Abiotic Factors And Their Control Flashcards
How does control of abiotic factors affect an environment?
Each species has its own range of tolerance part of this range will be optimum for survival and growth maintaining these conditions will maximise productivity
What is the importance of suitable temperature conditions for length of the thermal growing season?
It is not necessary for temperatures to be warm enough for survival it must be warm enough for growth,
What is an example of it being warm enough for growth?
Grass can survive very low temperatures but does not grow at temperatures below 5*c
What is the importance of suitable temperature conditions for frost free period?
Some crops are damaged by frost
What plant can be damaged by frost?
Maize
What part of plants is affected by frost?
The blossom of many fruit crops is damaged by frost
What is the importance of suitable temperature conditions for its impact on evaporation?
Higher temperatures increase the rate of evapotranspiration which increases crop water requirements
What is the importance of suitable temperature conditions for biochemical cycles?
The rate of biochemical reactions (photosynthesis and plant growth) are generally increased by higher temperatures
What is an example of a biochemical cycle?
Photosynthesis
What is the importance of suitable temperature conditions for thermoregulation?
Mammals and birds use food energy to maintain a constant internal body temperature
Keeping animals warm reduces heat losses and increases the amount of food energy put into growth
How can low lying areas affect the temperature?
Low lying areas such as valley bottoms are more likely to have frosts as cold dense air collects there
How can south facing-slopes affect the temperature?
South facing slopes in the northern hemisphere (north facing slopes in Southern Hemisphere) tend to be warmer
What intensive heating methods can be used to grow valuable crops in cooler areas?
Greenhouses achieve higher temperatures form solar heating
Greenhouses may be heated in cold weather by burning fuel ( Gas or paraffin)
Greenhouses overheating can be prevented by ventilation
What happens to orchards in colder temperatures?
Frost in orchards when flowering can destroy the flower and prevent any crop from being produced
How can the frost affect on flowering orchards be prevented?
Burning gas, oil or candles
Dispersing cold air with large fans
How can crop seedlings be protected?
Transparent woven plastic cloth over field helps retain warm air close to the ground
How can livestock be kept warm?
By providing shelter or buildings that may be heated
What can be done to buildings to prevent overheating?
May need to ventilated
Why is light important for photosynthesis?
Intensity of light affects the rate of photosynthesis, brighter light producing more rapid photosynthesis
What is photoperiodism?
Day length
Why is day length important? (agriculture)
Some plants require longer periods of light each day for flowering
Day length can affect the reproductive function of livestock
What is an example of how period of light during the day affects the flowering of plants?
Oats require longer periods of light each day
Maize requires shorter days
How can day length affect livestock?
Long day length increases milk production
Poultry grow best with short days while egg production is best when day are long
Sheep mate when days are getting shorter in the autumn (lambs in spring)
How can light be controlled?
Artificial lighting can be used to extend the growing season in greenhouses
What plant is grown using artificial lighting?
Salad crops
Why is autumn lighting simulated?
In spring it will produce another mating season for sheep (lambing in autumn)
What are the physiological functions of water?
Water is the general physiological solvent in all living cells
Why is water important for nutrient absorption?
Nutrients are absorbed from the soil as ions dissolved in water
What are some examples of nutrients absorbed as ions?
Nitrogen is absorbed as nitrate ions
Phosphorus is absorbed as phosphate ions
Potassium is absorbed as potassium ions
Why is cell turgidity important?
Cell water produces cell turgidity which provides support (especially in seedlings)
Why is water important for transportation?
Used to transport materials such as glucose, oxygen and mineral nutrients
Why is water important for transpiration?
Needed to replace the water lost during transpiration
Why is water important for gaseous exchange?
Stomata are the pores where carbon dissolve and is absorbed (photosynthesis) water lost by evaporation in this process from the stomata
Why do stomata on a plant close?
To prevent dehydration and death
What is the amount of water in fields affected by?
The amount of water is affected by precipitation rates and soil properties such as permeability and water retention
What is the ‘hydrological growing season’?
The time during the year that there is sufficient water to sustain growth
How does reliability of water supply affect crops?
Difficult for farmers to plan activities if they do not know how much water will be available especially in areas with unreliable seasonal rainfall or where the is no other alternative for irrigation
How does quality of water supply affect crops?
Substances dissolved in irrigation water can cause problems especially if groundwater or polluted river water is used
What can a high salt content in water cause?
Salinisation leading to osmotic dehydration of crops
How can water polluted by heavy metals cause problems for crops?
May bioaccumulate in crops and be a threat to the health of the people who eat the harvested crop
What are the problems form water logged soil?
Higher risk of fungal disease
Soils become anaerobic and creat ideal conditions for denitrifying bacteria but not nitrifying bacteria reducing soil fertility as nitrates lost is fast and regain is slow
What methods are used to reduce soil water levels?
Excavation of drainage ditches or installation of drainage pipes
Deep ploughing
Avoidance of soil compaction by machinery or livestock
Provision of conditions to encourage worms
What are the problems of water shortages on crops?
Plants lose water by transpiration during dry weather but loss reduced by closing of stomata
This also stops absorption of CO2 so photosynthesis stops as does growth
What can a moderate water shortage do to crops?
Reduces crop productivity
What can a severe water shortage do to plants?
Will kill plants as cell dehydration inhibits cellular biochemical cycles
How are livestock affected by water shortage?
Livestock is semi-arid areas may die if there is a water shortages
How can water shortages increase livestock trampling?
As animals will regularly walk longer distances to reach water
Increase the rick of erosion and desertification
What methods can increase water availability?
Crop irrigation
Soil mulching to reduce evaporative losses from soil surface
Provision of suitable conditions for worms to increase infiltration and reduce runoff losses
Reducing soil compaction by machinery and livestock to increase infiltration and reduce runoff losses
Adding soil organic matter to increase water retention
What is soil fertility?
The ability of the soil to support plant growth
What soil properties encompass soil fertility?
Availability of nutrients and water
Aeration
Texture
Structure
What are nutrients that are needed in large amounts called?
Macro nutrients
What are nutrients that are needed in smaller amounts called?
Micronutrients
When must nutrients be added to the soil?
To replace the nutrients removed when the crop is harvested or if the soil is naturally deficient in that nutrient
What are the primary macronutrients?
Nitrogen
phosphors
potassium
What are the secondary macronutrients?
Calcium
Magnesium
Sulphur
What are the most common micronutrients?
Iron
Zinc
Copper
What forms are the primary macronutrients absorbed in?
Nitrate ions - nitrogen
Phosphate- phosphorus
Potassium ions - potassium
`what forms are the secondary macronutrients absorbed in?
Calcium ions - calcium
Magnesium ions - magnesium
Sulphate ions - sulphur
What forms are the micronutrients absorbed in?
Iron ions - iron
Zn - zinc
Cu- copper
What are the functions of the primary macronutrients?
Nitrogen- protein growth
Phosphorus- root growth + ATP manufacture
Potassium- ion transport and seed development
What are the functions of the secondary micronutrients?
Calcium - cell walls
Magnesium- chlorophyll synthesis
Sulphur - protein synthesis
What are the functions of the micronutrients?
Iron- chlorophyll manufacture
Zinc- enzyme activation
Copper - enzyme activation
Are the primary macronutrients commonly applied to fields as fertilisers?
Yes for all three
Are the secondary macronutrients and micronutrients comply used as fertilisers on fields?
If the soil is nutrient deficient or in intensive systems such as hydroponics
What natural processes can make nutrients available in the soil?
Legumes
Azotobacter free living soil- bacteria
Crop rotation
What do legumes have a symbiotic relationship with?
Nitrogen fixing bacteria in the root nodules (Rhizobium)
How does crop rotation add nutrients to the soil?
Gives time for weathering to release more nutrients
Even out the demands of different crops
What are organic fertilisers?
Plant and animal matter that release nutrients as they decompose
What are some examples of organic fertilisers?
Faecal material: manure/ sewage sludge
Animal food production wastes: bone meal/ fish meal/ dried blood
Plant food production wastes: crop harvest wastes/ composted plant waste
What are the advantages of organic fertilisers?
Many waste products are locally sourced
Increase soil humus content
Increase soil biota populations
What are the disadvantages of organic fertilisers?
Nutrient composition can’t be controlled
Nutrients released slowly as material decomposes (long term cultivation plan)
Bulky and high water content making it expensive to transport
Usually can’t be added to growing crop
What are the advantages of inorganic fertilisers?
Nutrient composition can be controlled to meet specific crop requirements
Nutrients are released rapidly
What are the disadvantages of inorganic fertilisers?
Some need large amounts of energy during manufacturing
Do not add organic matter (humus and biota may decline)
Some are toxic to worms
Some have high solubility so may be leached after application
Raw materials for manufacturing may be limited
What are the cultural methods of nutrient application?
Bacterial fixation and weathering release the nutrients in the soil
Crop rotation cycle that involves livestock to add manure
What is mechanical application?
The use of fertiliser spreader/ machinery
What is hydroponics?
The growth of crops in a nutrient solution rather than a solid growth medium
Where is hydroponics usually carried out?
In a greenhouse as part of an intensive system where productivity is maximised
What are the advantages of hydroponics?
Nutrient supply is optimal so this doesn’t limit growth
All roots in contact with nutrient medium so roots are small and growth focused on crop
No soil to hold pathogens
No weeds
Harvested crop still has roots so stays fresh for longer
Attractive for consumers as no soil
What are the disadvantages of hydroponics?
Intensive process involves heavy input of nutrients and energy
A high level of technical knowledge is needed
what type of soil has increased aeration?
uncompacted soil with larger spaces between soil particles
why is aeration important? (Soil)
many soil processes are aerobic
root respiration
nitrogen fixation
decomposition
What naturally causes soil particles to become compacted?
The force of gravity
How is gravity soil compaction counteracted?
The tunnelling action of detrivores
What soil biota have tunnelling actions?
Worms
Roots (larger plants , create drainage channels when they die)
What farming practices increase soil compaction?
The weight of farm machinery or livestock trampling
Farming methods often reduce soil organic matter therefore worm populations
Natural communities have deep rooted plants ,forests, but crops commonly have short roots
Ploughing can kill soil organisms by moving them to depths they cannot survive
How can ploughing control aeration?
Ploughing runs over and aerates surface soil layers but not deeper layers
How can organic matter increase aeration?
Provides food for soil biota that increase aeration
How can low tillage methods control aeration?
Prevent soil disturbances and the killing of soil organisms during ploughing
How can the removal of livestock control aeration?
Remove livestock when the field is wet reducing the compaction caused by trampling
Why is soil salinity important?
Dissolved salts in the soil water are essential for plant growth as they include soil nutrients
What is the problem if soil salinity is too high?
Can kill plants by osmotic dehydration of their roots
What is the main method to to control salinity?
Avoid farming methods that increase salinity (irrigating groundwater that has a high salt content)
How does the salt concentration in the soil increase?
As the salts are left in the soil when the water evaporates from the soil
What can be done to reduce soil salinity?
Extra water can be used to wash the salts of the soil but this greatly increases consumption and can increase the salinity of local water channels
What is the common pH range?
Between 5 and 7
What can a high pH inhibit?
Nutrient solubility
What can a low pH cause?
Increased leaching of nutrients and inhibit nutrient uptake
How can soil pH be increased?
Adding crushed lime (calcium carbonate or hydroxide)
How can soil pH be reduced?
Spreading powdered sulphur
What can be a limiting factor for photosynthesis rate?
Carbon dioxide concentration
Why is it not practical to increase carbon dioxide concentrations in the field?
As it will simply diffuse away as there is nothing to keep the Carbon dioxide contained
Where is it practical to increase carbon dioxide concentrations?
In greenhouses by burning fossil fuels (gas or paraffin)
How can cost of increasing Carbon dioxide contractions be justified?
The high market value of greenhouse crops
How can topography affect agriculture?
The undulations of the land surface can affect its suitability for particular crops and the methods that are used
How can topography aspect affect agriculture?
Undulations such as valleys produce some areas which are more exposed to sunlight and tend to be warmer
What are frost pockets?
Cold dense air may collect in low lying areas, making crop frost damage more likely
How are topography and runoff rates connected?
Steeper gradients make soil erosion by surface runoff more likely
Gentle or flat gradients make saturation more likely
How can the use of machinery be affected by topography?
It may be difficult to operate large machinery on land that undulates a lot or where gradients are very steep
Can topography be controlled?
Not practical to alter the topography of large areas of land but it may be possible in some areas
How can topography be controlled?
Terracing can change a steep field into many flat fields
Why is terracing done?
To retain irrigation water and reduce soil erosion
How can topography of nearly flat areas be changed?
Areas that are nearly flat may be levelled by machinery so that water drains slowly reducing irrigation needs
How can relief affect agriculture?
The altitude of an area controls other factors that affect the choice of species for cultivation
How can relief affect crops?
Temperatures are often colder at higher altitudes
Low atmospheric pressure increase he evaporation rates
Is it possible to control relief?
No
How can relief affect livestock?
Some species are adapted to high altitudes they can survive lower temperatures and low atmospheric pressures
What animals can survive at high altitudes?
Goats
Sheep
Llamas
