The precise role of sodium in plant health is unclear at the present time. However, some scientists believe that sodium may be needed for carbohydrate metabolism in at least some species of plants. Also, it is possible that sodium can substitute for potassium in regulating the opening and closing of the stomata, which would mean that it is important in regulating water balance.
Sodium may also improve the flavor of the crop when taken up by the plant.
Sodium is found in most water sources, particularly during periods of dry weather.
Some gardeners use salt, particularly sea salt, as a fertilizer.
Most experts state that plants do not need sodium and that they therefore cannot suffer from sodium deficiency.
However, some plants appear to respond well to being fertilized with salt, particularly those that were originally seashore plants. Studies on sugar beets showed that fertilization with sodium increased sugar levels. Likewise, salting the asparagus bed was a common way to fertilize the plants and keep the weeds in check in the 1800s.
Keep in mind that, in the case of sea salt fertilizers, any benefits reaped may not be due to the sodium, but related to the many other minerals that sea salt contains.
Sodium is extremely toxic to plants. It can accumulate in the soil at dangerous levels during prolonged dry spells. It can also become a problem if salty water is used in the garden or if too much fertilizer (particularly sea salt fertilizer) is applied over time.
Symptoms of sodium toxicity in plants include:
- Stunted growth.
- Scorching of leaf tips and margins.
- Reduced yield.
The good news is that excess sodium is fairly easy to flush out of the soil with ample water (uncontaminated water, of course). Afterward, you will need to replace any other water-soluble minerals you might have washed away, as well.