Topic 11: Abiotic Factors And Their Control Flashcards
Why is it important to control abiotic factors in agriculture?
Every species has its own range of tolerance for every abiotic factor
By maintaining conditions in optimum range results in optimum productivity
Abiotic factors controlled in agriculture
Temperature
Light
Water
Soil fertility
Aeration
Soil salinity
Soil ph
CO2
Topography
Wind
Importance of suitable temperatures
Length of thermal growing season
Frost-free period
Impact on evaporation
Biochemical reactions
Thermoregulation
Why is the length of the thermal growing season important?
Needs to be warm enough for growth, not just survival
Increased temp, increases photosynthesis, plants lose water faster
Why is a frost-free period important?
Some crops are damaged by frost
E.g. maize
They are particularly damaging to flowering plants
How does global worming affect the frost-free period?
Global warming means earlier flowering seasons
So plants are more vulnerable/exposed to frost
Impact of temperature on evaporation?
Higher temps, higher evapotranspiration
This increases the crops water requirements
Impact of temperature on biochemical reactions
Rate is increased by temperature
Including those involved in photosynthesis and plant growth
Importance of thermoregulation
Mammals/bords use food energy to maintain constant internal body temperature
If it is cold, more energy than usual is used for temperature instead of for growth
How can temperature be controlled?
The selection of fields can affect temperature- low lying areas are more likely to experience frost
Or southern facing slopes in the northern hemisphere will be warmer
Intensive methods e.g. greenhouses
Transparent plastic cloths can be placed over fields to help retain warm air close to the ground
Iivestock kept in shelters or heated buildings
How is light important in agriculture/
For photosynthesis
explain the effects of variation in light intensity
Photoperiodism (daylength)- some plants require longer daylight periods for flowering
Daylength can also affect reproductive functions of livestock species
How can light be controlled?
Artificial light used to extend growing season
The artificial production of autumn lighting conditions in spring-produce another mating season and lambing season in the autumn
Importance of water
Physiological solvent
Nutrient absorption
Cell turgidity
To transport materials
To replace water lost in transpiration
Gaseous exchange-stomata
Name a crop with a high water requirement
Most rice varieties
Give a crop with a low water requirement
Wheat
In what ways can water supply affect crops?
Amount available
Reliability
Quality
How can the amount of water affect crops?
Plants are adapted to the amount available
They might have complex rot systems to increase SA in contact with water that contains nutrients
Might have longer roots in clay soil to reach water under clay
How can the reliability of water affect crops?
Difficult for farmers to plan activities if they dont know about water availability
Particular issue in areas with unreliable seasonal rainfall
In reliable climates make it more difficult expensive to farm
How can the quality of water supply affect crops?
If substances are dissolved in irrigation water it can be an issue
High salt content can cause salinisation which leads to osmotic dehydration
What problems are caused by waterlogged soils?
Higher risk of fungal or infectious diseases
Soils become anaerobic-better for denitrifying bacteria, which reduces soil fertility as nitrates are lost
What methods can be 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-aeration
Problems for crops caused by water shortages
Plants close stomata to prevent water loss, which prevents co2 absorption nd photosynthesis
Reduces crop productivity
Lack of water reduces cell turgidity and means there is no solvent for reactions
Problems for livestock caused by water shortages
Increased trampling damage if have to walk longer distances for water
Increases risks of erosion and desertification
Livestock have to go on get distances-reduces body mass, kills more plants
Methods to increase water availability
Crop irrigation
Soil mulching
Suitable conditions for worms
Reduce soil compaction
Add organic matter
When must nutrients be added to soil?
When nutrients are removed in crop harvest or lost in natural processes
If the soil is deficient of that nutrient
Primary macronutrients needed by plants
Nitrogen
Phosphorous
Potassium
Secondary macro nutrients
Calcium magnesium sulfúreo
How can nutrients be applied in agriculture?
Primary macronutrients- fertilisers
Secondary & micronutrients applied if soil if nutrient deficient or in intensive systems e.g. hydroponics
What are organic fertilisers?
Animal or plant material that release nutrients as they decompose
Advantages of organic fertilisers
Many are wast products
Locally available
Increase soil humus content
Increase soil biota
Disadvantages of organic fertilisers
Nutrient composition cant be controlled
Nutrients released slowly
Bulky/high water content-expensive to transport
Usually cant be added to growing crops
Advantages of inorganic fertilisers
Nutrient composition can be controlled to meet specific requirements
Nutrients are released rapidly
Disadvantages of inorganic fertilisers
Require large amounts of energy to manufacture
Don’t add organic matter to soil-humus and biota decline
Toxic to worms
High solubility-leached
What is hydroponics?
Involves the growth of crops in a nutrient solution rather than a solid growth medium
Usually in a greenhouse
Part of intensive system
Productivity is maximised
Advantages of hydroponics
Optimal nutrient supply
All roots in contact with nutrient medium
No soil to hold pathogens
No weeds
No pollutants
Crops fresher for longer
More attractive to customers-no soil on them
Disadvantages of hydroponics
Very expensive
Requires high energy and nutrient inputs
High levels of technical knowledge needed
why is soil aeration needed?
Root respiration,nitrogen fixation,decomposition
How is soil naturally compacted and aerated?
Naturally compacted by gravity
Tunniling of detrivores and roots
How can aeration be controlled?
Ploughing
Adding organic matter
Low tillage methods
Trampling reduced
How can soil salinity be controlled?
Avoiding farming practices that increase salinity e.g. irrigation using ground water with high salt content, because the salt stays in the soil when the water has evaporated
Problems with low soil PH
Can increase leaching and inhibit nutrient uptake
Can mobilise toxic ions
How can soil PH be increased?
Adding crushed lime
How can PH be decreased in the soil?
Spreading powdered sulphur
How can carbon dioxide be controlled?
Increased in greenhouses by burning carbon-based fuel e.g. paraffin
The increased cost may be justified by the higher market value of greenhouse corps
How can wind velocity be controlled?
Windbreakers e.g. hedgerows or Trees
