What is agriculture?
• Agriculture refers to the
purposeful raising of crops
and livestock by man to
produce useful commodities
e.g. foodstuff and fibres.
Food &
Raw materials
PHYSICAL
INPUTS
CULTURAL
INPUTS
PROCESSES
OUTPUTS
CASH
MARKET
MANURE
SEED
FARM
HOUSEHOLD
Type of farming
• Arable farming
• Pastoral farming
• Mixed farming
•Crop only(cash /cereal)
•livestock
•crop & livestock
• Subsistence farming
outputs are for own consumption
• Commercial farming
outputs are for sale in market
• Labour extensive
farming
• Capital extensive
farming
• Labour intensive
farming
• Capital intensive
farming
• Low man-land
ratio
• low capital-land
ratio
• high man-land
ratio
• high capitalland ratio
Farm A
Farm B
Farm Size
1 hectare 200 hectares
No. of farmer
5 persons
5 persons
$200
$100,000
Man-land ratio
Total cost for
machinery,
fertilizers & etc.
Capital-land ratio
Agroecosystem
An agricultural ecosystem
Farm as an ecological system
• An ecosystem is a functioning and
interacting system of living
organisms and its effective
environment(including biotic and
abiotic)
• Human manipulated ecosystem
R
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p
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a
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Producers
Primary
Consumers
Energy
flow
S.
C.
Nutrient
cycle
D
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p
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Energy Flow
• Energy flow is the transfer of energy through
various living organisms along the food chain.
• Plants absorb solar energy and produce organic
food by photosynthesis.
• Part of the energy in food is used by plants
themselves during respiration.
• Another part of the energy is stored in the
plants and then passed on to the primary
consumers when they eat the plants.
• When the primary consumer is eaten, energy is
passed on to the secondary consumers in the
same way.
• At each trophic level, a large part of energy is
used up in the organisms’ respiration and
metabolic activities.
• Respiration produces heat energy which is lost.
This is called heat loss.
• That is to say, as each higher trophic level is
reached, there is an accumulated loss in energy.
• Hence there is usually a large number of first
order consumers, fewer secondary order
consumers and still fewer third order consumers
further along the food chain. Such continuous
loss of energy can be shown by a production
pyramid.
Nutrient Cycling
• Inorganic nutrients are taken up by plants to make
organic matter during photosynthesis.
• The nutrients are then passed form one living
organism to another along the food chain.
• When the living organisms die, their dead bodies are
decomposed by bacteria and fungi.
• through decomposition, the organic matter is
converted back into simple inorganic substances
such as water and carbon dioxide
• All the nutrients are then returned to the
atmosphere, lithosphere or hydrosphere.
• When these nutrients are taken up by plants again,
new nutrient cycles start.
A Rice farm in South China as
an agroecosystem
Producers
Padi(rice), weeds,
vegetables, field crops
Consumers
Human beings,
animals(pigs/poultry),
pests
Decomposers Bacteria, fungi
Sub-tropic climate
Atmospheric abundant sunlight, 20oC,
1200-3000 mm annual rainfall
river valleys, deltas, flood
Lithospheric plain (alluvial soil)
terraces on hilly land
subsidized energy in terms of
Human
irrigation, machines, fertilizers or
environment
manure
R
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p
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a
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Producers
Primary
Consumers
Energy
flow
S.
C.
Nutrient
cycle
D
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p
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Energy flow
• Active photosynthesis
• high primary productivity(double/triple
cropping)
• energy subsidies are used(fertilizers,
irrigation, transplanting, machinery)
• man as the major consumer
• herbicides and pesticides are used to
minimize weeds and pest(competitors)
Nutrient cycling
• Alluvial soil is rich in nutrients(humus)
• rapid uptaking / large amount
• harvest removes nutrients from
system(especially for commercial farm)
• natural nutrient cycling is incomplete
• manure/ chemical fertilizers is needed
Role of man
Natural
ecosystem
Agroecosystem
insinificant
ecological dominant
Both natural &
Natural inputs
Inputs
human inputs
No human input
Energy subsidies
shorter food chain
Energy flow Longer food chain
human directed
more trophic levels
flow
natural cycling of Modified nutrientNutrient
nutrients
cycle
cycling
closed system
Open system
Natural
ecosystem
Agroecosystem
Biomass
Small seasonal
variation
Great seasonal
variation,
amount depends
Diversity
of
organisms
Greater
Natural habitat
More species
Very low
Man-made habitat
More complicated
More stable
Simple structure
Less stable
Stability
Energy efficiency
Total energy produced
Energy ratio 
Total cultural energy energy input
Er=1
Er>1
Er<1
Farming System
• Pre-industrial
crops
• Semi-industrial
crops
• Full-industrial
crops
• Full-industrial
livestock
• Shifting
cultivation
• Subsistence paddy
farming
• Commercial wheat
farming
• Dairy farming in
Australia
Difference in Energy Efficiency
• Shifting cultivation has a higher energy
efficiency than plantation.
• Because of high rainfall and
temperature (physical inputs) and
sudden release of nutrient by the
burning of rain forest
• Plantations use large amount of energy
subsidies (machinery and chemicals).
Difference in Energy Efficiency
• There will be energy and nutrient loss
when they apply farming chemicals.
• Due to the carrying capacity of land,
there will be the effect of diminishing
return in the application of farming
chemicals.
Difference between crops and
livestock in Energy Efficiency
• Both commercial crops and livestock
farming involve large amount energy
subsidies
• However, the food chain of livestock is
longer (one higher trophic level)
• The longer is the energy flow, then the
greater energy loss will be
Difference between crops and
livestock in Energy Efficiency
• Only one tenth can be passed to a
higher trophic leve
• There is high loss of energy in
conversion from plant carbohydrate to
animal protein
Farm as an Economic System
Whether the inputs of
capital and labour can
result in financial gain?
Farmer as a
decision-maker
Questions for a farmer
• What to produce? •
• How to produce?
/Which production •
method?
• How much to
•
produce?
• How much to invest?
• How much to save
and borrow?
What to hire or
lease?
Where and how to
buy?
Where and how to
sell?
Market gardening in Hong Kong
works as an economic system
What to
produce?
Vegetables, flowers, poultry
How to
produce?
continuous cropping throughout the year,
6-8 crops of vegetable
irrigation is necessary in the dry winter
the size of farm is small
farming is very labour-intensive
terracing is practiced on hill slopes
application of fertilizers and pesticides
is necessary
most farm are operated on family basis
small hand machines are used
Where
and how
to sell?
produce meets the demand of local
market only
vegetables harvested are sent to
collection stations of the cooperative
bulk products of the cooperative are then
sent to the VMO (Vegetable Marketing
Organization) at Cheung Sha Wan
VMO sells the vegetables to retailers
some farmers by-pass the VMO and sell
their vegetables directly to customers in
market
part of the income received is reinvested to the farm for next harvest
Decision of farming method
-Mixed farming in Australia
Selection of crops and/or livestock
Ecological consideration
Economic consideration
Physical / ecological
conditions are suitable for
both wheat and sheep
Well-drained loam soils in
Murray-Darling Basins avoid
foot rot diseases and are
fertile enough for pasture
and wheat growth.
Mixed farming is less risky
and ensures a more stable
income
The two activities are
complementary. Labour
and farm equipment can be
fully utilized because
major work periods occur
at different time.
Ecological consideration
Economic consideration
The two activities are
supplementary. Wheat
provides stubble grazing
for sheep. Sheep waste
provides manure for wheat
lands.
Mixed farming helps keep
soil fertility and prevent
soil erosion. Crop rotation
and dry farming methods
are carried out.
Mixed farming enables a
more efficient use of
farmland. level and
fertile lands can be used
for wheat cultivation;
Area with steeper slope
and poorer soils can be
used for sheep rearing.
So the cost of production
of mixed farming is lower.