Tree Care-Managing Salt Burn
Excerpt from February 2011 Tree Tips Newsletter
In last months newsletter I mentioned the negative effects that salt accumulation has on both the soil and plant tissue. It is such a common problem with a simple solution that I thought it deserves a more detailed discussion.
It is not uncommon in locations of low precipitation or inadequate drainage to have a soil salt accumulation problem. This is due to the fact that there is not enough deep penetration of water in the soil strata to move the salt below the root system. Because salt is soluble the best way to resolve the issue is periodic deep irrigations. This has two benefits: first it removes the salt from the root zone and secondly, with a monthly deep watering, it encourages the roots to penetrate deeper which in turn leads to more root volume. A more extensive root system can deliver more water, more nutrient and better plant stability.
One of the most common problems I encounter in my work is with trees grown in lawn areas or flower beds with annuals and perennials. Because lawns and flower beds require more frequent and shallow waterings the land owner assumes that this will be adequate for the trees in the immediate area. Unfortunately what results is that the tree roots over time come to the surface which causes many problems such as exposure to radical and frequent changes in the soil temperature, soil moisture, soil pH and fertility and a smaller root system that fails to provide strength and stability.
The other major concern is the build up of salt in plant tissue. The simple explantion of tissue damage due to salt burn is that when a high concentration of salt is on one side of a membrane and a low concentration is on the other side of the membrane the natural response is to equalize the per cent of concentration on both sides. So what happens is that pure water will move out of a cell to dilute the concentrated solution outside of the cell. And in doing so you dessicate the cell which is a nice word for killing the cell. This is usually first noticed on the leaf tips and margins.
This is logical if you think about it. As the water saturated with salt moves to the extremities of the plant and the water is either utilized by the plant or transpired off the salt concentration becomes greater and greater until you have complete dessication.
As I mentioned last month the most common sources of salt are either the parent material of your soil or your irrigation water. You should also be aware that all synthetic fertilizers are formulated as a salt because of their solubility. Thats why a salt burn and a fertilizer burn look the same-they are the same.
So the whole point of this discussion is to get you to deep water at least once a month during the growing season. If you do this one thing your trees will be so much healthier and happier in a year.
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