reduced by:
Avoiding over watering, good drainage, no watering at certain time of day (watering at night or late afternoon avoids heat and evaporation)
Excess salts can be removed from soil by….
Flushing them out using water
Nutrients lost to plants….
Need to be replaced and the soil pH may meed to be amended to maintain conditions suitable for crop growth
Nutrient levels in soil can be maintained by:
Addition of organic matter, growing of green manure, synthetic fertilisers, liming, crop rotation
Addition of organic matter
Such as manure, increases organic matter and nutrient levels which improve overall soil structure
Growing of green manure
Eg: leguminous plants (clover, alfalfa, and vetch) also in increases organic content
Liming
Addition of calcium carbonate (limestone) or calcium hydroxide (hydrated lime) raises pH and improves soil capacity to support crops. Low pH levels can reduce available nutrients and mobilise toxic chemicals such as aluminium ions
Crop rotation
Changing the crops grown on a plot each season on a 3-4 year cycle to prevent depletion of particular nutrients and maintain soil fertility
Overgrazing
Reduced by restricting the number of animals and time spent in one area. Areas should not be stripped of vegetation cover. Sufficient time should be given for vegetation to recover before returning live sock. Grassed warerways and wind breaks also minimise potential water/wind erosion
Arable farms
Focus on crops such as corn
Mix farms
Produce both crops and animals
Pastors farms
Focus on rearing animals
Type of farming chosen and levels of food production will be dependent on: (levels of production very around the world)
Environmental conditions, access to vehicles and technology, funds a aisle to purchase land and inputs, cultural and environmental value systems that influence methods, government and Political initiatives
Processes, transfers, and transformations of soil
Leaching, evaporation, decomposition, weathering
Stores of soil
Organic matter, organisms, minerals, air, water, nutrients
Outputs of soil
Soils loses minerals, organic matter, water and gases ???? Check this need clarification
Soil inputs
Minerals, organic matter, gases, water
Layers of soil
Organic layer (O), zone of leaching (A), zone of accumulation (B), weathered parent material (C)
Soil properties
The proportions of sand, silt, and clay
Soil texture and structure have
A very important impact on soils mineral and nutrient content drainage, water holding capacity, air spaces, boots and organic matter retention
Soil texture
The look and feel of the soil, which is linked to the real stove proportions of sand, silt and clay particles
Soil is not
Static, it continuously changes and develops through physical, chemical and biological process, as it processes it can be seen as a system
Minerals
Come from the weathering of parent material. Weathering breakdown parent material by physical, chemical, and biological processes
Organic matter
Comes from the living organisms on and in the soil. Soil and vegetation develop together.
During succession
Early plants colonise the area before the soil has developed. When the early plants die they add organic materials.
Soil is considered an ecosystem as such
it contains living organisms. These organisms are inputs that add organic material to the soil and carry out some of it in the soil forming (pedogenesis) process
Gases
Certain plants also add inputs into the soil, certain plants fix atmospheric nitrogen into nitrates and ammonia compounds in the soil. Nitrogen fixation processes form an input into the soil system. The living component of the soil also respites removing oxygen and adding carbon dioxide
Water
The way water enters depends on whether the soil is in a slope and where it is on the slope. The too received the most water by direct precipitation, lower down the water receives via precipitation but also as through flow from top slope soils
Decomposers
Fungi, age and bacteria are some of the main soil decomposers. They break down the DOM and release plant nutrients. The transformation of organic matter to nutrients gradually increases soil fertility
Sandy soils
Feel gritty, large particles that create large pores spaces between them. Well drained so rarely get water logged, subject to drought in times of low rainfall, warm up quickly in summer due to high air content
Clay soil
Smallest particles providing a sticky feel. Small particles give small pore spaces. Poorly drained and prone to water logging, take a long time to dry out after rainfall, warm up slowly in summer due to high water content
Soil texture is the result of
Parent material and the type of weather
Physical weathering yields
Coarser and textured soils
chemical weathering tends to give
finer textures
No matter what type of weathering takes place
The longer it continues, the smaller the particles
Sile particles are
Too small for the human eye to see and soils high in silt have a smooth feel. The smaller particles give smaller pore spaces so their properties are between sand and clay
