Agricultural energetics Flashcards
how is the intensity of agriculture measured?
by how much inputs are fed into the system and the yield that is then produced
What are the two types of farming?
extensive farming
intensive farming
what is extensive farming?
maximise yields by spreading the inputs over a large are
what is an example of extensive farming?
typical of hill sheep where the soil isn’t good enough to have a lot of sheep in a small area
what is intensive farming?
where large inputs are placed onto relatively small pieces of land
include fertiliser, labour and energy
what are the advantages of intensive farming?
yield usually high
what are the limitations of intensive farming?
calculated yields per unit of inputs may not be very high
so productive but not always efficient
what links productivity and efficiency? (agriculture)
explained by the law of diminishing returns
what is the law of diminishing returns?
initially extra unit input (fertiliser or manpower) results in increased yield
size of each yield increase gets smaller over time
As there is only such much that can be added (nutrients, light) to a crop or animal before it cant grow any more
what does the law of diminishing returns mean for intensive farming?
is a limit to how efficient it is and productivity may improve if some areas that are intensively farmed as not farmed intensively
total global inputs should be spread over more areas
what is an energy subsidy?
any input that aids productivity but requires the use of energy
what are examples of agriculture energy subsidies?
manufacture nitrate fertilisers
manufacture pesticides
pumping irrigation water
fuel for machinery (Ploughing spraying harvesting)
energy to manufacture machinery and equipment
heat for drying harvested grain
processing food for consumers
transport food to consumers
what ways do farms subsidise their energy from fossil fuels?
will use fossil fuels for heating, lighting instead of natural sunlight and normal outside temperatures
CO2 will be pumped into crop farms as a part of photosynthesis
in the USA how much of the fossil fuel is spent on agriculture?
17%
what aspects of agriculture is especially fossil fuel intensive and why?
to power heavy farming machinery
process foods
refrigerate foods during transportation
production of packaging material
manufacture and transport chemical inputs (fertiliser)
why are energy ratios used? (Agriculture)
measure of efficiency by comparing energy inputs and outputs and then expressing them as the number of units of food energy produced per unit of energy input
What will the yield of area with higher energy ratio values?
higher yield per unit of energy
Is energy ratio the same as productivity per unit area?
no a system with high productivity may require high energy subsidies therefore have a low energy ratio
What does |FCR stand for?
Food conversion ratios
What are the typical intensive and extensive values of certain products?
Wheat= ex- 11 in-5
rice= ex-16 in- 4
beef= ex- 0.3 in- 0.1
milk= ex- 1.2 in- 0.4
what is the food conversion ratio a measure of?
mass of food needed to produce a given mass of livestock growth
what dies a low FCR mean?
better conversion of food into animal biomass
What is the FCR of some livestock?
Salmon (aquaculture)- 1.1
chicken- 1.7
pork- 3.1
sheep- 6
beef- 7
What do all living organisms need to drive biological metabolic processes?
Chemical energy
What must breakdown the chemicals to produce chemical energy? (Carbon cycle)
Autotrophs (self feeders)
Why are autotrophs important?
Without them chemical energy needed for biological metabolic processes wouldn’t be readily available in the environment
What do autotrophs need?
A source of energy to build up high energy molecules
What high energy molecules do autotrophs produce?
Carbohydrates-glucose, starch and cellulose
Lipids- fats and oils
What is the most common type of autotroph?
Photo autotrophs
What are the most common types of photo autotrophs?
Plants
Algae
Photosynthetic bacteria
How do photo autotrophs work?
They capture sunlight and use to to produce energy
What is the equation for photosynthesis?
6CO2+6H2O———-> C6H12O6+6O2
Light
What are chemo-autotrophs and how do they work?
Bacteria that harness energy by oxidising substances
What substances do chemo-autotrophs oxidise?
Hydrogen sulphide
Methane
Ions of ammonium and nitrate
What big advantage do autotrophs have for survival?
They don’t have to rely on other organisms for their energy supply
What do all other organisms rely upon for their energy supplies?
Autotrophs
What must organisms that cannot produce their own high energy molecules do?
Must gain their energy from other living organisms
What are Heterotrophs?
Organisms that get their high energy molecules form other organisms
What are some examples of heterotrophs?
Animals
Fungi
Many bacteria
What problems do heterotrophs have with getting energy?
Metabolic processes release some energy back into the environment as low-density heat meaning less energy is available further down the food chain
Why do food chains/ pyramids only have four trophic levels?
As a in food chain with several trophic levels, less energy is passed to the next trophic level
What is a trophic level?
The level/ position an organism occupies in a food chain
What is a primary producer?
Autotrophs capable of producing organic compounds from light energy or chemical energy
Vegetation
Photosynthesis
First trophic level most energy
What are primary consumers?
Herbivores
Second trophic level
Eat primary producers and nothing else
Grasshopper eating grass
What is a secondary consumer?
Third trophic level
Carnivores
Eat primary consumers
Tend to be larger and fewer in number
Fox eating a rabbit
What are tertiary consumers?
Those that eat secondary consumers
Large predators
Owls that eat snakes
4th trophic level
