Biological Resources (A2); Agriculture (Complete) Flashcards
In what ways does farmland cover a large proportion of Earth’s land area?
About 10% being cultivated & further 25% used as permanent pasture
Why is it important that agriculture is sustainable?
Due to a growing human population
Why is agriculture important?
Affects large areas of natural habitats & many important natural processes
What does agriculture involve?
The control of terrestrial ecosystems to divert energy & nutrients into the human food chain
What are the key principles of agriculture?
-Market demand & access
-Whether environmental conditions are within the range of tolerance of the food species
-Whether environmental conditions/species adaptations can be controlled to improve productivity
Why are abiotic factors and their control important for agriculture?
-For every abiotic factor, each species has its own range of tolerance within which it can survive
-Part of that range will be the optimum for survival & growth
-Maintaining conditions within this optimum range will maximise productivity
Abiotic factors & their control- temperature; why are suitable temperatures important for the length of the thermal growing season?
-It’s not just necessary for temperatures to be warm enough for survival, it must be warm enough for growth
-For example, grass can survive very low temperatures but doesn’t grow at temperatures below 5°C
Abiotic factors & their control- temperature; why are suitable temperatures important for frost-free periods?
-Some crops are damaged by frost, eg maize, so it can’t be grown in areas where late frosts are likely
-The blossom of many fruit crops is damaged by frosts
Abiotic factors & their control- temperature; why are suitable temperatures important for their impacts on evaporation?
High temperatures increase the rate of evapotranspiration which increases crop water requirements
Abiotic factors & their control- temperature; why are suitable temperatures important for biochemical reactions?
Rate of biochemical reactions, incl those involved in photosynthesis & plant growth, are generally increased by higher temperatures
Abiotic factors & their control- temperature; why are suitable temperatures important for thermoregulation?
-Mammals & birds use food energy to maintain a constant internal body temperature
-Keeping the animals warm reduces heat losses & increases the amount of food energy put into growth
Abiotic factors & their control- temperature; how do selected field locations affect the temperature?
-Low lying areas eg valley bottoms are more likely to have frosts as cold dense air collects there
-South-facing slopes in northern hemisphere (& north-facing slopes in southern hemisphere) receive more solar insolation, tend to be warmer. Where crop is sufficiently valuable, temps may be raised w/ more intensive methods; greenhouses achieve higher temps from solar heating, may be heated in cold weather by burning fuel eg gas/paraffin & their overheating can be prevented by ventilation
-Frosts in orchards during flowering period can destroy flowers & prevent any crop from being produced. Can be prevented by burning gas, oil, candles in orchards/by dispersing cold air w/ large fans
-Transparent woven plastic cloth over fields helps to retain warm air close to ground & protect crop seedlings
-Livestock can be kept warm by providing shelter/buildings that may be heated. In hot weather, buildings may need to be ventilated to prevent overheating
Abiotic factors & their control- light; what is the importance of light?
-Intensity of light affects rate of photosynthesis; brighter light producing more rapid photosynthesis
-Photoperiodism (daylength) affects growth & development of crops. Some plants require longer periods of light each day for flowering, eg oats, while others require shorter days, eg maize
-Day length can affect reproductive function of some livestock species; long day length increases milk production, poultry grow best w/ short days while egg production is greatest when days are long & some livestock like sheep mate when days are getting shorter in autumn, w/ lambs being born in spring
Abiotic factors & their control- light; how can light be controlled and for what reason?
-Artificial lighting can be used to extend growing season, eg for salad crops in greenhouse
-Artificial production of autumn lighting conditions in spring will produce another mating season for sheep, w/ second lambing season in autumn
Abiotic factors & their control- water; what are the reasons for the importance of water?
-Physiological functions; water= general physiological solvent in all living cells
-Nutrient absorption from soil as ions dissolved in water; nitrogen is absorbed as nitrate ions, phosphorus is absorbed as phosphate ions & potassium is absorbed as potassium ions
-Cell water produces cell turgidity which provides support, esp in seedlings
-Is used to transport materials eg glucose, oxygen & mineral nutrients
-Is needed to replace water that’s lost during transpiration, which causes water to be drawn upwards to leaves, carrying nutrients from roots w/ it
-Gaseous exchange; stomata= pores in leaves where CO² dissolves & is absorbed, so can be used in photosynthesis. Water’s lost during this process by evaporation from cells in stomata. If there’s a shortage of water, stomata close to prevent dehydration + death. Plant may survive, but gaseous exchange & growth will stop
Abiotic factors & their control- water; how can water supply affect crops?
-Some crops have a high water requirement eg most rice varieties must be flooded during early growth
-Some cereal crops have a low water requirement, eg wheat
-Irregular water supplies can cause some crops to expand & split, eg tomatoes
-Humid conditions can increase risk of fungal diseases
Abiotic factors & their control- water; what is the amount of water available for plants affected by?
-Precipitation rates & soil properties like permeability & water retention
-The ‘hydrological growing season’ is the time during the year that there’s sufficient water to sustain growth
Abiotic factors & their control- water; how does the reliability of water affect crops?
-It’s difficult for farmers to plan activities if they don’t know how much water will be available
-This is a particular problem in areas w/ unreliable seasonal rainfall/where there’s no alternative water supplies for irrigation
Abiotic factors & their control- water; how does quality of water affect crops?
-Substances dissolved in irrigation water can cause issues, esp if groundwater/polluted river water is used
-A high salt content can cause salinisation, leading to osmotic dehydration of the crop
-Heavy metals may bioaccumulate in crops & be a threat to health of people who eat harvested crop
Abiotic factors & their control- water; what are the problems caused by waterlogged soils?
-Higher risk of fungal diseases
-Soils become anaerobic & create ideal conditions for denitrifying bacteria, but not nitrifying bacteria—> reduces soil fertility as nitrates are lost from soil more rapidly & replaced more slowly
Abiotic factors & their control- water; what are the methods to reduce soil water levels?
-Excavation of drainage ditches/installation of drainage pipes
-Deep ploughing
-Avoidance of soil compaction by machinery/livestock
-Provision of conditions to encourage worms, eg soil organic matter
Abiotic factors & their control- water; how do water shortages cause problems for crops?
-Plants lose water by transpiration during dry weather but this is reduced by closure of stomata in their leaves
-This also stops absorption of CO² so photosynthesis & growth stop. Even a moderate water shortage reduces crop productivity
-A severe water shortage will kill plants as cell dehydration inhibits cellular biochemical reactions
Abiotic factors & their control- water; how do water shortages cause problems for livestock?
-Livestock in semi-arid areas may die if there’s a water shortage
-Shortages can increase trampling damage if animals have to regularly walk longer distances to reach water; can increase risk of erosion & desertification
Abiotic factors & their control- water; what are the methods to increase water availability?
-Crop irrigation
-Soil mulching to reduce evaporation losses from soil surface
-Provision of suitable conditions for worms to increase infiltration & reduce runoff losses;
-Reducing soil compaction by machinery & livestock to increase infiltration & reduce runoff loses
-Adding soil organic matter to increase water retention
What is soil fertility?
-A measure of the ability of soil to support plant growth
-The combination of soil properties like the availability of nutrients & water, aeration, texture + structure
Abiotic factors & their control- soil fertility; why do plants need a range of good nutrients?
Growth & good health
Abiotic factors & their control- soil fertility; what are macronutrients and micronutrients?
-Nutrients that are needed in large amounts; macronutrients
-Those needed in smaller amounts; micronutrients
Abiotic factors & their control- soil fertility; when do nutrients need to be added to soil?
To replace nutrients removed when crop is harvested, to replace nutrients lost due to natural processes or if soil is naturally deficient in that nutrient
Abiotic factors & their control- soil fertility; how may nutrients be made available by natural processes in the soil?
-Legumes have symbiotic nitrogen-fixing bacteria in root nodules, eg Rhizobium
-Some free-living soil bacteria also fix nitrogen, eg Azotobacter
-Crop rotation gives time for weathering to release more nutrients & to even out demands for particular nutrients by different crops
Abiotic factors & their control- soil fertility; what are organic fertilisers and what do they include?
-Animal & plant material that release nutrients as they decompose
Include;
-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
Abiotic factors & their control- soil fertility; what are the advantages of organic fertilisers?
-Many are waste products & may be locally available
-Increase soil humus content
-Increase soil biota populations
Abiotic factors & their control- soil fertility; what are the disadvantages of organic fertilisers?
-The nutrient composition can’t be controlled
-Nutrients are released slowly as material decomposes, so they must be used as part of a long-term cultivation plan
-Many are bulky w/ high water content so transport is expensive
-Usually can’t be added to a growing crop
Abiotic factors & their control- soil fertility; what are the advantages of inorganic fertilisers?
-Nutrient composition can be controlled to meet specific crop requirements
-Nutrients are released rapidly
Abiotic factors & their control- soil fertility; what are the disadvantages of inorganic fertilisers?
-Some require large amounts of energy during manufacture by chemical industry
-They don’t add organic matter to the soil, so humus levels & soil biota populations may decline
-Some are toxic to worms
-Some have high solubility & may be leached after application
-Raw material supplies for manufacture may be limited, eg phosphate rocks
Abiotic factors & their control- soil fertility; what are methods of nutrient application?
-Cultural methods using natural processes like bacterial fixation & weathering release nutrients in the soil
-A crop rotation cycle that includes livestock will add manure to the soil
-Mechanical application is normally used to spread organic & inorganic fertilisers
Abiotic factors & their control- soil fertility; what does hydroponics involve?
-Growth of crops in a nutrient solution rather than solid growth medium
-It’s usually carried out in greenhouses as part of an intensive system
-Productivity is maximised by controlling limiting factors as much as possible
Abiotic factors & their control- soil fertility; what are the advantages of hydroponic production?
-Nutrient supply is optimal so this isn’t a limiting factor for growth
-Allroots are in contact w/ nutrient medium, so roots are smaller & more growth is directed into harvestable crop
-There’s no soil to hold pathogens
-There are no weeds
-Harvested crop still has roots so stays fresh longer
-Harvested crop is attractive for consumers as it has no soil on it
Abiotic factors & their control- soil fertility; what are the disadvantages of hydroponic production?
-Intensive production involves high inputs of nutrients & energy
-High level of technical knowledge is needed
Abiotic factors & their control- aeration; what increases aeration and why is this important?
-An uncompacted soil has larger spaces betw soil particles; increases aeration
-Force of gravity naturally causes soil particles to become compacted; counteracted by tunnelling action of detritivores eg worms & growth of plant roots, esp of larger plants whose larger roots create drainage channels when they die + decompose
-Important as many important soil processes are aerobic eg root respiration, nitrogen fixation, decomposition
Abiotic factors & their control- aeration; what kind of farming practices increase soil compaction?
-Weight of farm machinery/livestock trampling
-Farming methods often reduce soil organic matter content, therefore worm populations
-Natural communities have deep-rooted plants, eg forests, but most crops have shallow roots
-Ploughing can kill soil organisms by moving them to depths at which they cannot survive
Abiotic factors & their control- aeration; how can aeration be controlled?
-Ploughing turns over & aerates surface soil layers but not deeper layers
-Adding organic matter provides food for soil biota that increase aeration
-Low tillage methods prevent;disturbance to soil & killing of soil organisms during ploughing
-Removing livestock from fields when soil is very wet reduces compaction caused by trampling
Abiotic factors & their control; why is soil salinity good and bad?
Dissolved salts in soil water are essential for plant growth as they include soil nutrients but excessive salinity can kill plants by osmotic dehydration of their root
Abiotic factors & their control- soil salinity; how can soil salinity be controlled?
-Main method is to avoid farming methods that increase salinity, esp irrigating w/ groundwater that has a high salt content
-Salt concentration of soil increases as salts are left in soil when water evaporates from it
-Extra water can be used to wash salts out of soil but this greatly increases water consumption & can cause ecological problems by increasing salinity of local river
Abiotic factors & their control; how does pH impact soil?
-All plant species have their own range of tolerance for pH, usually between pH5 & pH7
-A high pH can inhibit nutrient solubility
-A low pH can increase leaching of nutrients & inhibit nutrient uptake. It can also mobilise toxic ions in soil like aluminium & lead
Abiotic factors & their control; how can soil pH be increased and reduced?
-Increased; adding crushed lime (calcium carbonate/hydroxide)
-Reduced; spreading powdered sulfur
Abiotic factors & their control; how does carbon dioxide concentration affect agriculture and how can this be controlled?
-CO² concentration can be the limiting factor on the rate of photosynthesis
-It’s not practical to increase CO² concentrations for crops grown in fields
-However, crop growth rates in greenhouses may be increased by burning carbon-based fuel like gas/paraffin
-The CO² is kept in the greenhouse rather than being lost & increased costs may be justified by high market value of greenhouse crops
Abiotic factors & their control; in what ways can topography affect agriculture?
Undulations of the land surface can affect its suitability for particular crops & methods used;
-Aspect; undulations, eg valleys, produce some areas more exposed to sunlight & tend to be warmer
-Frost pockets; cold dense air may collect in low-lying areas, making crop frost damage more likely
-Runoff rate; steeper gradient make soil erosion by surface runoff more likely. Gentle/flat gradients make flooding more likely
-Use of machinery; may be difficult to operate large machinery on land that undulates a lot/where gradients are very steep
Abiotic factors & their control; how can topography be controlled?
-It’s not practical to alter the topography of large areas of land but it may be possible in some areas
-An area of steep gradient may be changed to a series of flat fields by terracing
-This is usually done to retain irrigation water & reduce soil erosion
-Areas that are nearly flat may be levelled by machinery so that water drains slowly; can reduce irrigation needs & help produce flooded fields for rice cultivation
Abiotic factors & their control; what is relief and how can it affect agriculture?
Altitude of an area controls other factors that affect the choice of species for cultivation, eg
-Crops; temps are often colder at higher altitudes. The low atmospheric pressure increases evaporation rate
-Livestock; some species are adapted to high altitudes like goats, sheep & llamas. They can survive lower temps & low atmospheric pressures. Cattle don’t thrive at high altitude as the low atmospheric pressure causes ‘high altitude disease’ where pulmonary arteries thicken
-It’s not possible to control the relief of an area
Abiotic factors & their control; what issues do high wind velocities cause and can it be controlled?
-Increased soil erosion, esp dry areas
-Increased evaporation rates & drying of soils
-Crop damage eg ‘lodging’ of cereal crops when they’re flattened by strong winds
-Wind velocity can be controlled by windbreaks like hedgerows/rows of trees
Biotic factors & their control; how does agriculture impact the previous natural ecosystem?
-Removes most of it & replaces it w/ a simpler agricultural ecosystem, dominated by the crops & livestock
-Some wildlife species take advantage of the new community of species & may become pests, esp if their natural predators are no longer present
-Other species that provided important services may become less common, eg crop pollinators & soil organisms that recycle nutrients
Biotic factors & their control- pest control; what are pests and how do they impact agriculture?
-Organisms that reduce agricultural productivity/quality of the product by;
-Being predators that eat the crop/livestock
-Competing for resources like water/nutrients
-Being pathogens that cause disease
-Carrying pathogens
-Reducing marketability, eg spoiling appearance of fruit/by weed seeds mixing w/ cereal harvest
Biotic factors & their control- pest control; what problems do weeds cause + examples?
-Competition for nutrients, water light, eg wild oats in cereal crops
-Harvested w/ the crop, reducing quality/spoiling taste
-Provide food for other pests
-Parasitism of crop roots eg strings parasites maize crops
Biotic factors & their control- pest control; what problems do insects cause + examples?
-Eat the crop, destroy the crop, or reduce harvests
-Spoil the appearance of harvested crop eg aphids (like greenfly & blackfly) suck the sap + reduce growth of many crops like cotton
-Act as vectors & spread pathogens. Aphids carry many pathogenic diseases eg potato blight
Biotic factors & their control- pest control; what problems do fungi cause + examples?
-Cause the growing plants/harvested crop to rot
-Eg leaf smut (of rice) & leaf blight (of sugarcane)
Biotic factors & their control- pest control; what problems do bacteria cause + examples?
-Reduce harvests by causing disease
-Eg bacterial wilt (of potatoes) & bacterial leaf blight (of wheat)
Biotic factors & their control- pest control; what problems do molluscs cause + examples?
-Eat the crop, reduce harvests, or spoil appearance
-Eg many snails & slugs
Biotic factors & their control- pest control; what problems do nematode worms cause + examples?
-Damage roots & reduce water + nutrient uptake
-Increase risks of fungal & bacterial disease
-Eg potato cyst nematode & soybean cyst nematode
Biotic factors & their control- pest control; what problems do vertebrates cause + examples?
-Eat the growing/harvested crop
-Eg mammals; mice, rats, deer, rabbits. Birds, eg sparrows, quelea
Biotic factors & their control- pest control; when are endemic and epidemic species present?
-Endemic pests are always present, usually in small/moderate numbers
-Epidemic pests are not normally present but there may be ‘outbreaks’ where they rapidly become a major problem
Biotic factors & their control- pest control; what are indigenous and introduced pests and why are they an issue?
-Indigenous species are native to the area where they are found
-Many pests have been introduced from other areas; are often more of a problem as may not have any predators in the new areas
Biotic factors & their control- pest control; what does cultural pest control involve?
Non-pesticide methods where crops/livestock are cultivated in a way that reduces risk of pest damage, often by using natural ecosystem services
Biotic factors & their control- pest control; what is crop rotation and why is it done?
-Different crops often have their own unique pest species
-If the same crop is grown in the same place in consecutive years then pests from the first year may survive until the second year so pests are already present & don’t need to colonise from elsewhere
-This allows pest population to increase earlier in the year & cause more damage
-Crop rotation involves the cultivation of a different crop each year, usually on a four/five year cycle
-Pests remaining at the end of one year will have died off before that crop is grown again
Biotic factors & their control- pest control; what are companion crops and why are they beneficial?
-These are crops which, if grown together, will be more productive
-Sometimes both crops will produce a harvestable crop
-In other cases, one of the plants is only grown because the harvest of the other one will be increased
Biotic factors & their control- pest control; what are the different inter-species relationships between companion crops?
-Nutrient supply; legumes can be intercropped among other crops to increase nitrate availability in soil
-Barrier crops; smell of onions can mask smell of carrots & reduce damage
caused by carrot root flies
-Pest attraction to protect the other plants; nasturtiums attract blackfly pests that could damage bean crops
-Support of pollinators; flowering plants that support bees which are important in pollinating fruit crops
Biotic factors & their control- pest control; why are pest predator habitats provided and what are examples of these?
-Populations of natural pest predators can be increased by providing suitable habitats
-Beetle banks & hedgerows provide habitats + hibernation sites for pest predators like black ground beetles & ladybirds that eat aphids like greenfly & blackfly
Biotic factors & their control- pest control; what is biological control and why is it carried out?
-Predator/pathogen species may be introduced to control pests
-This is especially important if pest is a non-indigenous species that has been introduced & has no indigenous predators
-Biological control species should be selected carefully; should be specialist feeders that will eat pest species. If they have a wider diet they may eat beneficial & other non-target species
Biotic factors & their control- pest control; what are examples of successful and unsuccessful biological controls?
-Successful; Whiteflies in greenhouses have been successfully controlled by the introduction of parasitic Encarsia wasps
-Unsuccessful; Cane Toads were introduced to Australia to control beetle pests of sugar cane but they’ve eaten a wide range of other species. They’re toxic so have few predators & have colonised a huge area
Biotic factors & their control- pest control; what are sterile male techniques of pest control and why are they carried out?
-In many insect species, females only mate once then store sperm for all future egg laying. If a female mates w/ a sterile male then she will never produce any offspring
-Method involves producing many sterile males by exposing them to gamma radiation, then releasing
-If enough sterile males are released then number of fertile matings will be reduced to level below that needed to produce enough young to compensate for mortality, so population would decline
-Pests that have been controlled by sterile male techniques include; Screw Worm Fly (an important parasitic pest of livestock in Central America), Mediterranean Fruit Fly, Sweet Potato Weevil in Japan
Biotic factors & their control- pest control; what are advantages/disadvantages of sterile male techniques
-It’s species-specific so doesn’t affect non-target species
-It’s only successful if sterilised males behave normally & succeed in finding mates
-In some projects, eg those w/ mosquitoes, process of sterilisation of males w/ radiation alters their behaviour so that females reject them & still mate w/wild fertile males
-Re-colonisation from nearby areas that haven’t been cleared may require regular re-treatment
Biotic factors & their control- pest control; what are pheromone traps and examples of them?
-In many insect species, mates are attracted by a scent called a pheromone
-Pheromone traps release an artificial scent that attracts pests; males/females, depending upon species
-Can be used in two ways; to show the pest is present so that pesticides can be used to protect crop & to kill all pest individuals/enough of one gender of the pest so that there aren’t enough fertile matings to maintain pest population. Normally only works in enclosed areas like greenhouses
-Pheromone traps are used for a wide range of pest taxa incl moths, weevils & flies
Biotic factors & their control- pest control; how does genetic resistance control pests + examples?
-Within any species there’s a range of genetic characteristics for every environmental adaptation
-Selective breeding may enhance resistance of a variety to pests/disease
-Pathogens evolve to overcome crop disease resistance so it’s necessary to regularly introduce new characteristics to maintain resistance
-Commercially cultivated crops often have little genetic diversity so search for new characteristics must focus on wild varieties & CWR (Crop Wild Relative) species/traditional crop varieties often grown by subsistence farmers
-All these genetic resources are threatened by habitat loss & spread of commercial crop varieties w/ small gene pool
-Eg Boran cattle in East Africa are more resistant to protozoan disease East Coast Fever than most other cattle breeds
Biotic factors & their control- pest control; how can GM crops
DNA of a crop can be modified to control pests more effectively by reducing susceptibility to pest
Biotic factors & their control- pest control w/ chemical pesticides; how does toxicity impact a pesticide?
-Pesticides which have high toxicity require use of smaller volumes
-Most pesticides act by inhibiting enzyme action
Biotic factors & their control- pest control w/ chemical pesticides; what is specificity and how does it impact the pesticide?
-Measure of range of taxa affected by pesticide
-More specific pesticides are less likely to harm non-target species
Biotic factors & their control- pest control w/ chemical pesticides; how does persistence impact a pesticide?
-Persistent pesticides are chemically more stable & degrade slowly
-This reduces frequency of re-application but can increase likelihood of a pesticide dispersing more widely in the environment & may extend time period that it may harm non-target species
Biotic factors & their control- pest control w/ chemical pesticides; how does solubility in water/lipids impact a pesticide?
-Pesticides that are water soluble are more likely to be washed off a crop, requiring re-application
-Liposoluble pesticides may be absorbed & stored within the crop, possibly entering the human food chain
Biotic factors & their control- pest control w/ chemical pesticides; what are the two main modes of action with which chemical pesticide kill pests?
-Contact action; contact herbicides kill plants by damaging tissues they’re sprayed onto. Contact insecticides kill insects that are sprayed directly/come in contact w/ pesticide that was sprayed onto crop that’s being protected. Pesticide only protects crop surfaces that are sprayed. Unsprayed surfaces aren’t protected, eg undersides of many leaves/new growth. They may also be washed off by rain
-Systemic action; systemic pesticides are absorbed by crop & translocated throughout plant. This protects all of the plant & will protect new growth.
Pesticide can’t be washed off by rain but can be retained in harvested crop & eaten by humans
Biotic factors & their control- pest control w/ chemical pesticides; what are antibiotics and why are they used in livestock farming?
-Chemicals that kill microbes like pathogenic bacteria
-To treat infections; course of antibiotics may kill pathogenic bacteria
-To prevent infection; regular large doses of antibiotics may prevent livestock from becoming infected w/ pathogenic bacteria. May be done as precaution, esp where livestock stocking density is high, like in intensive production
-To promote growth; antibiotics can be used to increase Gross Growth Efficiency of livestock. Regular small doses of antibiotics reduce population of non-pathogenic gut bacteria. This can increase the amount of animal’s food that’s used for growth, thus increasing productivity & farm income
Biotic factors & their control- pest control w/ chemical pesticides; what are the advantages and disadvantages of using antibiotics in farming?
-Use of antibiotics in agriculture > amount used in human healthcare
-Exposure to a high dose of an antibiotic may kill all of a pathogen population
-Exposure to a lower dose may only kill most sensitive individuals so surviving population will be less easily controlled by antibiotic
-Large scale use of antibiotics as growth promoters increases risks of producing antibiotic resistant bacteria. Some of these may be zoonoses which cause disease if are transferred to humans, eg E. coli, Salmonella & Campylobacter
Biotic factors & their control- pest control w/ chemical pesticides; how do hormone pesticides work and what are their advantages?
-Kill pests through their biochemical action. However, they don’t kill via toxic action but by increasing/starting natural processes in a way that’s harmful to pests
-Insect hormone pest control chemicals control development in a way that causes death
-Some hormones cause insects to metamorphose into adults before they’re large enough to function properly so they die. Others prevent formation of the chitin skeleton when they moult
-Have low persistence & are more specific than most pesticides
Biotic factors & their control- pest control; what is integrated control and why is it advantageous?
-Each pest control technique has its own particular advantages & disadvantages
-Use of a combination of techniques can maximise effective pest control while minimising environmental impacts
-Often has an order in which techniques are used based on cost & ease of use, effectiveness & environmental impacts
Biotic factors & their control- pest control; what are the principles of integrated control?
-Use of cultural techniques which make growth environment less suitable for pests, eg maintaining habitats for indigenous predators
-Use of cultural techniques that prevent build-up of pest population, eg crop cutivating species & varieties that are less likely to suffer pest attack
-Use of other appropriate non-pesticide techniques
-Use of pesticides when essential; carefully timed applications of specific, non-persistent pesticides
Biotic factors & their control- pollinators; how can the services of pollinators be aided?
-Provision of food supplies by growing plants that provide nectar, eg mix of
flowering plants alongside crop
-Restricting use of pesticides that harm pollinators
-Introduction of bee hives
Biotic factors & their control- maintenance of soil biota; what are the roles of soil biota and why are they important?
-Are important for soil fertility & crop productivity, esp detritivores + decomposers
-Increase nutrient availability through breakdown of dead organic matter & nitrogen fixation
-Organic acids produced by decomposition increase weathering of rocks that releases nutrients into soil
-Earthworms increase aeration & drainage which aid aerobic processes + water retention
Manipulation of food species- population control; how can population density aid crops?
-Increasing population density can increase total yield, although yield per individual may be reduced due to inter-species competition
-A high population density can increase risk of rapid spread of disease
Manipulation of food species- population control; what are monocultures and how can they be good & bad for cultivation?
-Involves cultivating a single species, often over a large area
-Can make cultivation easier by allowing use of larger machinery but pests & diseases can spread rapidly if they colonise the field
-Removal of hedgerows & other habitats to create larger fields can also increase pest damage as natural predator habitats are lost
Manipulation of food species- control of genetics; what is natural & artificial asexual reproduction in plants?
-In natural asexual reproduction, the offspring develop from the parent plant rather than from seeds, eg strawberry plant ‘runners’
-Artificial asexual reproduction involves cuttings where new plants are produced from sections of leaf/stem/root tissue from parent plant
Manipulation of food species- control of genetics; what are the advantages and disadvantages of plant asexual reproduction?
-Advantages; offspring are genetically identical to parent plant, so their characteristics are predictable. The survival rate is high
-Disadvantages; there’s no genetic variation in the offspring so their characteristics can’t be improved. Fewer offspring are produced than by sexual reproduction
Manipulation of food species- control of genetics; how is asexual reproduction done in animals and what is the method?
-Cloning is an artificial asexual reproduction technique for livestock that’s still being developed
-Aim is to produce offspring that are genetically identical to a selected individual w/ desirable characteristics; the donor
-Method; cells are removed from donor & grown in culture. An egg is removed from a female. Nucleus of egg is removed & replaced by nucleus from one of the donor cells. Egg is implanted into a surrogate female where it develops during a normal pregnancy. When it’s born it has the characteristics of the donor
Manipulation of food species- control of genetics; what are the potential applications of animal asexual reproduction to agriculture?
-Valuable animals that die can be replaced by genetically identical individuals
-Herds that are culled during a disease outbreak can be replaced w/ genetically identical individuals
-Large numbers of individuals w/ desirable characteristics could be produced
Manipulation of food species- control of genetics; what does selective breeding in sexual reproduction involve and why is it done?
-Production of offspring from parents that were chosen due to their genetic characteristics. Eg Highland Cattle; even temper, few stress problems, hardy
-Breeding betw genetically similar individuals may produce offspring w/ similar characteristics, but there’s an increased risk of inbreeding
Manipulation of food species- control of genetics; why is crossbreeding undergone and what is an example of a case study?
-Crossbreeding betw two different parental breeds may produce a combination of desirable characteristics w/ ‘hybrid vigour’ & lower risk of inbreeding
-Reduces problems caused by homozygous recessive genes often found in inbred varieties. This is called ‘hybrid vigour’/heterosis
-Eg; Zebu cattle which are reared in areas w/ a hot climate. They tolerate heat well but give a low milk yield. Ayrshire cattle from Scotland give a very high milk yield but they aren’t heat tolerant. Crossbreeding betw Zebu & Ayrshire cattle has produced cattle that can tolerate heat & have a high milk yield
Manipulation of food species- control of genetics; what is artificial insemination and why is it an example of an improved breeding technique?
-Semen collected trom a male who has desirable characteristics is used to impregnate females
-Many more young can be produced than by natural mating
-Frozen semen samples can be transported much more easily than parents & can be stored so offspring can be produced long after male has
died
Manipulation of food species- control of genetics; what is embryo transfer and why is it an example of an improved breeding technique?
-Hormone FSH is used to stimulate ovulation & release of many eggs by a female
-Eggs are washed out of the uterus & collected, then fertilised by sperms collected from a male w/ desirable characteristics (IVF)
-Each fertilised embryo is implanted into a different surrogate female
-Donor female can produce multiple embryos more frequently than she could produce offspring via normal pregnancies
Manipulation of food species- control of genetics; what is genetic engineering/genetic modification (GM) and what does it allow?
-Alternative names for the other previous genetic procedures
-Potential benefits are very large but there are concerns about environmental impacts
-Conventional selective breeding programmes can only introduce characteristics that exist within the gene pool of the species/other species very closely related & can produce fertile hybrid offspring
-Allows introduction of single characteristics from one species to another/betw varieties or breeds of same species
-Range of new GM varieties has been developed but concerns over environmental & human health impacts have prevented many entering commercial cultivation
Manipulation of food species- control of genetics; what are some genetic engineering/genetic modification (GM) case studies?
-Bt crops; bacterium Bacillus thuringiensis naturally produces a toxin that kills insects. The gene that controls production of the toxin has been transferred into crops like corn, cotton & maize so that toxin protects crops from insect pests
-Golden rice; diet that’s deficient in Vitamin A causes about 500 000 new cases of blindness each year, espe in India/sub-Saharan Africa. Rice contains vitamin A, but it’s in the husk that’s often removed so that rice grains can be stored. Genes have been transferred from the daffodil & soil bacterium (Ervinia uredovora) so that vitamin A is produced within rice grains. The rice grains have a yellowish colour, hence name Golden Rice
Manipulation of food species- control of genetics; what are the advantages of genetic engineering/genetic modification (GM)?
-Individual desirable characteristics can be introduced w/out associated unwanted characteristics, as can occur in normal selective breeding
-Genes may be introduced from other species that couldn’t have been achieved by normal selective breeding
-Can increase resistance to specific insects, reducing amount of pesticides used to protect a crop
-Can increase pathogen resistance reducing disease in a crop
Manipulation of food species- control of genetics; what are the disadvantages of genetic engineering/genetic modification (GM)?
-Relatively new technology, concerns over potential problems have delayed the general use of GM crops. More evidence to fully assess risks
Potential risks claimed for use of GM crops;
-Has been claimed that GM food can increase food allergies
-Potential gene transfer from GM foods to cells of body/bacteria in gastrointestinal tract
-Migration of genes from GM plants into conventional crops & plants. Eg, pollen from GM crops may contaminate organic crops & spread to closely related wild varieties that could have ecological impacts, like if Bt gene entered gene pool of wild plants then insects that feed on them may be killed
-Transfer through food chain, eg GM crops approved for animal feed/industrial use being detected at low levels in products for human consumption
-Genes that provide resistance to antibiotics are often inserted w/ desired genes. Act as ‘markers’ & are used to check whether the gene transfer has been successful. Cells into which genes have been transferred successfully won’t be harmed by antibiotic. There’s some concern that antibiotic resistance gene present in food may transfer from GM crops to pathogenic bacteria, making disease harder to treat
-Increased costs to farmers esp in LEDCs as many GM crops require new seeds to be purchased each year rather than harvesting seeds from existing crop. Intellectual Property rights and patents for specific GM crops are owned by specific companies who control prices & availability of seeds
-Concerns in LEDCs that GM crops will reduce local indigenous crop diversity including successful seed saving practices
Agricultural energetics- intensive and extensive agriculture; what is the intensity of agriculture is a measure of?
-A major aim of agriculture is to produce more food than would be produced by previous natural ecosystem but this requires inputs of materials & energy
-The intensity of agriculture is a measure of the amount of artificial inputs & extra yield that’s produced
Agricultural energetics; what is intensive and extensive agriculture and how do they differ?
-In extensive agriculture, the aim is to maximise total yield by spreading available inputs over a large area of available land
-Intensive agriculture is practised where large inputs are available but there may be a shortage of land. Yields per unit area may be very high but extra yield per unit of input may not be
-So, although intensive agriculture may be very productive, it’s not necessarily very efficient
Agricultural energetics- intensive and extensive agriculture; what is the law of diminishing returns and how can it be applied?
-Link betw intensity of farming, efficiency & productivity is demonstrated by the law of diminishing returns
-Each extra unit of input results in an increase in yield but size of each successive increase gets smaller. If enough suitable land were available, then spreading inputs evenly over total area would produce a greater overall yield than concentrating all inputs onto a small area
-Principle could be applied to global food production system. Total yield would be increased if intensity of agriculture were reduced in some areas, w/ unused inputs being used on land that’s currently farmed extensively
-Uneven investment of inputs may be sensible in some situations, eg where one area has potential to be much more productive. However, sometimes uneven use of inputs is purely economic, w/ more affluent societies having ability to buy more while poorer communities that could benefit greatly from access to more inputs can’t afford them
Agricultural energetics; what is an energy subsidy in an agricultural system?
Any input that aids productivity but requires use of energy
Agricultural energetics- energy subsidies; what do major agricultural energy subsidies include?
-Manufacture of nitrate fertilisers
-Manufacture of pesticides
-Pumping of irrigation water
-Fuel for machinery for ploughing, spraying, harvesting
-Energy for manufacture of machinery & equipment
-Heat for drying harvested grain
-Processing of food for consumers
-Transport of food to consumers
Agricultural energetics- energy subsidies; why may energy subsidies not be reliable?
-As agricultural systems have become more productive and more intensive, they’ve become increasingly dependent on energy subsidies, esp energy from fossil fuels
-It may be difficult to maintain/increase food production if abundant energy supplies can’t be maintained
Agricultural energetics; what are energy ratios?
-Measure of efficiency by comparing energy inputs & outputs, then expressing this as the number of units of food energy produced per unit of energy input
-Systems that give the highest yields per unit of energy input have higher energy ratio values
-Isn’t the same as productivity per unit area. A system w/ a high productivity may require high energy subsidies & therefore have a low energy ratio
Agricultural energetics; what are food conversion ratios (FCR) and what do they indicate?
-Measure of mass of food needed to produce given mass of livestock growth
-The lower the ratio, the better the conversion of food into animal biomass
Agricultural energetics- control of food chain energy losses; what are autotrophs and autotrophic nutrition?
-All living organisms need chemical energy to drive biological metabolic processes. Chemicals that are broken down to release this energy aren’t generally available in the environment but can be built up from simpler molecules by some living organisms called autotrophs (self-feeders’)
-To build up high-energy molecules autotrophs need a source of energy. They use this energy to make carbohydrates like glucose, starch & cellulose + lipids like fats & oils
-Most of these organisms are photo-autotrophs, like plants, algae & photosynthetic bacteria, which capture sunlight during photosynthesis
-Some are chemo-autotrophs, like bacteria that harness energy by oxidising substances eg hydrogen sulfide, methane, & ions of ammonium + nitrite
-Autotrophs have a big advantage for survival because they don’t rely on other organisms for their energy supplies. All other organisms rely on autotrophs for their energy supplies
Agricultural energetics- control of food chain energy losses; what are heterotrophs and heterotrophic nutrition?
-Organisms that can’t produce their own high-energy molecules must gain their energy from other living organisms. These are heterotrophs (different-feeders) which include all animals, fungi & many bacteria
-Much of the energy captured by autotrophs is used in their metabolic processes & released back to the environment as low energy-density heat
-So, amount of energy available to heterotrophs is much less than was harnessed by autotrophs
-In a food chain w/ several trophic levels, less energy is passed on to next trophic level than was received from previous one. This is why few food chains have 4+ trophic levels
Agricultural energetics- control of food chain energy losses; how can productivity be achieved despite food chain energy losses?
-As amount of energy in a food chain declines w/ each progressive trophic level, amount of food that can be prepared by an agricultural system depends upon which trophic level produces the food
-So, in general, greatest possible amount of food produced by an area would be plant material rather than meat
-If an area of land can grow crops that can be eaten by people then this’d be the most productive system. In some areas this isn’t possible, eg upland/semi-arid areas where permanent grassland is a more sustainable land use than arable farmland
-In such areas, best option for food production is to raise grazing animals that can digest grass, like sheep/cattle. They have symbiotic bacteria in their stomachs that produce enzyme cellulose which is needed to digest cellulose in plant material
Omnivores eg pigs can produce edible meat from food wastes that weren’t wanted by people, like the wastes from producing cheese & butter/leftover food from catering industry
Environmental impacts of agriculture- habitat impacts; how does drainage in agriculture cause habitat impacts?
-Farmland is often drained to produce more aerobic soils, eg drainage of waterlogged grassland to increase grass growth
-Wetland plant species & animals they support may not be able to survive the changes
Environmental impacts of agriculture- habitat impacts; how does nutrient enrichment in agriculture cause habitat impacts?
-Using fertilisers increases nutrient availability & plant growth rates
-Species that respond by growing taller like grasses may out-compete smaler plants, eg many wildflower species
Environmental impacts of agriculture- habitat impacts; how does reduced biodiversity in agriculture cause habitat impacts?
-Natural ecosystems often have small-scale local variations in abiotic factors producing differences in composition of community of species found there
-Agroecosystems often replace diverse communities of indigenous species w/ a community of species that has fewer species, many of which may not be indigenous
-Many indigenous species won’t be able to survive new conditions/may be removed as they’re predators/competitors
Environmental impacts of agriculture- habitat impacts; why can agriculture also create new habitats?
-Agriculture doesn’t just destroy habitats. It can also create new habitats which may be gradually colonised by wildlife species
Some areas that have been farmed in the same way for long periods of time have become plagioclimax habitats that are valuable to wildlife. Eg; hedgerows, hay meadows, grazed moorland and heathland, chalk grassland
Environmental impacts of agriculture- introduced species; how has farming introduced pests + examples of this?
-Farming has introduced many species into new areas where they wouldn’t naturally be found
-Some are crop/livestock species that have colonised the surrounding area & become pests, others are pests that have been introduced accidentally like the late blight fungus of potato & tomato crops
Environmental impacts of agriculture- introduced species; how have biological control species been used for pests and why may this be an issue?
-Biological control can be used to control pests instead of using pesticides, which should reduce environmental damage
-However, introducing non-indigenous species can cause problems
-Introduced predators may eat other species as well as the pests
Environmental impacts of agriculture- pollution; how do pesticides cause environmental impacts in agriculture?
-Pesticides are deliberately used as they’re toxic & are intended to kill pests
-As pesticides aren’t species-specific, sensitive non-target species may also be killed
-Species may also be affected if inter-species relationships are affected like the death of food species, pollinators, or pollution that favours competitor species
Environmental impacts of agriculture- pollution; how can nutrient pollution in agriculture cause environmental impacts?
-Nutrients that were intended to stimulate crop growth/are digestive wastes from livestock, can stimulate growth of undesirable organisms
-Leached inorganic nutrients cause eutrophication, eg nitrate fertilisers
-Organic nutrients like manure can cause deoxygenation of rivers & lakes due to the aerobic respiration of bacteria
Environmental impacts of agriculture- pollution; how can nitrate toxicity cause environmental and health impacts?
-Nitrates can be leached from farmland into water bodies that are used as sources of potable water for human consumption
-High nitrate levels can cause blue baby syndrome (methaemoglobinaemia) & nitrates may be a human carcinogen
Environmental impacts of agriculture- pollution; how can agriculture contribute to climate change?
-Several farming activities release greenhouse gases
-Carbon dioxide; fossil fuel use, ploughing increases soil aerobic respiration
-Methane; microbial anaerobic digestion, livestock intestines, rice padi fields
-Oxides of nitrogen (nitrous oxide); from livestock manure & nitrogen fertilisers
Environmental impacts of agriculture- pollution; how can embodied energy cause environmental impacts in agriculture?
Manufacture of materials, esp nitrate fertilisers & machinery, usually involves use of fossil fuels & causes release of GHGs, mainly carbon dioxide
Environmental impacts of agriculture- changes in the hydrological cycle; what impacts on the hydrological cycle has agriculture had?
-Irrigation water can deplete the sources of the water, eg aquifers/rivers
-Soil erosion caused by agriculture can reduce effect that soil has on the hydrological cycle like water retention & moderation of extremes in river flow
-Soil compaction can increase runoff rates & cause more rapid fluctuations in river flow
-Agriculture changes evapotranspiration rates but actual change depends on ecosystem that was present before farming started. Evapotranspiration is increased in arid areas but may be reduced in areas where forests were removed
Environmental impacts of agriculture; how can agriculture cause soil erosion?
-Soil is the growing medium in almost all agricultural systems
-Soil erosion is a natural process but poor soil management can lead to the rate of erosion exceeding rate of formation, so amount of soil present declines
Social factors that affect agriculture; how do cultural factors affect agriculture?
Horse meat isn’t popular in the UK but is widely eaten in other
European countries
Social factors that affect agriculture; how do religious factors affect agriculture?
-People w/ religious convictions may avoid certain foods
-Jews & Muslims don’t eat pork while Hindus don’t eat beef
Social factors that affect agriculture; how do ethical issues affect agriculture?
-Local food/food miles; buying food that was produced nearby reduces energy involved in transport & pollution that would’ve caused
-Seasonal food; choosing food that’s grown when local weather is suitable has lower environmental impact than eating out-of season food that needs heating, lighting, transporting from another area w/ a suitable climate
-Free-range livestock; some consumers choose to buy eggs & meat from animals that are kept under conditions close to their natural conditions, especially having freedom to move around & search for food. They often consider conditions of intensive rearing to be cruel
-Organic food; some consumers choose to buy food that was produced using natural processes wherever possible rather than those using artificial processes for pest control & nutrient supply
-Fair trade food; fair trade food is produced in a way that provides an income for producers which means that they can afford basic human rights like water, education, health care & food
Availability of technology; how does the availability of technology affect agriculture?
-Productive agriculture benefits from the development & availability of a wide range of technologies
-These are usually more available in more affluent societies
Availability of technology; what are the range of technologies that agriculture benefits from in more affluent societies?
-Machinery & equipment for activities like ploughing, sowing, spraying, harvesting, spreading agrochemicals + irrigation
-Pesticides
-Fertilisers
-Genetic improvements through breeding programmes
-Support infrastructure like transport systems, refrigeration, food processing
Availability of technology- survey technology; what range of factors are GPS mapping & the use of drone and satellite surveys used to monitor?
-Rates of photosynthesis
-Biomass estimation
-Soil water content
-Spread of pests & diseases
-The cropped area of the fields, area of cover for wild birds, tree plantations etc
Economic & political influences on agriculture; how has food aid influenced agriculture after 1945?
-After the war, Europe couldn’t produce enough food to feed everyone
-W/out a major change in food availability there would’ve been serious food shortages, possibly famine & social + political problems
-Food aid from the USA helped to reduce these problems
Economic & political influences on agriculture; how have grants influenced agriculture after 1945?
-At that time, farmers in Europe couldn’t afford to invest in more productive methods as they weren’t sure they’d earn enough to repay the loans they would’ve had to take out
-To solve this, grants were made available so farmers could get financial assistance for a wide range of projects to increase food production like; hedgerow removal to increase field size, purchase of machinery, drainage of wet fields, improved livestock & liming to neutralise acidic soils
-These changes increased food production but had environmental impacts like the loss of hedgerows & wetlands
Economic & political influences on agriculture; what is the ‘guaranteed market’ and how has this helped farmers?
-Increasing production eventually created a new problem; if output exceeded demand, then market price would drop & farmers could make a loss, despite high yield
-To solve this issue greater financial security was given to farmers by providing a ‘guaranteed market’ w/ a price-support system
-If there was a surplus harvest the gov would buy some of the harvest from farmers to create an artificial market shortage & raise the price to an agreed level that’d been set earlier in the year
-Where possible, the surplus would be stored, eg grain, milk powder, cheese, meat. Surplus food that couldn’t be stored was often destroyed, eg fruit & vegetables
-If there was a poor harvest then shortages in supply could’ve caused prices to rise
-The gov prevented this by selling just enough food that’d been stored from previous years to bring market price down to the agreed level. This system created more financial stability for farmers & consumers, helped to raise food production
Economic & political influences on agriculture; why were food surpluses an issue after the 1970s and why was this difficult to combat?
-By the 1970s, food production had increased to the level where there were more surpluses than shortages in MEDCs
-Farmers continued to grow more food as they had the guarantee that the gov would buy their produce even if consumers didn’t want to buy it
-Gov couldn’t sell surplus food in the normal consumer markets as there weren’t enough years w/ poor harvests
-Finding alternative markets was hard due to competition w/ other food exporters/lack of consumers to buy surpluses
-Surpluses couldn’t be sold to other MEDCs like USA, Canada, Australia as these countries also produced surpluses. Japan was an MEDC that imported food but already had established suppliers eg the USA & Australia
-Countries of Eastern Europe & the USSR needed food but couldn’t afford to pay full price
-Selling surplus food in LEDCs would undercut local producers, put them out of business & reduce long-term food production
-Only real solution to surpluses was to avoid producing them but this involved big changes in the way agriculture was supported by EU & national govs
Economic & political influences on agriculture; what methods have governments used to reduce excessive food production while hopefully maintaining farm incomes?
-Quotas; farmers are given limits on what they’re allowed to produce, eg dairy farmers are given a limit on amount of milk they can sell
-Farm diversification; farmers have been encouraged to concentrate less on products that were being over-produced & more on new products + non-food production activities like recreation, public visits to working farms & specialised dairy production eg cheese + ice cream
-Alternative crops & livestock; biofuels, pharmaceutical crops, eg poppies, llamas, bees for honey & deer
-Set-aside; farmers of crops in surplus have been paid for taking farmland out of production & keeping it in a condition where it could be farmed again if needed
-Agri-environmental schemes; a range of schemes have given farmers a contribution to their income for farming in ways that benefit the environment, eg Environmentally Sensitive Areas (ESAs), Countryside Stewardship Scheme (CSS), Environmental Stewardship Scheme (ESS), Countryside Stewardship (CS)
Economic & political influences on agriculture; what are some examples of aspects and requirements of agri-environmental schemes?
-Hedgerows; must be at least 1.5m tall, no fertilisers/pesticides to be applied within 2m, at least 2yr interval betw cutting & no cutting during bird breeding season. Purpose; to maintain habitats for birds & insects, restore traditional patchwork of fields
-Trees; conservation of in field trees. Purpose; conserve soil, energy, water, wildlife, atmosphere & protect ancient indigenous trees
-Planting; selected plants for nectar & seeds. Purpose; to support pollinating insects & provide winter food for seed-eating birds
-Nesting plots; provision of skylark nesting plots in fields. Purpose; maintain & increase skylark populations
Strategies to increase agricultural sustainability; why is there a need to increase agricultural sustainability?
-Food is a basic requirement for survival
-W/ a growing human population, it’s increasingly important that food supplies also increase
-Population size of most species is controlled by density-dependent factors like disease & food supply
-If population rises above carrying capacity of environment then death rate increases & population is reduced
-Only humans can consciously manipulate the environment to produce more food & allow population to rise above natural carrying-capacity
-It wouldn’t be possible to support the huge global human population w/out directing more of energy captured by photosynthesis into the human food chain & so artificially raise food output of the agricultural system
-The growing human population will probably reach at least 12b during this century. This’ll make the sustainable management of food production even more important
Strategies to increase agricultural sustainability; how can the development of sustainable agricultural systems be guided by learning from past mistakes?
-Agriculture first developed about 12,000 years ago in the fertile crescent
-This is an area of the Middle East, largely in the modern countries of Iraq and Syria. It was an area w/ diverse habitats
-It included forested areas w/ a good climate & fertile soils which made it suitable for food production + more fragile grassland, semi-desert areas
-Natural climate change & the way in which land was exploited has gradually reduced capacity of the land to produce food
-Similar reductions in productivity have occurred in many areas like the mid-west of the USA, parts of the UK, deforested rainforest areas, and large areas of Africa
Strategies to increase agricultural sustainability; how has the response to problems from land degradation often involved strategies that increase productivity but may be unsustainable in the long term?
-Key features of land degradation are often soil erosion combined w/ a reduction in soil nutrient & water levels
-Reduction of natural biodiversity often makes pest problems worse
Responses;
-Reliance on artificial fertilisers for nutrient supplies
-Reliance on chemical pesticides for pest control
-Irrigation using water from groundwater resources that aren’t being recharged
Strategies to increase agricultural sustainability; what is organic agriculture?
-Often described as the practices that aren’t done, eg not using pesticides & artificial fertilisers
-This misses the point. Organic agriculture uses natural processes to provide nutrients, control pests & provide ecological services so that the use of pesticides + artificial fertilisers is unnecessary
Strategies to increase agricultural sustainability; how does pest control pose a sustainability problem and what are sustainable strategies to solve this?
-Reliance on chemical pesticides may be unsustainable
-Use of some pesticides has been banned/restricted due to their impacts on non-target species
-Many pests have developed resistance to pesticides
-Strategies; cultural pest control: weeding, mulching, crop rotation, barrier crops, culling, biological control, predator habitats, polyculture/companion crops + integrated control & reduced use of antibiotics
Strategies to increase agricultural sustainability; how do nutrient supplies pose a sustainability problem and what are sustainable strategies to solve this?
-Current supplies of rock phosphates to produce phosphate fertilisers are non-renewable
-Strategies; increased use of natural processes to supply nutrients, recycling of organic matter, crop rotation, cultivation of legumes, conservation of soil biota
Strategies to increase agricultural sustainability; how do energy inputs pose a sustainability problem and what are sustainable strategies to solve this?
-Manufacture of nitrate fertilisers requires large energy inputs from fossil fuels
-Strategies; reduced use of artificial fertilisers (especially nitrates), low tillage techniques, low food miles
Strategies to increase agricultural sustainability; how do gene pools for breeding programmes pose a sustainability problem and what are sustainable strategies to solve this?
-Gene pools of Crop Wild Relative (CWR) plants include genes that will be important in future breeding programmes
-Strategies; conservation of habitats that protect CWRs & seed banks to conserve biodiversity
Strategies to increase agricultural sustainability; how do water supplies pose a sustainability problem and what are sustainable strategies to solve this?
-Over-exploitation of rivers & groundwater reserves
-Soil salinisation caused by using saline irrigation water
-Strategies; cultivation of low water-use crops, maintenance of soil + soil organic matter, use of reservoirs + aquifer recharge & drip irrigation rather than overhead sprays
Strategies to increase agricultural sustainability; how do carbon dioxide emissions pose a sustainability problem and what are sustainable strategies to solve this?
-Loss of soil organic matter increases atmospheric CO² levels
-CO² released by fossil fuel use
-Strategies; low-tillage farming to reduce the decomposition of soil organic matter, maintain/increase soil organic matter, reduced use of machinery & use of renewable energy resources
Strategies to increase agricultural sustainability; how do methane releases pose a sustainability problem and what are sustainable strategies to solve this?
-Methane produced by anaerobic microbes in rice padi fields and the digestive systems of livestock
-Strategies; cultivation of rice varieties that can tolerate drier conditions so fields can be drained earlier, feeding cattle a high carbohydrate diet & grinding their food first reduces methane production
Strategies to increase agricultural sustainability; how does wildlife biodiversity pose a sustainability problem and what are sustainable strategies to solve this?
-Loss of species that provide important ecosystem-services eg pest control, nutrient provision & pollination
-Strategies; retain natural + semi-natural ecosystems like hedgerows, ditches, ponds, woodlands & maintenance of soil biota
