why can’t we use salt water for irrigation?
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It would need to be desalinated first which is not easy to do. Otherwise it would destroy the crops and land.
For plants? Because plants can’t take the salt concentration
And to desalinate? There currently isn’t a way to desalinate saltwater that is economical and mechanically achievable on the scale that would be needed. Salt is also hard on mechanical parts. It is doable with the right amount of money….which is a lot.
Essentially every plant that grows in the ground requires fresh water rather than salt water. Absent human intervention, they would get water from just rain, which is fresh water, so they have evolved to expect that. Give them too much salt in their water, and they will shrivel up and die, just like you.
Too much salt will make the earth no good for growing crops. There’s a saying that one “salts the earth” when talking about making ground unusable for agriculture.
Salt is toxic to most terrestrial plants. This fact has been used in the past to “salt the Earth” and prevent conquered peoples from growing crops. Since seawater is very salty, it would kill most crops.
when you water plants, the water gets pulled up through littles holes in the roots and then has to enter the plant’s cells. osmosis tells us that water wants to go from a less salty place to a more salty place. fresh water is less salty than the insides of plant cells, so it will give water to the cells and plump them up. salt water is saltier than the plant cells, so it goes backwards: the cells give up their water and shrivel up.
Salt water can be used for irrigation, but it is not as effective as fresh water because it can cause salt build-up in the soil, which can damage plants.
You know when you eat something very salty, you get thirsty? The same thing happens to the roots of a plant, except that is their only way of getting water, so they die.
The answers so far have not explained why salt is bad for plants. Too much salt makes it impossible for plant roots to absorb water.
Water has a tendency to move from areas with low concentrations of dissolved stuff or solute (such as salt, sugars and other molecules), to areas of high solute concentration. Plants normally take advantage of this to absorb water from the soil. The root cells have higher solute concentrations than the surrounding soil. The membrane around the cell lets water pass through but controlls how much salt passes through. This means water moves from the surrounding soil into the roots. If you irrigate with salt water, the water in the soil will eventually have a higher solute concentration than the plant roots can maintain and water will tend to move out of the plant.
Some plants have adaptations that let them keep higher solute concentrations in their roots, so they can absorb water from salty soil.
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