agriculture Flashcards
(33 cards)
Explain why intensive agricultural systems have higher energy inputs (3 marks)
- Use of fertilisers
- requires irrigation
-manufacturing/use of machinery - control of abiotic factors eg use of artificial lighting
Explain how factors that limit productivity may be managed to increase the sustainability of crop production (6 marks)
- Insects can be controlled using biological control or insecticides.
- low nutrient availability can be controlled through organic manures/nitrogen fixing bacteria
- crop rotation
- drip irrigation
- multi-cropping
The food samples collected were individually wrapped before being sent for analysis of pesticide levels. Why is this less important for samples containing systemic pesticides than contact pesticides? (1 mark)
Systemic pesticides will be retained within the food.
Suggest why pesticide residue levels in samples of a single type of food may show high variability (4 marks)
- types of pest may vary
- seasonal changes/species life
cycles affect abundance
(requiring different application
rates) - different methods/timing of
application affect
concentrations
Variation after application - rainfall
- time before harvest
- increase in mass causes
dilution - storage/treatment method
Describe three advantages of using pyrethroids (3 marks)
- does not remain in the
environment for a long period
of time/low persistence - (as it) degrades quickly
- not liposoluble/do not
bioaccumulate/ biomagnify - high specificity/high insect
toxicity/low mammal toxicity
/fewer non-target species are
killed - insoluble in water/low mobility
- not carcinogenic
Describe three indirect affects of pesticides on living organisms (3 marks)
1) loss of potential food source
2) loss of an ecosystem service eg seed dispersal or pollination.
3) Some species become more abundant as predators have been removed.
Barrier crop
Crop rotation
eg Lupin plants hosting nitrogen-fixing bacteria are cultivated to
improve soil fertility
Genetic modification
eg Plasmid containing DNA code for antifreeze protein inserted into
young strawberry plants
Introduced pathogen
Introduced predator
Leguminous crop
eg Introduction of Phytoseiulus persimilis mite that feeds upon
Two-spotted Spider Mites, Tetranychus urticae, which would
reduce strawberry crop yields
Mulching
the practice of covering the soil surface with a layer of material, typically organic matter, to protect plants and improve soil health.
Pheromone traps
They work by using synthetic sex pheromones (or attractants) to lure male moths (or both male and female beetles) into traps. This allows farmers to monitor pest populations, determine the timing of treatments, and even reduce pest numbers
Weeding
Explain why neonicotinoids are less likely to build up in soil than in aquifers (3 marks)
Any three from:
* More suitable conditions for
decomposers/bacteria
* Suitable temperature: rate
of decomposer activity,
kinetic energy for chemical
reactions
* No light for
photodegradation
* Less water
* Lower mobility/dispersal
Suggest possible causes, other than the use of neonicotinoids, of the decline in the bee population. (3 marks)
- Changed farming practice
- Other pesticide
- Weather/climate change
- Change in inter-dependent
species
Explain how the total amount of pesticide used may be reduced by using seed
coatings of persistent systemic pesticides rather than aerial spraying of nonpersistent contact pesticides. (3 marks)
Any three features that reduce the
amount used, from:
* Accurate positioning (on
seed) (because seed coating
rather than aerial)
* Translocation throughout
plant (because systemic
rather than contact)
* Longer presence (because
persistent)
* Reduced need for reapplication (because
persistent/systemic)
* No spray drift (because seed
coating rather than aerial)
Plagioclimax
Habitat where human activity has prevented the ecosystem from developing
Define the term ‘vegetative propagation’. (1 mark)
Production of genetically identical offspring/asexual reproduction
Explain how transferring the potato plants to the field as a monoculture may affect the yield. [2 marks]
- all plants have same pests
- specific pesticides make pest control easier, increasing yield
or - increased risk of pest infestation, greater risk of yield loss
OR - all plants have same disease resistance
- specific pesticides make disease control easier, increasing yield
or - increased risk of disease, greater risk of yield loss
OR - all plants have the same nutrient needs
- specific fertilisers may be used to increase yields
or - increased competition for the same nutrients/ reduction in soil
fertility may reduce yields
Explain how one method of gene manipulation is used to increase crop yields. [2 marks]
- genetic modification/transgenics/ gene editing/ selective breeding (or
description of method) - named trait (to increase yield) e.g. pest resistance, drought
resistance, frost resistance, salinity tolerance
Explain why systemic pesticides do not impact non-target species that land on crops.
[1 mark]
- Pesticide inside plant tissue
Explain how the use of pesticides can reduce the availability of soil nutrients. [4 marks]
- death of detritivores/decomposers
- reduces breakdown of organic matter
- death of nitrogen fixing/nitrifying bacteria
- reduces nitrate availability [A ammonium]
- death of burrowing organisms/worms
- reduces oxygen for decomposition/ nitrogen fixation/nitrification
- reduces drainage increasing denitrification
- death of mycorrhizal organisms
- reduces nutrient uptake.
What is hydroponics?
The growth of crops in a nutrient solution rather than a solid growth medium
