Agriculture Flashcards
What are the key principles of agriculture?
- selection of species
- control of abiotic and biotic environmental factors to control production
- manipulation of the food species to improve productivity
How are species selected for agriculture?
- market demand and access
- whether environmental conditions are within the range of tolerance of the food species
- whether environmental conditions or the species’ adaptations can be controlled to improve productivity
What is the importance of suitable temperatures?
- length of the thermal growing season = must be warm enough for growth
- frost-free period = some crops are damaged by frost
- impact on evaporation = higher temperatures increase the rate of evapotranspiration which increases crop water requirements
- biochemical reactions = rate of biochemical reactions, are increased by higher temperatures
- thermoregulation = mammals and birds use food to maintain a constant internal body temperature, keeping them warm reduces heat lost and increases amount of food energy into growth
How can you control temperature?
- low-lying areas = more frost as cold dense air collects
- south-facing fields = more solar insulation
- greenhouses can achieve higher temperatures
- burning gas, oil or coal in orchards to prevent frost
- transparent cloth over fields to retain warm air close to ground and protect crop seedling
- livestock in shelter
Why is light important in agriculture?
- light intensity affects the rate of photosynthesis, brighter light producing more rapid photosynthesis
- photoperiodism affects the growth and development of crops
- day length can affect the reproductive function of some livestock species:
- long day length increases milk production
- poultry grow best with short days while egg production best in long days
- some livestock mate as days get shorter in autumn
How can light be controlled in agriculture?
- artificial lighting can be used to extend the growing season
- artificial production of autumn lighting conditions in spring will produce another mating season for sheep
Why is water important in agriculture?
- physiological functions = solvent in cells
- nutrient absorption = nitrogen, potassium, phosphorus
- to transport material such as glucose, oxygen and minerals
- transpiration
- gas exchange
How can water supply affect crops?
Amount = affected by precipitation rates and soil properties such as permeability and water retention
Reliability = difficult to plan activities of it is unknown how much water will be available
Quality = substances dissolved in irrigation water can cause problems, especially if ground water or polluted river water is used, high salt can cause salivation = osmotic dehydration, heavy metals may bioaccumulate
What problems are caused by water logged soils?
- higher risk of fungal diseases
- soils become anaerobic and create ideal conditions for denitrifying bacteria, reducing soil fertility as nitrates are lost from the soil more rapidly and replaced more slowly
What methods are used to reduce soil water levels
- excavation of drainage ditches or installing drainage pipes
- deep ploughing
- avoidance of soil compaction by machinery or livestock
- provision of conditions to encourage worms
What problems are caused by water shortages?
Crops:
- severe water shortages will kill plants as cell dehydration inhibits cellular biochemical reactions
- plants lose water in transpiration, reduced when it is to dry
Livestock:
- increase trampling damage as animals have to walk long distances to reach water
What methods are used to increase water availability?
- crop irrigation
- soil mulching to reduce evaporation losses
- provision of suitable conditions for worms
- reducing soil compaction
- adding soil organic matter
What is soil fertility?
A measure of the ability of the soil to support plant growth it is the combination of soil properties such as the availability do nutrients and water aeration, texture and structure.
Why are nutrients needed for soil to be fertile?
- plants need a range of nutrients for growth and good health
- nutrients must be added to replace the nutrients removed when the crop is harvested
How can nutrients get made available by natural processes in the soil?
- legumes have symbiotic nitrogen-fixing bacteria in root nodules e.g. Rhizobium
- some free-living soil bacteria also fix nitrogen e.g. Azotobacter
- crop rotation gives time for weathering to release more nutrients and even out the demands for particular nutrients by different crops
What are the advantages and disadvantages of organic fertilisers?
ADV:
- many are waste products
- locally available
- increase soil humus content
- increase soil biota
DIS:
- nutrient compositions cannot be controlled
- nutrients are released slowly
- bulky with a high water content = expensive transport
- usually cannot be added to a growing group
What are the advantages and disadvantages of inorganic fertilisers?
ADV:
- nutrient composition can be controlled
- nutrients are rapidly released
DIS:
- some require large amounts of energy during manufacture
- do not add organic matter to the soil
- toxic to worms
- high solubility and may be leached
What nutrient application methods are there?
- cultural methods using natural processes such as bacterial fixation and weathering release nutrients in the soil
- crop rotation cycle that includes livestock will add manure to the soil
- mechanical application is normally used to spread organic and inorganic fertilisers
What are hydroponics?
Involves the growth of crops in a nutrient solution rather than a solid growth medium, usually carried out in greenhouses as part of an intensive system.
What are the advantages and disadvantages of hydroponics?
ADV:
- nutrient supply is optimal
- all roots are in contact with nutrient medium
- no soil to hold pathogens
- no weeds
- harvested crop still has roots so it stays fresh for longer
- harvested crop is attractive for customers
DIS:
- intensive production involves high inputs of nutrient and energy
- a high level of technical knowledge is needed
What are some farming practices that increase soil compaction?
- weight of machinery or livestock
- less organic matter content = less worms
- natural communities have deep-rooted plants, most crops have shallow roots
- ploughing can kill organisms
How is aeration controlled?
- ploughing turns over and aerates surface soil layers but not deeper layers
- adding organic matter attracts soil biota
- low tillage methods prevent the disturbance to soil and the killing of soil organisms
- removing live stock from fields when it is very wet
Why is soil salinity important to agriculture?
- dissolved salt in soils are essential for plant growth
- excessive salinity can kill plants by osmotic dehydration of their roots
- irrigating with high salt content ground water needs to be avoided
- extra water can be used to wash the salts out of the soil
Why is soil pH important in agriculture?
- all species have range of tolerance for pH
- a high pH can inhibit nutrient solubility
- low pH can increase the leaching of nutrients and inhibit nutrient uptake
- soil pH can be increased by adding crushed lime
- soil pH can be reduced by spreading powdered sulphur
Why is carbon dioxide concentration important to agriculture?
- can be a limiting factor on the rate of photosynthesis
- can be kept in a greenhouse
How is topography important to agriculture?
Aspect: undulations, such as valleys, produce some areas which are more exposed to sunlight and tend to be warmer
Frost pockets: cold dense air may collect in low-lying areas, making crop frost damage more likely
Runoff rate: steeper gradients make soil erosion by by surface runoff more likely
Use of machinery: it may be difficult to operate large machinery on land that undulates a lot or where gradients are very steep
How is topography controlled?
- terracing can reduce the gradient of a slope
- area that are nearly flat may be levelled by machinery so that water drains slowly
Why is relief important to agriculture?
Crops:
- temperatures are often colder at higher altitudes, the low atmospheric pressure increases the evaporation rate
Livestock:
- some species are adapted to high altitudes such as goats, sheep, llamas
What problems does high wind velocity cause and how can it be controlled?
- increased soil erosion, especially in dry areas
- increased evaporation rates and the drying of soils
- crop damage
- can be controlled by hedgerows and windbreaks
What are pests and what do they do?
Organisms that reduce agricultural productivity or the quality of the product:
- be predators that eat the crop or livestock
- compete for resources such as water or nutrients
- be pathogens
- carry pathogens
- reduce marketability
What is the difference between endemic and epidemic pests?
- epidemic pests species are not normally present but there may be outbreaks
- endemic pests are always present
Whats the difference between introduced and indigenous pests?
- indigenous pests are native to the area where they are found
- introduced pests come from other areas
What is cultural pest control?
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What is cultural pest control?
Involves non-pesticide methods where crops or livestock are cultivated in a way that reduces the risk of pest damage, often by using natural ecosystem services.
What is crop rotation?
- different crops often have their own unique pest species, if different crops are grown each year then the pest species dies out and will have to recolonise each time so their populations with be smaller.
What are the four types of companion crop?
- Nutrient supply = legumes can be intercropped among other crops to increase nitrate availability in the soil
- Barrier crops = the smell of onions can mask the smell of carrots and reduce damage caused by carrot flies
- Pest attraction to protect the other plant = nasturtiums attract blackfly pests that could damage bean crops
- Support of pollinators = flowering plants that support bees which are important in pollinating crops
What are predator habitats?
- populations of natural pest predators can be increase by providing suitable habitat
What is biological control?
- predator or pathogen species may be introduced to control pests, especially important if the pest is a non-indigenous spefies that has been introduced and has no indigenous predators.
- they should be specialist feeders that will eat the pest species
- they have a wider diet then they may eat beneficial and other non-target species
What are sterile male techniques?
- female insects only mate once and store sperm for all future eggs, if a female mates with a sterile male then she will never produce any offspring
- achieved by exposing them to gamma radiation
- herd immunity
What are pheromone traps?
- release an artificial scent that attracts pests, they can be used in two ways:
- to show the pest is present so pesticides can be used
- to kill all the pest individuals or enough of one gender that they can’t reproduce
What is genetic resistance to disease?
- selective breeding may enhance the resistance of a variety to pests or disease
What is GM crops and pest control?
The DNA of a crop can be modified to control pests more effectively by reducing susceptibility to pests
How does toxicity influence a pesticides effectiveness and environmental impacts?
- high toxicity require the use of smaller volumes, most pesticides act by inhibiting enzyme action
How does specificity influence a pesticides effectiveness and environmental impacts?
- a measure of the range of taxa affected by the pesticide
- more specific pesticides are less likely to harm non-target species
How does persistence influence a pesticides effectiveness and environmental impacts?
- persistent pesticides are chemically more stable and degrade slowly
- reducing the frequency of reapplication but can increase the likelihood of a pesticide dispersing more widely in the environment and may extent the time that it may harm non-target species
How does solubility in water/lipids influence a pesticides effectiveness and environmental impacts?
- water soluble are more likely to be washed off a crop, requiring reapplication and are more likely to be carried into water sources
- lipid soluble may be absorbed and stored with in the crop, potentially entering the human food chain
How does mode of action influence a pesticides effectiveness and environmental impacts?
Contact action: kill plants by damaging tissues they are sprayed onto, kill insects that are sprayed directly or some in contact with the pesticide that was sprayed on the crop being protected, unsprayed surfaces are not protected and could be washed off in the rain
Systemic action: absorbed by the crop and translocated throughout the plant, this protects all of the plant and will also protect new growth, cannot be washed off but could be eaten by humans
How do antibiotics influence a pesticides effectiveness and environmental impacts?
Chemicals that kill microbes such as pathogenic bacteria, they are used to:
- treat infections
- prevent infection
- promote growth: increase Gross Growth Efficiency of livestock
- large scale use of antibiotics as growth promoters increases risk of producing antibiotic resistant bacteria, these can be passed to humans
How does hormone pesticides influence a pesticides effectiveness and environmental impacts?
- kill pests through their biochemical action, they kill by increasing or staring natural processes in a way that is harmful to the pest
- some hormones cause insects to metamorphose into adults before they are large enough function properly so they die, other prevent chitin skeleton forming
- have low persistence and are more specific than most pesticides
What is extensive agriculture?
It aims to maximise the total yield by spreading the available inputs of a large area of available land.
What is intensive agriculture?
It is practised where large inputs are available by there may be a shortage of land, yields per unit area may be very high but your extra yield per unit input may not be
What is an energy subsidy?
Any input that aids productivity but requires the use of energy in an agricultural system
What are some major agricultural energy subsides?
- manufacture of nitrate fertilisers
- manufacture of pesticides
- pumping of irrigation water
- fuel for machinery for ploughing, spraying or harvesting
- energy from the manufacture of machinery and equipment
- heat for drying harvested grain
- processing food for customers
- transport of food to customers
