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In agriculture, radiation is used to improve food production and packaging.

The radioactive source, phosphorus-32, is used to study the uptake of fertilisers by plants.

It is mixed with fertiliser and fed to plants through the soil.

Phosphorus-32 emits beta particles and has a half-life of 14 days.

By measuring the radiation given out by the leaves, a researcher can find out how much fertiliser has reached them.

This information can be used to make grass and cow farming more productive.

Food preservation

Gamma radiation from a radioactive source such as cobalt-60 can be used to kill bacteria on fresh food and enable it to keep for longer.

Harmful bacteria, moulds and yeasts grow on foods, and can be killed by gamma rays.

This helps to prolong the shelf life of fresh fruit, vegetables, spices, fish and chicken, reduces food poisoning and food waste, and helps to keep prices down.

Using radiation in this way does not make the food radioactive as the food itself never comes into contact with the radioactive source.

It is the energy from the radioactive source in the form of gamma rays that kills the bacteria that can cause food poisoning in a similar way that heat energy kills bacteria when food is heated.

Once the radiation treatment has stopped, the food quickly loses this energy in the same way that cooked food quickly cools down.

Other uses of radiation in agriculture include:

• Plant seeds can be exposed to radiation to produce new, stronger and better plants.
• Radiation can be used to control the number of dangerous insects. This decreases the use of dangerous pesticides.
• Radioactive sources are used in machines that measure the thickness of eggshells to screen out thin, breakable eggs before they are packaged in egg cartons.
• Many of our foods are packaged in polyethylene shrinkwrap. This is exposed to radiation so that it can be heated above its usual melting point and wrapped around foods to provide an airtight protective covering.