why can't sea water be used for irrigation purpose?
Answers
So,the reason watering plants with seawater causes them to wilt (draws water out of the plant) is because the seawater has a lower water concentration than the plant. ....so,water can easily flow in and out of the cells, but not dissolved the salts.
Your question in itself states the fact that you KNOW that it cannot be done. So, I proceed to answer the "Why".
I really think that you should be knowing this..........and why you ask is a mystery. However, you have asked.......so, here goes......
First, sea water has very high saline content. that is not good for the plants that we normally like to grow, on land.
Next - The ideal pH for water for irrigation is 5.5 to 7.0, whereas the pH in case of sea water ranges from 7.5 to 8.4. This makes it highly acidic, for a normal crop.
Third, the density of the sea water ranges from about 1020 to 1029 kg/m3. This is because of salinity as well as other solubles. And this makes it rather tough for the plants on land to absorb the water.
However, you can treat the sea water and reduce the pH and the density and the salinity. But then the cost of this treatment will become so high that its cheaper to buy the farm produce using this money.