agriculture Flashcards
main issues
-impact on biosphere
-use of environmental resources
-pollution
-development and globalisation
-food for human survival
agroecosystem
-farmland is an artificial ecosystem or agroecosystem
-community of species interacting with each other and their physical environment
-controlled by humans
importance of light in agriculture
-better light=more rapid photosynthesis
-day length
-some plants require longer period of light each day for flowering
-other plants require shorter days
-day length affects reproductive function of some livestock species
CONTROL OF LIGHT
-artificial lighting- extended growing season
importance of water in agriculture
-physiological functions- cell turgity
-nutrient absorption- dissolved as ions in water
-used to transport materials- oxygen, glucose, minerals
-transpiration- water leaves via stomata, allows exchange
how does water supply affect crops
-high water requirements- e.g. most rice varieties must be flooded during early growth
-low water requirements- e.g. cereal crops; wheat
-irregular supply- e.g. tomatoes crops can expand and split
-humid conditions- inc risk of fungal diseases
-farmers must consider- amount, reliability, quality
how can we control problems with water supply? (waterlogged soils)
problems-
-fungal disease
-anaerobic dentrifying bacteria
-reduced fertility
solutions-
-excavate drainage areas
-install drainage pipes
-deep ploughing
-avoid soil compaction
how can we control problems with water supply? (drought)
problems-
-inhibits crop growth- transpiration in crops, prevents gas exchange
-eventually death- dehydration inhibits crop biochemistry
-death of livestock
-trampling, compaction, erosion by moving livestock
-desertification
solutions-
-irrigation
-soil mulching
-inc filtration
-reduce soil compaction
-inc organic matter content
what types of technologies benefit agriculture
-machinery and equipment
-pesticides
-fertilisers
-genetic improvements through breeding programs
-support infrastructure
gps mapping, drones and satellite surveys
-rate of photosynthesis
-biomass estimation
-soil water content
-spread of pests and diseases
-cropped areas of fields
how has transport development improved agroecosystem suitability?
-long distance, rapid, bulk transport has become easier
-transportation of perishable foods has become possible
-foods can now be produced in areas where there is no local demand and then transport them to consumers
-relative costs of transporting goods have generally gone down as fuel costs have declined
how has mechanisation improved agroecosystem suitability?
-machinery allows large scale ploughing, spearing of agrochemicals and harvesting
-industries such as food processing, storage and equipment maintenance can support food production
why are nutrients important in agriculture?
-macronutrients-needed in large quantities
-micronutrients-needed in small quantities
-nutrients added to soil after crops are harvested
-nutrients can be added by fertiliser as or natural processes
-nitrogen fixing bacteria:
•rhizobium- symbiotic in root nodules
•azotobacter- lives free in soil weathering
how are fertilisers applied?
organic fertilisers
-faecal manure/sewage
-animal food production wastes
-plant food production wastes
advantages:
-locally sourced
-inc humus layer content
-inc soil biota
disadvantages:
-nutrients compensation can’t be controlled
-expensive to transport
-usually can’t be added to already growing crops
how are fertilisers applied?
inorganic fertilisers
-synthetic fertilisers
advantages:
-control nutrient composition
-nutrients released rapidly
disadvantages:
-leaching
-toxic to detritivores
-doesn’t add organic matter to soils, so humus & biota levels decline
how does topography affect crops?
importance:
-machinery-may be difficult to operate large machinery on land that undulates a lot
-runoff rate-steeper gradients make soil erosion by surface runoff more likely
-frost pockets-cold denser air may collect in low lying areas, crop frost damage
control:
-flat fields by terracing- retain irrigation water & reduce soil erosion
-areas nearly flat levelled by machinery so water drains slowly
how does relief affect crops?
-altitude of an area controls other factors that affect the choice of species for cultivation
-crops-temps are often colder at high altitudes. the low atmospheric pressure increases evaporation rate
-livestock- some species adapted to high altitudes. they can survive lower temps &low atmospheric pressures
control:
-not possible
how does soil aeration affect affect agroecosystem suitability?
-many important soil processes are aerobic such as root respiration, nitrogen fixation, decomposition
-force of gravity compacts soil particles
-counteracted by tunnelling action of detritivores & growth of plant roots
control:
-add organic matter provides food for soil biota
-low tillage methods prevent disturbance of soil
-removing livestock from fields when soil is very wet
how does soil pH affect agroecosystem suitability?
-high pH can inhibit nutrient solubility
-low pH can inc leaching of nutrients & inhibit nutrient uptake
-can be increased by added crushed lime
-can be reduced by spreading powdered sulphir
how does wind velocity affect agroecosystem suitability
-high wind velocities cause several problems:
•inc soil erosion, especially in dry areas
•inc evaporation rates & the drying of soils
•crop damage e.g. ‘lodging’ of cereal crops when they are flattened by strong winds
control:
-windbreaks such as hedgerows or rows of trees
how does soil salinity affect agroecosystem suitability?
-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 roots
control:
-avoid farming methods that inc salinity, especially irrigating with groundwater that has a high salt content.
what biotic factors affect productivity?
agroecosystems
-often a monoculture, very low biodiversity
-indigenous species, both plants & animals are cleared
-however the new ecosystem will be taken advantage of by a new community of species
-pests- any organism that reduces the quality or productivity of crops or livestock in any way
-beneficial organisms-pollinators or soil organisms to recycle nutrients
how can pests damage crops?
-pathogens: reduce harvest due to ill health of the crops or livestock. cause human disease
-competition: reduced harvest due to competition for water, light, nutrients etc
-quality and quantity: reduced quality of harvest (taste, appearance, storability). reduced quantity of harvest
what are the different types of pest?
-endemic pests- always present, usually in small or moderate numbers
-epidemic pests- not normally present but there may be ‘outbreaks’ where they rapidly become a major problem
-indigenous species- native to the area where they are found
-introduced species- found in an area where they aren’t naturally found. these are often more of a problem as they may not have any predators in new areas
different types of pests
-weeds- compensation for resources, provides food for other pests, some species are parasites, draining resources directly from crops, e.g. wild oats in cereal crops and striga parasites maize
-insects- eat and destroy crops reducing harvest, vectors for pathogens, e.g. aphids
-fungi- cause the growing plants or harvested crop to rot, e.g. leaf smut
-bacteria- reduce harvests by causing disease, e.g. bacterial wilt
-molluscs- eat the crop, reduce harvests, or spoil appearance e.g. snails
-vertebrates- eat growing or harvested crop, e.g. mice
why is pest control needed?
-approx 1/3 of wolds food is lost due to pests & associated disease- most serious in low income countries
-pest sometimes is most important for large scale & intensive farming
-monocultures can easily lead to infestation
-intensive farming large numbers of animals kept close together, making disease & pests easier to spread
cultural control methods, advantages and disadvantages
-crop rotation: +prevents build up of pests & diseases specific to certain areas. -requires long term planning
-barrier crops: +help protect soil from wind erosion, reduce top soil loss. -cost, time required to plant during the busy harvest season
-companion crops: +pest control, improved soil health. -competition for resources, inc maintenance
-predator habitats
what are pesticides
-toxic chemicals used to kill pests
-very effective rapid control
-can be longer term problems caused by their use
crop pesticide application:
-spraying of crops in fields
-powder coating of seeds
-soil injection to kill pests in soil
livestock pesticide application:
-dipping of livestock to kill skin parasites
-drenching where livestock drink pesticides to kill internal pesticides
how does toxicity affect pesticide use
-intended to be poisonous to kill pests (target organism)
-may also be poisonous to other organisms
-difference in toxicities to pests & to non target species is important in assessing likelihood of pesticide causing environmental damage
-high toxicity pesticides= smaller volumes
-most pesticides act by inhibiting enzyme action
why is pesticide specificity important
-some pesticides are ‘broad spectrum’ and kill wide range of species
-others are ‘narrow spectrum’ and kill smaller range as they’re more specific
-broad spectrum more likely to kill non target organisms
how does persistence affect pesticide use
-persistent pesticides break down slowly
-more likely to remain in environment for longer periods
-reduces frequency of re-application
-travel long distances
-travel along food chains
how does solubility affect pesticide use
-liposoluble pesticides build up in organisms and food chains
-concentration may build up until it’s toxic to non target organisms
-pesticides that are water soluble are more likely to be washed off crop, requiring re-application
what are contact pesticides
contact action:
-only protects surface of crop that are sprayed
-un sprayed surfaces aren’t protected
systematic action:
-absorbed by crop & translocated through crop
-protects all of plant
-can’t be washed off by rain & be eaten by humans
how can antibiotics be used in agriculture
-treat bacteria infections
-prevent infection
-promote growth
problems with using antibiotics in agriculture
-antibiotic resistance
-risk of zoonosis- inc some resistant bacteria are transferred to humans
how can pollinator services be aided
-provision of food supplies by growing plants that provide nectar
-restricting use of harmful pesticides
-introduction of bee hives
-companion crops
-habitat protection
how are nutrients supplied to soil?
-includes maintenance of soil biota, detritivores & decomposers
-nutrient supply in an abiotic factor controlled in agroecosystems
-nutrient supplies is a natural processes e.g. nitrogen fixing bacteria, decomposition & crop rotation
-nutrient supplies control productivity in different areas
what is soil biota
-all microorganisms, soil animals and plants living all/part of their lives in or on soil
-nitrogen fixing bacteria- convert nitrogen into nitrates
why is soil biota important
-inc nutrient supply via breakdown of DOM & nitrogen fixation
-organic acids produced by decomposition inc weathering of rocks & releases nutrients into soil
-earthworms inc aeration & drainage which aid aerobic process & water retention
