Learning outcomes:

describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops
understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses
understand the use of fertiliser to increase crop yield
understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants - b
Greenhouses and polythene tunnels raise the temperature (by the greenhouse effect… guess why it’s called that), which increases the rate of photosynthesis, which increases crop yield.

Yield - The total mass of the edible part of crop
If the level of CO2 in the greenhouse is increased the yield will further increase (remember, CO2 is a limiting factor in p/s)

If fertilisers are added (specifically those that contain Potassium, Nitrate and Phosphate– NPK fertilisers) then the yield will increase even more!

Potassium – essential for plant membranes
Nitrate – essential for making plant proteins
Phosphate – essential for DNA and membranes

Pest Control can also be used to increase Yield. This can be done either using pesticides or biological controls.

Pesticide – a chemical that kills pests (anything that eats your crop), but does not harm the crop plant
Biological control – introducing a biological organism which will eat the pest, but not the crop plant (e.g. birds are sometimes encouraged inside greenhouses because they eat caterpillars)