Ryegrass –Lolium perenne Cow-Bos primigenius Agricultural food chain Very few trophic levels means greater efficiency
Agricultural ecosystems High 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 productivityHigher productivity More species diversityLess species diversity More 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 fertilisers Populations 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%
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 control Using other organisms to control pests e.g.
Discuss possible pros and cons of each type of pest control Biological ProsCons Cheaper than chemicalsNot as quick acting Not harmful to the environmentControl organism could become a pest Does not require re-applicationDoes not totally eradicate pest Very specific Chemical ProsCons Fast actingCan accumulate in the environment Can eradicate a population of pestsCan affect non target species Can control exactly where it isExpensive 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
Movement is restricted and so less energy is used in muscle contraction The 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? !!!!!!!! IGNORE YOUR PERSONAL VIEW !!!!!!!! YOU ARE DEBATING