Agriculture not completed Flashcards
Why is temperature important and how can it be controlled?
- Must be warm enough for growth.
- Frost can damage a crop.
- Energy goes into keeping warm so keeping a warm temp helps.
- Greenhouses.
- Provide shelter/building that are heated/ventilated for livestock.
Why is light important and how can it be controlled?
- High light intensity = increased photosynthesis.
- Photoperiodism affects growth of plant.
- Poultry grow well with short daylengths.
- Artificial lighting.
Why is water important and how can it be controlled?
Physiological functions.
- Nutrient absorption.
- Cell water produces cell turgidity = provides support.
- Transport materials.
- Needed to replace water loss from transpiration.
- Waterlogged soils increase risk of fungal disease + soil becomes anaerobic.
- Reduce –> drainage, ditches, ploughing.
- Increase –> Irrigation, soil mulching, reduce soil compaction for increased filtration, adding soil organic matter to increase water retention.
Why is aeration important and how can it be controlled?
- Many soil processes aerobic (i.e. nitrogen fixation).
- Soil compaction caused by livestock, heavy machinery kills soil organisms.
- Ploughing aerates soil.
- Adding organic matter as food.
- Removing livestock from wet fields.
Why is soil salinity important and how can it be controlled?
- Dissolved salts essential for plant growth but too much causes osmotic dehydration.
- Avoid irrigation using salty groundwater.
Why is soil pH important and how can it be controlled?
- Range of tolerance usually pH5-7.
- Low pH can increase leaching of nutrients.
- High pH inhibits nutrient solubility.
- Increase = crushed lime
- Decrease = powdered sulfur.
Why is carbon dioxide important and how can it be controlled?
- Limiting factor of photosynthesis.
- Burning carbon based fuels.
- Paraffin heaters.
Why is topography important?
- Valleys produce areas more exposed to sunlight.
- Cold dense air collects in low-lying areas (frost = death).
- Steeper gradients = increased surface runoff and soil erosion.
What are the advantages and disadvantages of organic fertiliser?
+ Release nutrients gradually = last ages.
+ Cheap to manufacture.
+ Increase humus content = reduces soil erosion.
+ Food for soil biota.
- Does not provide large amounts of nutrients quickly.
- Difficult to transport.
- Can’t be applied when a crop is actually growing in a field.
- Can’t control nutrient dosage.
What are the advantages and disadvantages of inorganic fertilisers?
+ Can control nutrient content.
+ Available to crop instantly.
+ Easy to apply mechanically.
- Does not add humus to soil for soil biota.
- Can be toxic for soil biota.
- Expensive to manufacture, requires lots of energy.
- Can be easily leached.
What are systemic pesticides?
Absorbed by the crop and transported through whole plant.
+ Won’t wash off.
- Can’t wash it off if inside plant.
What are contact pesticides?
Sprayed on a plant.
- Can kill plants by damaging tissue, and can also kill insects that come in contact.
- Can be washed off, plant becomes unprotected.
What are organochlorines?
They are BANNED.
They are highly toxic to insects, have a high persistence and liposolubility (not washed off easily).
- Kills non-target species (bees).
- Bioaccumulation and biomagnifies up food chain.
- Remains in environment for decades.
What are organophosphates?
They are BANNED.
Low persistence and liposolubility - do not bioaccumulate and biomagnify.
- High mammalian toxicity (is a neurotoxin and damages nerves).
- Chronic exposure leads to depression, impaired memory, ADHD, alzheimers etc.
What are pyrethoids?
High insect toxicity, low mammal toxicity, not persistent, don’t bioaccumulate or biomagnify.
- Safe unless large dosages absorbed.
- Toxic to fish so no using near rivers.
