Salinisation Of Soils

Question 1

What is salinisation ?

Answer 1

Refers to the build up of salts in the soil eventually to toxic levels.

3,000-6,000 ppm causes trouble for most cultivated plants

Question 2

Why is salt in soils bad for plants ?

Answer 2

Decreases osmotic potential of soil
Soil has greater concentrations of solute than the root.
So plants can’t get water from soil.

Decreases yields

Question 3

How does salinisation occur ?

Answer 3

Excessive water application ( not too little)
All irrigation water contains dissolved salts derived as its passed over lands.
Evaporation.

Or when groundwater is within 3 metres or less of surface.

Question 4

What does rainwater contain ?

Answer 4

Some salts.

Evaporation of this water from dry surface soil leaves salts behind.

Question 5

What happens when groundwater is working 3 metres or less of surface ?

Answer 5

Water rises to surface by capillary action rather than percolating down through entire soil

It then evaporates from soil surface leaving salts behind

Question 6

How much farm land are affected by salinisation ?

Answer 6

10-20%

Hot semi arid areas which are poorly drained and use a lot irrigation water.
With not enough sufficient rainwater to flush salt out of soil.

Question 7

Where does salinisation occur . Give location

Answer 7

China’s northern play.
Central Asia
Indus plain of Pakistan

Worse for poor areas as crops are large form of food and income.

Question 8

Treatment for salinisation ?

Answer 8

Flush soil with lost of water.

But this leads to salinisation of groundwater and rivers.

Question 9

Example of where salinisation has occurred ?

Answer 9

Flushing of soil in the lower Colorado river valley.
River became Too salty down stream for Mexican farmers to use for irrigation.
They had to get desalinisation plant

Question 10

Extreme cases of salinisation

Answer 10

Salt crust too think to be flushed.

As water just runs off salty surface.