Relationship Between Soil Depth and Weed Growth

Below is an extract from an article by Nishanta Rajakaruna and Robert S. Boyd, in Encyclopedia of Ecology (Second Edition), 2019, which perfectly highlights the importance of removing soil from hard surfaces and why this is the foundation of a successful weed control strategy.

"Soil depth can greatly influence the types of plants that can grow in them. Deeper soils generally can provide more water and nutrients to plants than more shallow soils. Furthermore, most plants rely on soil for mechanical support and this is especially true for tall woody plants (e.g., shrubs, trees). A classic example of the influence of soil depth on plant communities is seen on granite rock outcrops in the southeastern United States. As the granite weathers, it can form pools of soil that vary in depth from a few millimeters at the margin to tens of centimeters in the middle. The shallow marginal soils support certain annual plants, whereas deeper soils support herbaceous perennials and still deeper soils are colonized by woody plants. Plant zonation in these soil pools can be striking (Fig. 1)."

Fig. 1.

"Fig. 1. (A) A small soil pool (about 2 m wide) on a granite outcrop in east-central Alabama. Shallow soil at the margins is dominated by lichens. The deepest soil in the center of the pool has been colonized by Senecio tomentosus, a yellow-flowered herbaceous perennial species. (B) A larger soil pool on the same granite outcrop shown in (A). Deep soil on the left (behind the children: Jenny and Kristina Boyd) is occupied by woody plants (shrubs and trees). The soil pool becomes more shallow to the right, where striking zonation of smaller plants can be observed. The most shallow soil on the extreme right is occupied by the small red-colored annual Sedum smallii. Slightly deeper soil to the left of the Sedum zone is dominated by moss (Polytrichum commune) and white-flowered annual Arenaria species. Still deeper soil between that zone and the woody plants is dominated by perennial grasses along with some Senecio tomentosus."

In an urban environment, soil builds up on hard surfaces over time from decomposing organic matter such as leaves and grass clippings. 

The longer this is left between removal, the deeper the soil will become - allowing for more persistent perennial or even woody plants to establish themselves. If we can prevent the soil buildup by removing it with a sweeper or weedbrush, we can restrict the types of weeds that are likely to emerge making them much easier to control. 

If we can keep the soil depth no more than a few mm, we can severely restrict the growth of more challenging weeds, such as perennials and invasive plants. This is important if we are looking to reduce our reliance on chemicals such as glyphosate, as alternative treatments such as heat are much more effective on annual plants and plants commonly found in very shallow soils.

Kersten sweepers and weed brushes are great at maintaining hard surfaces by removing detritus and debris which reduces weed growth and is fundamental to Integrated weed management.

For much more information on weed prevention please take a look at our new Weed Prevention Guide for the Amenity Sector

You should also check out our 4 step plan to phase out glyphosate.

More information on Kersten Weed Brushes can be found on the Mechanical Weed Removal Page.

Contact Kersten to chat about your requirements.