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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.

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Process

Explain the mechanism by which irrigation causes salinisation in a hot, dry climate.

Key term

Define salinisation.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define salinisation.

    Model answer

    Salinisation is the accumulation of soluble salts in the upper soil to concentrations that damage crops.

  2. 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. 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. 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. 5

    Roughly what share of the world's irrigated land is affected by salinity?

    Model answer

    About a fifth of it.

  6. 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.

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