Agriculture and the Environment Flashcards
Define soil
Outer, loose layer that is found just below the surface of the earth
Soil Composition
- Inorganic material particles- 45%
- Organic matter- 5%
- Water- 25%
- Air- 25%
Characteristics of Clay
Less than 0.002 mm
Holds a high proportion of water due to the capillary attraction of the tiny spaces between its small particles- called a ‘heavy’ soil
Drains slowly
Takes longer to warm up in spring
Becomes hard and cracks during summer or dry periods
Characteristics of Silt
0.002-0.05 mm
Well drained
Hold more moisture than sandy soils
Easily compacted when wet
Characteristics of Sand
0.05-2 mm
Water drains through it easily- ‘light soil’
Warms up quicker than clay
Dries out quickly
Becomes acidic and infertile as plant nutrients are washed out by rain (leaching)
What is loam-based soil ?
Ideal medium- well-drained, fertile, and easily cultivated because its a mixture of clay, silt & sand
Importance of organic matter-
Reservoir of nutrients which are released into soil & absorbed by plants
Improves water holding capacity- helps prevent waterlogging & dehydration
binds/ clumps soil into aggregates that improve soil structure allowing it to take up and hold water better
Prevents soil erosion- stabilizes the soil & promotes stronger plant growth
Increased water infiltration- prevents soil from drying out & wind erosion
Define Subsistence farming :
Self-sufficiency farming in which farmers concentrate on growing or rearing enough food to feed themselves and their families with perhaps a little surplus generated occasionally (eg. Asia, Africa)
Define Commercial farming :
farming for a profit- growing crops or rearing animals to sell at market (e.g. MEDCS)
Define Arable farming
production of food, fodder and industrial crops
Define Slash and burn method
Type of subsistance
Clear felling & burning forests to create fields for crops & graze cattle- ash provides a fertility boost
Define Pastoral farming
Rearing animals for meat/ animal products (eg wool)
Define Intensive farming
Large investments of capital & technology to achieve high yields or output
Define Extensive farming
Not using external methods- letting it grow naturally
Define Irrigation
Artifically diverting water to farming areas to grow crops and sustain livestock
Where do the components of soil come from?
- Inorganic material particles- weathering & erosion of rocks
- Organic matter- from plants, animals, microorganisms and humus
- Water- precipitation (rain/snow) that drains into the soil
- Air- carbon dioxide > oxygen
Define humus
Decaying reamins of plants, animals and microorganisms
Most important minerals required by soil & why?
- Nitrogen- combines with glucose to form amino acids- create proteins for cell growth
- Phosphorous- required for respiration and growth & imp for DNA and cell membranes
- Potassium- for enzymes required for photosynthesis and respiration to function
- Magnesium- manufacturing chlorophyll needed for photosynthesis
Natural sources of plant nutrients
- Mineral ions (Nitratres, phosphates etc.)
- Organic Material
Define organic material
Remains of a plant or animal that was once alive and which has returned to the soil and been decomposed into humus by bacterial microorganisms
Define permeability
Ease with which water is able to infiltrate or move through the soil
What soil’s pH mean:
Below 7 (acidic)- nutrients won’t dissolve easily & won’t be able to go up the roots
6-7.5 (neutral)- nutrients will dissolve perfectly
Above 7 (alkaline)- nutrients won’t dissolve easily & won’t be able to go up the roots
Why would soil become more acidic over time?
- Rainfall weathers, washes and leaches certain minerals
- Decomposition of organic matter naturally adds acid
- Acid rain
- Use of chemical- based fertilisers on farms
Define agriculture
Agriculture or farming is the cultivation of the soil for the growing of crops and the rearing of animals
Intensive farming techniques to increase agricultural yield
- Rotation
- Fertilisers
- Irrigation
- Controlling pests and diseases
- Mechanisation
- Selective breeding
- Genetic modification/engineering
- Controlling growing environments
Explain crop rotation
Regularly changing the crop that grows in a particular place on a farm according to an agreed sequence
Growing the same crop in the same field continuously depletes the soil of the range of nutrients a plant requires to yield well
Therefore, with this method that crop will be replaced with a crop that draws other nutrients or returns the depleted nutrient through ‘nitrogen fixing’
Explain nitrogen fixing
(Symbiotic relationship)
Plants such as clovers, peas, beans are ‘legume’ plants that contain a special nodule that holds bacteria which feeds by extracting nitrogen from the atmosphere to produce nitrate chemical compounds
Benefits of crop rotation
- Maintains soil fertility
- Improves crop yields
- Controls bacteria, fungus, parasite build-up
Define fertiliser
Any natural or synthetic substance that is added to soils to supply one or more nutrients removed by growing crops
Explain decompostition
The nutrient ions decompose into the soil as plants die by bacteria
They break down organic molecules and release nutrients back into the soil
Benefits of fertilisers
- Replace lost nutrients
- Maintain the productivity of the land through constantly providing optimum conditions for plant growth
How can you replace lost soil fertility sustainably?
- Rotation
- Nitrogen fixing legumes
- Composted waste produced
- Natural animal manures
Disadvantages of using fertilizers
- Eutrophication
- Soil acidification
- Contributes to greenhouse gas emissions (using nitrogen fertilizers release nitrous oxide)
Define eutrophication
It occurs when fertilisers are washed off the land by rainwater into rivers and lakes
High concentration of nitrates and phosphates build up which causes rapid algae growth, ‘blooms’
These cover the water surface which prevents light and oxygen from reaching the aquatic life
Once dead, bacteria breaks it down which leaves the waterbody devoid of life
Types of irrigation
- Surface irrigation
- Localised irrigation
- Sprinkler irrigation
- Sub/seepage irrigation
- In-ground irrigation
Define surface irrigation
Covering/ flooding entire cultivated area with water
Define localised irrigation
Small drops to the roots through a network of narrow rubber pipes
Define sprinkler irrigation
Imitates rainfall
Water piped then sprayed
Define sub/seepage irrigation
Provides roots with water from beneath the soil
Define in-ground irrigation
Entire irrigation system burried underground
Types of pesticides
- Fungicides
- Herbicides
- Insecticides
Difference between the 3 pesticides
Fungicides kill fungi that attack plants
Herbicides are used against weeds which absorb toxins through their roots and leaves
Insecticides kill insects that attack crop plants
Disadvantages of pesticides
- They destroy the target and also harmless, potentially useful non-pest species
- This destroys the food chain - Bio accumulation
- Populations of apex predators especially will decline - Overuse will lead to insects & weeds becoming resistant or immune
Define bioaccumalation
The gradual build-up of pesticide-spread toxins in organisms in increasing amounts up the food chain
Alternatives to synthentic chemical based methods of controlling pests
- Encouraging their natural predators to attack them
- Rotation won’t allow them to build up
- Mixed cultures > Monocultures making it harder for pests to locate their main crop
- Labour intensive methods (picking insects by hand)
- Naturally made pesticides- made from dried flowers
Benefits of mechanisation
- Cheaper- individually treating plants according to what they need
- Faster/ more efficient- no human error/holidays
- Enabled land that was previously impossible to farm to be brought into cultivation
Ecxplain selective breeding
Increases yields by only breeding from the best animals/ plants.
Pastoral- breeding from the most efficient animal, genes passed in offspring, farmer left with many efficient animals
Arable- cross breed a highly efficient plant with a highly resistant to disease plant to create the best plant
Explain genetic modification
Artifically changing the genetic structure of the cells of farm crops or animals by swapping genes within and across species to improve yields
Selective breeding in a laboratory
Benefits of a controlled growing environment
- Farmer has complete control
- Farmer’s costs reduced and profits increased due to shortened growing season
- Extra CO2 pumped–> more photosynthesis
- Less pesticides used (hydroponics)
Impact of agriculture
- Overproduction and waste
- Cash crops replacing food crops in LEDCS
Reasons for overproduction in MEDCs
- Farmers recieve a minimum wage type subsidy for producing food. If they produce excess the government will buy the surplus
- Market is saturated already
- Low quality, pests, disease, weather– > can’t be harvested
Reasons for wastage by consumers in MEDCs
- Supermarket conditions ‘buy 1 get 1 free’
- Poor packaging and consumer knowledge
(labels confusion & not sure how to store)
Benefits for LEDCs producing cash crops they can export to MEDCs for profits
- Have cash to buy food locally
- Employ relatives
- Pay for family expenses
Disadvantages of planting cash crops from LEDCS
- Farmers don’t get to set their prices
- Very vulnerable to change in demand
- If cash income drops, farmers will face malnutrition or be forced to move
- Small land not viable for cash crops, they’ll have to sell to larger estates
- Cash crops require more water (deplete water supplies) & nutrients in soil won’t be replenished
Causes of soil erosion
- Overcultivation
- Overgrazing
Explain overcultivation
Continous and excessive use of farmland for crops to a point where soils are depleted of nutrients and the soil structure is severely broken down by a lack of organic matter
Explain overgrazing
It degrades the land by stripping away it’s vegetation cover as a result of the density of livestock being greater than the carrying capacity of the soil
What is land degradation
Removing the protective cover of vegetation and its roots and allowing the soil structure to disintegrate to a point where the land no longer has an economic or ecological value
Impacts of soil erosion
- Removes essential nutrients from the land
- Desertification–> Displacement of people
- Habitat loss
- Silting up of rivers
- Sedimentation which damages the barrier reef
Define leaching
Soaking away of soluble nutrients because, as a result of overcultivation or grazing, there are too few plant roots in the soil to absorb the nutrients and lock them away in plant tissue
How can you manage soil erosion?
- Conserve/ Plant vegetation cover- root systems anchor the soil
Eg. Wind breaks: Lines of trees planted to face the prevailing wind and filter out 50-60% of its strength
- Cropping systems and ploughing techniques
Intercropping rather than monocropping has more fertile soil
Contour ploughing allows rainwater more time to soak into the soil and prevent rapid run-off
Define intercropping
Growing 2 or more crops in the same field or area
Cropping systems
Intercropping (E.g Mixed cropping)
Monocropping
Row/Strip cropping
Define sustainable agriculture
Farming that seeks to balance profitable yields of crops and livestock with protecting and conserving the ecosystems upon which all life depends, ensuring the fair and ethical working conditions and remuneration of workers and safeguarding the health and welfare of consumers and all farmed species
How can you farm sustainably?
- Pay workers minimum wage
- Crop rotation (soil fertility maintained)
- Rotational grazing
- Avoid synthetic fertilizers
How do you protect water in the environment?
- Targeted drip irrigation systems
- Low pressure sprinkler systems
- Harvest rainwater run-off from roofs
- Technology can be used to detect how much water is actually needed
