How To Use Wetting Agents To Fix Localized Dry Spot

Drought events create major constraints for water availability across the United States. While drought events often impact farming and food production, they also profoundly affect urban and suburban areas where turfgrass is a primary irrigated ground cover. In these systems, healthy turfgrass reduces erosion and runoff by stabilizing the soil, and transpiration (i.e., water uptake through the turf plant and out the stomata) creates a cooling effect that reduces temperatures and urban heat island effect.

When drought threatens water availability, soils can dry to the extent that turf either goes dormant or dies, negating the positive impact of turfgrass in these ecosystems. In addition, once soils become dry, they can develop water repellency or hydrophobicity, which makes it extremely difficult for water to penetrate and re-wet these soils. 

Drought monitor visualized how widespread drought is in the USA weekly.
Drought Monitor visualizes how widespread drought is in the USA weekly.

Soil Hydrophobicity

The water repellency is caused by microbiota and decomposing organic matter from the turf in the soil. They create an organic coating on the hydrophobic soil particles. The image below is a microscopic image of a sand grain with a hydrophobic coating. 

soil particle with organic coating
Sand grain with organic coating. Photo credit: Glen Obear
soil particle
Sand grain with hydrophobic coating

The turnover of soil microbes and decomposition of organic matter in the soil creates organic compounds that can coat soil particles and cause water-repellency or hydrophobicity (image above). These coatings are especially prevalent in sandy soils, including golf course putting greens. Once these coating form, it is challenging to wet the soil, and plants growing in these environments can experience extreme water stress. Therefore, wetting agents are a crucial tool to help overcome soil hydrophobicity.

Localized Dry Spot (LDS)

Soil hydrophobicity does not occur evenly across a turf stand. The uneven distribution of hydrophobicity creates an irregular water stress pattern, leading to Localized Dry Spots (LDS).  Water doesn’t penetrate the hydrophobic areas with LDS, but the areas adjacent to the LDS will absorb water normally. Once the soil moisture distribution is uneven, overhead irrigation worsens this effect. As a result, turf managers resort to labor-intensive hand-watering of dry spots to avoid overwatering other areas. Wetting agents can alleviate LDS and are a valuable tool for improving soil moisture uniformity across a turf area.
A turfgrass area with severe LDS

Wetting Agents

Hydrophobic soil with wetting agent

The hydrophobic coatings around soil particles can be treated with various types of soil-wetting agents. 

Wetting agents contain “amphiphilic” molecules with a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail. These molecules create bridges with the organic coatings surrounding the hydrophobic soil and reduce hydrophobicity. 

The reduction of hydrophobicity improves water penetration into these soils. Applying soil-wetting agents improves soil moisture uniformity across turf stands, and the benefit of the application can last for several weeks. Even soil moisture distribution leads to a more even, healthy turf stand, and less labor is required to irrigate and maintain these areas.

Hydrophobic soil with a droplet of water (right) and water and wetting agent (left)
Hydrophobic soil with a water and wetting agent containing droplet (left) and water alone (right)

The video below shows the behavior of water with and without Lateral, a wetting agent that fights LDS on turfgrass. The top half of the video is turfgrass affected by LDS, and the bottom half is well irrigated. In both cases, the water with Lateral will penetrate the soil easily to reach the root zone of the grass.

Lateral helps treat and prevent Localized Dry Spot

Lateral is a soil-wetting agent that reduces soil hydrophobicity and helps prevent localized dry spots. It is available in a liquid formulation to treat larger areas or granular for broadcast applications.

Lateral, Soil Wetting Agent

Lateral lowers the time it takes for water to penetrate hard-to-wet soils.

    • Improves soil moisture uniformity
    • Reduces hydrophobicity and localized dry spot (LDS)
    • Increases water infiltration and penetration
    • Increases water-use efficiency
    • The highly concentrated formula allows for more flexibility in use-rates

Lateral is available as liquid and a dry granular product.