Sodium bicarbonate, commonly known as baking soda, is an inexpensive, naturally occurring salt often found in the kitchen pantry. This white powder has an alkaline pH when dissolved in water (NaHCO3). Its basic chemical properties allow it to interact with organic matter, making it a popular choice for addressing various turfgrass problems.
Controlling Lawn Fungal Diseases
One primary use of a baking soda solution on turfgrass is managing common fungal infections. When applied to the grass blades, the sodium bicarbonate elevates the pH on the leaf surface, creating an alkaline microenvironment. This abrupt change in pH is highly disruptive to many fungal pathogens, such as those that cause dollar spot, brown patch, or powdery mildew. The sudden shift makes the turf surface inhospitable for fungal growth and germination.
Beyond altering the pH, the bicarbonate ions actively interfere with the internal biology of the fungal cells. This action disrupts the ion balance within the fungal spores, which is essential for their survival and reproduction. The resulting cellular stress can lead to the breakdown of the fungal cell walls, effectively making baking soda a contact fungicide. Because of this mode of action, the solution must directly cover the infected area to be effective against the fungal growth.
The application is most successful when used preventatively or when a fungal outbreak is in its early stages. Once an infection is well-established, the concentration needed for control may risk damaging the grass. The solution is typically mixed with a small amount of horticultural oil or liquid soap, which acts as a surfactant. This additive ensures the mixture spreads evenly and adheres to the grass blades, keeping the agent in contact with the spores.
Impact on Broadleaf Weeds
Baking soda is also used as a non-selective herbicide, targeting small, unwanted broadleaf plants like clover or young dandelions. The mechanism by which it kills weeds is fundamentally different from its fungicidal action, relying on its high sodium content. When applied directly to plant foliage or the soil surface, the sodium acts as a salt, causing severe desiccation.
The high concentration of salt draws moisture out of the plant cells through osmosis, dehydrating the tissue. This rapid water loss causes the weed’s foliage to wilt, turn brown, and eventually die. Because this process is non-selective, baking soda will harm any plant it contacts, making it best used as a spot treatment.
The most effective method for weed control is applying dry baking soda directly onto the dampened leaves of the target weed. Wetting the foliage first helps the powder stick to the plant surface, initiating desiccation quickly. This method is only successful on small, young weeds with shallow root systems, as established plants often recover from surface damage. Applying too much or treating a large area introduces excess sodium into the soil, which can inhibit turfgrass growth.
Ensuring Safe Use and Preventing Grass Burn
The primary concern when using sodium bicarbonate on a lawn is the potential for sodium toxicity, commonly called “salt burn,” to the turfgrass. Since baking soda is a salt, overuse or excessive concentration can damage the grass blades, leading to yellowing, browning tips, or even patches of dead grass. Careful application and proper dilution are necessary to minimize the risk of injury to the lawn.
For liquid fungicide applications, a common ratio is mixing one tablespoon of baking soda into one gallon of water. Many recommendations include adding a few drops of dish soap or a teaspoon of vegetable oil to help the mixture stick. This solution should be sprayed lightly, ensuring thorough coverage of the affected area without saturating the soil.
Environmental conditions significantly influence the risk of grass burn. Applying the solution during the hottest part of the day, especially in direct sunlight, can amplify stress and increase the chance of damage. It is better to apply the solution in the late afternoon or evening, allowing the mixture to work overnight before the next day’s sun and heat. Because the product is water-soluble, reapplication is necessary after rain or heavy irrigation to maintain effectiveness.
Spot Treatment Testing
For spot-treating weeds, apply a light dusting of dry powder only to the weed foliage, avoiding surrounding grass. It is advisable to test any new solution or application method on a small, inconspicuous patch of lawn first. Observe the test area for 24 to 48 hours for signs of yellowing or stress before treating a larger section. If the grass shows damage, flush the area with plain water to wash the excess sodium from the plant tissue and soil.