At the time of this writing, scientists do not consider selenium to be an essential plant nutrient. However, it is definitely beneficial because it stimulates growth and gives plants resistance to a variety of stressors:
- Herbivore pressure.
Some soils are naturally rich in selenium. Pockets of such soil occur in many states. States that typically have higher selenium levels overall include:
- North Dakota.
- South Dakota.
Supplemental selenium can be added in the form of volcanic ash or saltwater-based fertilizer. The manure from animals fed selenium supplements is another potential source.
Some soils, usually those in areas with high rainfalls, are naturally deficient in selenium. Others become that way after years of poor farming practices.
Plants generally do not show symptoms of selenium deficiency. It is mostly a problem for the people and animals who consume the crops.
Should selenium deficiency become an issue in your field or garden, consider boosting soil nutrient levels with one of the natural fertilizers mentioned above.
Selenium toxicity can be the result of contamination from industrial sources. It can also occur naturally in some soils.
Be aware that different types of plants respond very differently to excess selenium levels. Some plants can absorb large quantities with immunity, while others are killed outright by contamination with even small amounts of selenium.
Symptoms of selenium toxicity in plants include:
- Stunted growth.
- Dry, pale, withered leaves.
- Early death.
If the problem is with outside contamination, the solution is to identify and address the source of the difficulty. In locations where the soil selenium levels are too high naturally, there is less that you can do. You may simply need to grow crops with a higher tolerance for selenium. Just be aware of the potential harmful effects that consuming plants grown on high-selenium soils may have on the health of the people and animals who consume the plants. Consider container gardening. Toxicity in livestock can be avoided by the following precautions:
- Exclude animals from pastures infested with selenium-accumulating weeds.
- Allow livestock to graze more selectively, as most healthy animals will avoid toxic plants if given the choice.
- Provide adequate water and minerals so that livestock are not tempted to eat toxic weeds to met their dietary needs.
Selenium in Counties of the Conterminous States
A map showing selenium levels in soils per county.