Energy and Food Production

Mr Lee19-11-2013

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Agricultural ecosystemsRyegrass –Lolium perenne

Cow-Bos primigenius

Human –Homo sapiens

Ryegrass –Lolium perenne

Cow-Bos primigenius

Agricultural food chain

Very few trophic levels means greater efficiency

Agricultural ecosystemsHigh net productivity

net productivity

= gross productivity

- respiratory losses

Unit of productivity = kJ m-2 year-1

Natural ecosystems

Agricultural ecosystem

Solar energy only – no additional energy input

Solar energy plus energy from food (labour) and fossil fuels (machinery

and transport)Lower productivity Higher productivity

More species diversity Less species diversityMore genetic diversity within a

species Less genetic diversity within a species

Nutrients are recycled naturally within the ecosystem with little addition

from outside

Natural recycling is more limited and supplemented by the addition of

artificial fertilisersPopulations are controlled by natural

means, such as competition and climate

Populations are controlled by both natural means and by the use of

pesticide and cultivation

Is a natural climax community Is an artificial community prevented from reaching its natural climax

What factors affect productivity?

CO2 levels

Humidity

Light intensity

Temperature

How do we control these?

Atmospheric CO2 is roughly 0.04%

Increasing to 0.1% has been shown to improve tomato crop yields by up to 20%

Pest control

Aphid Pseudococcidae (Mealybug)

Pesticides- Chemicals that kill pests

Herbicides- kill plants

Fungicides - kill fungi

Insecticides- kill insects

Be specific: so that it is only toxic to the organisms at which it is directed. It should be harmless to humans and other organisms, especially the natural predators of the pest, to earthworms, and to pollinating insects such as bees

Biodegrade: so that once applied, it will break down into harmless substances in the soil. At the same time, it needs to be chemically stable, so that it has a long shelf life

Be cost effective: because development costs are high and new pesticides remain useful for only a limited time. This is because pests can develop genetic resistance (due to mutations), making the pesticide useless

Not accumulate: so that it does not build up, either in specific parts of an organism or as it passes along food chains

Pesticides should……………

Biological Pest controlUsing other organisms to control pests e.g.

Discuss possible pros and cons of each type of pest control

BiologicalPros Cons

Cheaper than chemicals Not as quick actingNot harmful to the environment Control organism could become a pestDoes not require re-application Does not totally eradicate pestVery specific  

ChemicalPros Cons

Fast acting Can accumulate in the environmentCan eradicate a population of pests Can affect non target speciesCan control exactly where it is Expensive and needs re-applying  Pests can develop genetic resistance

Other methods………Intercropping- providing habitat for predator

species in amongst the main crop.

Crop rotation- different crops each year; new crop is unsuitable for last years pests

Physical barriers- covering plants e.g. tubes on tree sapling prevent deer and rabbit browsing

Mulching- prevents light from reaching weeds

Intensive farming

Intensive farming

Intensive farmingMovement is restricted and so less energy is

used in muscle contractionThe environment can be kept warm in order

to reduce heat loss from the body (most intensively reared species are warm-blooded)

Feeding can be controlled so that the animals receive the optimum amount and type of food for maximum growth with no wastage

Predators are excluded so that there is no loss to other organisms in the food web

Is it all bad?Split in to two groups

One side is pro intensive farming?

One side is anti intensive farming?

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