OCR A-Level Geography H481
Coastal Landscapes
Glaciated Landscapes
Dryland Landscapes
Earth’s Life Support Systems
Changing Spaces; Making Places
Trade in the Contemporary World
Global Migration
Human Rights
Power and Borders
Climate Change
Disease Dilemmas
Exploring Oceans
Future of Food
Hazardous Earth
Geographical Skills
Future of Food
Salinisation, deforestation and agrochemical pollution from farming
- 2 things to know
- Component 03
Overview
Recall questions on salinisation and waterlogging under irrigation, their effect on yields and extent, reclamation and salt-tolerant crops, cattle ranching, soy and oil palm as causes of deforestation, biodiversity loss and reduced rainfall, eutrophication and dead zones, nitrate in groundwater, pesticide bioaccumulation, pollinator decline, and changing farm landscapes.
What you need to know
Answer each one before you reveal it.
Define salinisation.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define salinisation.
Model answer
Salinisation is the accumulation of soluble salts in the upper soil to concentrations that damage crops.
- 2
Explain the mechanism by which irrigation causes salinisation in a hot, dry climate.
Model answer
Irrigation raises the water table, and dissolved salts are drawn upwards by capillary action, so as the water evaporates at the surface the salts are left behind and steadily concentrate.
- 3
Explain why high soil salinity reduces crop yields.
Model answer
Salts lower the osmotic potential of soil water so roots cannot draw it in, producing a physiological drought, and some of the ions are directly toxic to the plant.
- 4
What is waterlogging, and how is it linked to irrigation?
Model answer
Waterlogging is the saturation of the root zone, and it occurs when irrigation water is applied faster than the soil can drain, raising the water table towards the surface.
- 5
Roughly what share of the world's irrigated land is affected by salinity?
Model answer
About a fifth of it.
- 6
Give two ways salinised land can be reclaimed or protected.
Model answer
Installing drainage and flushing the soil with surplus water so that salts are leached away, and lining canals and switching to drip irrigation so less water reaches the water table.
Other ways to work this
The same content, four other ways.
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Six ways to work the same material.
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