Crop farming

Describe how glasshouses and polythene tunnels increase crop yield - LIGHT

Describe how glasshouses and polythene tunnels increase crop yield - LIGHT

• transparent cover allows light through, creating a greenhouse effect.

• trapped heat energy raises temperature for soil and plants.

Describe how glasshouses and polythene tunnels increase crop yield - WATER SUPPLY AND HUMIDITY CONTROL

• too much or too little water reduces plant growth.

• humidity mustn't get too high - disease spreads caused by fungi and bacteria.

Describe how glasshouses and polythene tunnels increase crop yield - WIND

• temperature doesn’t fall as drastically.

• water loss caused by transpiration from growing plants is reduced.

• prevents damage to crops caused by strong winds.

Describe how glasshouses and polythene tunnels increase crop yield - FROST

• ice crystals formed in frozen cells cause them to burst.

• therefore, protects sensitive crops.

Why must carbon dioxide levels be monitored in a glasshouse/polythene tunnel?

• shortage limits photosynthesis.

• adequate ventilation means flowing air can replace carbon dioxide.

crop yield with increased carbon dioxide

• yield increases.

• increased rate of photosynthesis = plants grow faster

crop yield with increased temperature

• raised temperature increases enzyme reactions (including photosynthesis).

• therefore, plants grow faster and crop yield increases.

contents of chemical fertiliser

• Nitrates - makes amino acids.

• Phosphates - makes call membranes and DNA

• Potassium - makes ATP and drives enzyme reactions

examples of organic fertilisers

compost and manure

why is pest control important?

damage to crops reduces yield

chemical pesticides

toxic chemicals that kill the pest

biological control

by introducing a predator in the surroundings, the pest population decreases.

Advantages to chemical pesticides

1. work quickly and destroy the pest

Disadvantages to chemical pesticides

1. may kill a wide variety of organisms, not just the pest.

2. chemical substances in the pesticide break down quickly. crops have to be re-sprayed.

3. some pesticides stay in the soil and other organisms. Pesticides accumulate to levels toxic to larger organisms, and humans.

4. pests can evolve to become resistant to the pesticide

5. pesticides leached from soil and contaminate water sources.

Advantages to biological controls in crop production

1. biological control organisms only control specific species.

2. No polluting effects.

Disadvantages to biological control in crop production

1. if predator completely eliminates prey, predator has removed its won food supply, and will to eating non-target prey.

2. predator needs time to establish themselves in a new environment.

3. won’t completely eradicate pest.