Advice

How can you tell if your soil is water-repellent?

If you want to overseed a lawn that has suffered from the drought, first do a small test to see if the soil is water-repellent. Sufficient water is indeed essential for both the germination of the lawn seed and the subsequent growth of roots and above-ground parts.

Perform the following test to find out if your soil is water-repellent:

It’s important to address the water-repellent properties of the soil before overseeding. This can be achieved with DCM INTRO® 2.0

Step 1

Dig up a patch of grass with soil and grass roots.

Step 2

Apply a drop of water every 2-3 cm.

Step 3

If it takes longer than one minute for the drop to be absorbed into the soil, the soil is too water-repellent for effective lawn recovery. It is useless to sow grass seed in such water-repellent soil.

Causes & consequences

Water-repellent soil (hydrophobic soil) is characterized by poor water penetration into the top layer and uneven water distribution across the soil profile. These problems are caused by water-repellent substances (fungal hyphae, exudates from microorganisms, root residues, moss or thatch, etc.) that settle around soil particles. As a result, the latter are covered with a water-repellent (hydrophobic) layer that prevents rainwater from penetrating the soil.

In lawns, this type of drought stress problem often appears in patchy patterns. This means that in some areas water is still penetrating the soil, while in others it no longer does. In the latter case, rainwater will remain on the surface for a longer period and a large part of this water will have evaporated before it can penetrate the soil. If the grass field or lawn is on a slope, the rainwater can also run off to other areas that are not (yet) water-repellent.

Under the influence of gravity, water always chooses the easiest path, and during drought stress it will mainly penetrate through the largest pores the soil. So-called "preferential channels" are formed. A significant part of the water will drain away through these channels, while other areas of the soil remain completely dry. The negative consequence of this situation is a non-homogeneously moistened soil profile. Compared to areas that are not (yet) water-repellent, the amount of water that penetrates the soil during each rainfall or watering will therefore be increasingly lower in the water-repellent areas. This means that the problem of dry spots in lawns becomes worse during dry and warm periods. Watering abundantly is not enough to solve this problem.

The lawn will not benefit from the water supplied via the irrigation system or during a (heavy) rainfall because most of the water does not penetrate the top layer and is lost through evaporation, drains to lower areas on sloped lawn or penetrates the soil locally via a preferential channel and without moistening the rest of the soil profile. Consequently, the water is not available to the plant roots. Continuing to water or giving extra water is not a solution. The water-repellent nature of the soil must be addressed first.

Characteristics of drought stress

uneven growth and abnormal grass colour
yellowing followed by browning grass, often in patches (localised dry spots)
the appearance of thin and bare patches
increased susceptibility to diseases

Drought stress due to water repellency of soil particles occurs most rapidly on sandy soils and top layer mixtures for grass sports fields. The specific small surface area of sand grains and the large pores between the grains are responsible for a low capillary action and a limited water holding capacity. A lack of water and the associated symptoms of drought stress are therefore more likely to occur in lawns on sandy soils and in grass sports fields and golf courses (greens, tees, fairways), which often have a sandy structure.

After a period of higher temperatures (heat wave), water no longer penetrates the soil or penetrates it very slowly.

The solution? DCM INTRO 2.0, the 100% organic wetting agent.

DCM INTRO® 2.0

Watch the following video to clearly see this effect:

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