Some soils, like some humans, might need a low-salt diet. The Soil Science Society of America (SSSA) Soils Matter blog explains where salt in soil comes from and what can be done about it.
“For humans, we think of salt as table salt (a.k.a. sodium chloride), but salts are made up of many more compounds than just those,” writes Meagan Hynes, a certified professional soil scientist. “You can have salts made up of calcium, magnesium, or potassium that are paired with chloride or other ions like sulfate.”
Where Does Salt in the Soil Come From?
Well, soil comes from rocks and organic materials (e.g. decomposed plants). As these materials form soils through weathering, they will create “salts” found in the soil. The soil can replenish its salt content by these natural processes over long periods of time.
Other salts occur naturally in the soil, and are slowly replenished. In urban settings, recycled irrigation water may contain higher salt levels. Salt spread on roads and sidewalks to deal with icy conditions also contribute to levels in the soil.
In urban areas with gardens and lawns, we typically have plants that were not adapted to this slower nutrient “resupply” and we have to replenish the soil with fertilizers to keep the plants happy. “We apply these salts as fertilizers in our yards to help plants grow. The addition of these nutrients can be very helpful, but only to a certain level,” Hynes says. “Both synthetic and organic fertilizers have the capability to add too many salts to the soil, so it is important that you apply appropriate amounts to your soil.”
Plants have varying salt tolerances. Many of our common home and garden plants like Japanese maples are very sensitive and will be affected at even low salt values, but other plants like oleander can tolerate salt.
Signs of Too Much Salt in Soil
There are signs that plants are affected by high salinity in soils. This is due to the decrease in energy the plant has for growth:
– Stunted size
– Blue-green tint to the leaves
– Leaf tips appear burned
– Younger leaves are yellow or wilting despite adequate watering
The first step to correcting these saline soils is to diagnose the problem. If the symptoms discussed above appear on your plants and/or you know you get a little too enthusiastic with fertilizer application or driveway salt, you may have high salt content in your soil. A local soil lab test can verify this by running a salinity test. Typically, you can increase the amount of irrigation you apply to your plants to leach the salts below the root zone. Note: this will only work if you have soils that drain well. If you are in a drought-stricken area, you may have to wait for precipitation to accomplish this, which could take multiple seasons. If the issue is primarily sodium (also verified with a lab test) you may need to incorporate gypsum into the soil prior to leaching. Gypsum is calcium sulfate and helps with managing high sodium levels.
If all else fails, choosing plants for your yard that can endure higher salt content may help with an area that is beyond correcting. Adapting the plants to fit the soil may be ultimately the best way to prevent headaches in the long run. The result? The beautiful yard you always dreamed of where you can enjoy watching the sunset while eating your low-salt potato chips.
Source: Soil Science Society of America