Soluble Salts

Definition - What does Soluble Salts mean?

Soluble salts are the sodium-based trace elements present in soil and other types of grow media that are able to dissolve in water. Soluble salts change their composition as they dissolve into a form more easily absorbed by plants.

MaximumYield explains Soluble Salts

When an ionic crystal such as salt or sugar is placed in water, a dissolving reaction tends to occur. Initially, the positive and negative ions of the crystal are only attracted to each other. The molecules of the crystal that are made of hydrogen are bonded to each other. If the crystal is to dissolve, these hydrogen bonds must be broken.

In the dissolving process, the positive sodium ions are attracted by both the chloride ions and the partially negative oxygen atoms in the water molecules. Whether a salt crystal dissolves or not is determined by which attractive force is stronger. When the internal ionic forces in the crystal are strongest, a crystal will not dissolve. If the attractions for the ions by the water molecules are the strongest, then the crystal will dissolve.

The excessive presence of soluble salts in a grow medium can be a limiting factor in the production of greenhouse crops. Soluble salt accumulations often result from the use of poor-quality irrigation water, overfertilization, or growing in a medium with a naturally high salt content. Although soluble salts may inhibit plant growth, these effects can be controlled through proper monitoring of the greenhouse.

Soluble salts in irrigation water are measured using electrical conductivity (EC). The higher the salt content, the greater the EC will be. In general, EC values exceeding 2.0 are considered harmful for plants.

Water quality should be monitored on a regular basis in order to avoid any potential problems from soluble salts.

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