Conserving Topsoil

Conservation of topsoil is a basic principle in landscape and golf course construction. For golf projects, a shortfall of healthy topsoil at the post-shaping replacement stage is extremely common, often with significant implications to the budget. Respreading suspect or damaged topsoil is a risk not worth taking, as it will inevitably lead to later problems with the quality of the playing surface.

Topsoil is distinct from subsoil. Topsoil contains organic material and acts as a growing medium. Its physical and chemical properties differ from subsoil in colour, texture, acidity and nutrient status. Where doubt exists, sampling and testing can be conducted. Differentiating soil types allows topsoil of higher quality to be identified for use on critical playing areas, such as green approaches, green collars and bunker mounds. Soil types of different textures and fertilities should be kept segregated in storage and re-spread in areas similar to their original environment.

Soil can be damaged in storage. Good practice in handling will avoid many problems. Most importantly, the soil should be handled as little as possible — ideally avoiding the need to stockpile by stripping, transporting and replacing in the same operation. It should be moved only when dry and not frozen to avoid damage to the particles and voids that form its structure. Threshold soil moisture levels, above which work must be suspended, may be set and tested with a soil tensiometer. Conversely, when the weather is too dry, especially when combined with windy conditions, soil particles may be lost as dust.

If soil stockpiling is required, stockpiles should be sited on level, well-drained ground of similar soil type cleared of its own topsoil. Such stockpiles should be sited away from watercourses and other areas vulnerable to deposition of eroded soil. Stockpiles should have a high surface area to volume ratio, should be free of weeds, are not trafficked by machinery once formed, and remain in place for no more than eight weeks.

If the vegetation won’t be replanted, it’s normal to pre-treat soil with an herbicide before soil removal. When the vegetation has died back, the soil should be rotovated prior to stripping. During stripping, other materials may be revealed underneath, including organic material, sand and gravel. Provided quality can be tested as suitable, these materials may be re-used — for example, in the construction of greens and tees — to reduce costs and improve the overall environmental sustainability of the project.