Section F: Crop production
Section F: Crop production
enter the water, adding
2) the extra nutrients cause
block out the light
plants can't photosynthesise
due to lack of light and
start to die
4) With more food available, microorganisms that feed on dead plants
increase in number
deplete all the oxygen
in the water
5) Organisms that need oxygen (e.g. fish) die
Pests include microorganisms, insects and mammals. pests that feed on crops are killed using various methods pest control
Pesticides are a form of
chemical pest control
. They're often poisonous to humans so the farmer must be careful to use a small amount. pesticides can also harm other wildlife
is an alternative to using pesticides. it means using other organisms to reduce the number of pests either by encouraging wild organisms or adding new ones
the helpful organisms could be
(e.g. ladybirds eat aphids),
(e.g. some flies lay there eggs on slugs which eventually kills them) or **disease-causing (e.g. bacteria against caterpillars.)
Biological control can have a longer-lasting effect than spraying pesticides, and be less harmful to wildlife. But introducing new organisms can cause problems - e.g. cane toads where introduced to Australia to eat beetles and are now a major pest
Glass Houses and polythene tunnels
In glasshouses and polythene tunnels conditions can be controlled.
This control means that all the limiting factors for plant growth can be set to the optimum conditions; (e.g. it can be set to the optimum temperature, humidity, light and CO2 concentration)
This will result in more growth, so higher yield.
Effects on crop yield
Glass houses and polythene tunnels increase the heat in the environment that crops are growing in.
Reactions happen faster when there is more heat, for example photosynthesis. Given photosynthesis produces energy that the plant needs to grow, if there is more heat there is more growth and so higher yield.
Carbon dioxide is a reactant in photosynthesis. If there is a more than enough carbon dioxide, then every plant will be able to photosynthesise as best as it can.
The more photosynthesis the more glucose, the more glucose the more energy, the more energy the more growth. Hence crop yield is increased.
minerals in plants
Different mineral ions do different things:
- contains nitrogen for making
. these are needed for cell growth. plants without this have stunted growth and yellow older leaves
- contain phosphorus for making
and needed for
. Plants without this have poor root growth and purple older leaves
to help enzymes needed for
. Plants without this have poor flowers and fruit and discoloured leaves
is needed for making chlorophyll(needed for photosynthesis). plants without this have yellow leaves
As well as water and sunlight, plants require mineral ions to grow.
farmers use fertilisers to replace missing minerals/elements to increase crop yield
Sometimes the elements that a plant needs are missing from he soil because they have been used up by previous plants