By Alex Straughn
For landscaping professionals, the quality of topsoil can make or break a project. Healthy topsoil provides the optimal pH, nutrient availability, moisture-holding capacity, and soil structure for plant roots to thrive. Fertile topsoil is key to sustainable landscaping success.
The top 3 to 10 inches is where most nutrients, organic matter and soil life are concentrated. Unlike the dense, mineral-heavy subsoil beneath, good topsoil is typically a loose, dark and crumbly mix of mineral particles, decaying organic material, microorganisms, water and air.
It has a balanced texture (ideally a loam with a mix of sand, silt, and clay) that promotes good drainage while retaining enough water for roots. It’s rich in organic matter (aim for ~3% or more) to foster beneficial soil organisms and to improve soil aeration and nutrient supply.
Without quality soil, even the most well-designed landscape will struggle to sustain itself. A layer of fertile topsoil helps prevent erosion by anchoring plant roots and absorbing rainfall. It limits stormwater runoff which means less flooding and less pollution washing into waterways.
Here are a few key roles topsoil plays in sustainable landscape management:
Nutrient Cycling and Reduced Chemical Use
Fertile topsoil naturally contains nutrients like nitrogen, phosphorus and potassium as well as trace minerals. Plants growing in rich topsoil often require fewer synthetic fertilizers because the soil food web (microbes, fungi, earthworms, etc.) is constantly releasing nutrients in plant-available forms. For example, a healthy soil ecosystem with ample organic matter feeds plants and even helps protect them from diseases, reducing the need for chemical inputs. Investing in soil quality up front can save money and effort later as robust plants in healthy soil are more vigorous and pest-resistant, meaning fewer treatments and replacements.
Water Management and Resilience
Topsoil with good structure acts like a sponge. The mix of particle sizes and organic matter creates pores that absorb rainwater and hold it for plant roots, while still allowing excess to drain. This improves drought resilience (lawns and gardens won’t brown out so quickly) and helps manage stormwater by preventing rapid runoff. In sustainable landscape design, features like rain gardens or bioswales rely on amended topsoil to increase infiltration.
Erosion Control and Soil Stability
Bare or thin soil is prone to erosion by wind and water. Retaining or adding topsoil is a fundamental erosion-control strategy in sustainable landscaping. Deep topsoil encourages deeper roots that physically hold the ground together on slopes and in heavy rains. This preserves the landscape’s shape, prevents gullying, and keeps sediment and the nutrients bound to it from washing into streams. Using compost or enriched topsoil on eroded areas has been shown to restore soil structure and significantly reduce further erosion.
Biodiversity and Plant Health
A diverse soil biota supports the nutrient needs of diverse plantings and can suppress soil borne pathogens naturally. Moreover, many native plants are adapted to local soil conditions. Preserving the native topsoil can help these plants establish more quickly. In practice, landscapers improve soil organic content through compost, mulch, cover crops, etc. to mimic a natural fertile soil, which in turn supports pollinators and soil fauna.
Challenges with Topsoil
If topsoil is so critical, why is it often lacking in new landscapes? The answer lies in common construction and landscaping practices. On many building sites, the rich topsoil gets stripped away or compacted early in the construction process.
Builders frequently remove topsoil to make way for foundations, basements and utilities. In a typical subdivision development, the beautiful top layer of soil that took nature centuries to build is scraped off and sometimes hauled away, leaving mostly subsoil behind.
So contractors often strip it off to reach more stable ground. However, the resulting challenge is that the remaining soil on site is often low in nutrients and organic matter and heavily compacted by construction equipment.
Many landscape contracts include importing topsoil as a line item. The American Society of Landscape Architects (ASLA) provides guidelines to ensure this topsoil is high quality. It should be free of weeds, disease pathogens, and stones, and meet standards for pH, texture, and organic matter content. If you accept sub-par soil, you’ll likely spend a lot of money and time improving it later for plants to do well.
Compaction is another topsoil challenge. Even when soil isn’t hauled away, the traffic of heavy machinery can press the soil so tightly that roots can’t grow. This often necessitates tilling or subsoiling to loosen the ground before landscaping. Best practices suggest protecting certain areas from traffic and stockpiling topsoil in designated piles during construction to later redistribute it.
1. Preserve and Reuse Existing Topsoil On-Site
If you’re involved early in a project, work with builders to stockpile the topsoil before grading begins. Store it in a safe place like a berm or pile, ideally not too tall to avoid smothering the soil microbes, and keep it covered or planted with a temporary cover crop so it doesn’t blow or wash away.
2. Import High-Quality Topsoil and Amend as Needed
In cases where the existing soil is just too poor or gone, importing topsoil is the next option. Always source from a reputable supplier and inspect the material. It should look and smell like healthy soil (dark, earthy, no debris). Check that it meets quality criteria: a neutral to slightly acidic pH (around 5.5–7.5 is ideal for most landscapes).
When adding topsoil to a site, about 4–6 inches of topsoil is recommended on new lawns to ensure a healthy turf root zone. Garden beds may need even more (8–12 inches) for deep-rooted plants. If you’re laying sod, don’t just dust the surface – provide enough depth of good soil for the roots to establish. It also helps to till or loosen the interface between the subsoil and new topsoil, so roots can transition downward and water doesn’t perch on the compacted layer.
3. Improve Soil Organically
Even after initial installation, encourage practices that build up the topsoil over time. This can include regular top-dressing of beds and lawns with compost, mulching with organic mulches, and planting cover crops or deep-rooted plants in off-seasons to enrich and aerate the soil.
4. Avoid Practices that Strip or Sterilize Soil
In maintaining landscapes, be mindful to protect the topsoil you’ve cultivated. Avoid unnecessary soil removal or aggressive grading that would strip the top layer. Minimize the use of heavy machinery on wet soil to prevent compaction. Also be cautious with chemicals. Overuse of pesticides can harm the beneficial organisms in topsoil, and excessive synthetic fertilizers can degrade soil structure over time.
Simple steps like using board paths for wheelbarrows or temporarily laying plywood for equipment can protect soil during maintenance work. And when adding features like hardscapes, try to disturb as little of the surrounding topsoil as possible, or plan to rehabilitate it afterwards.
Think of it like building a house. You wouldn’t skimp on the foundation. In the same way, wise landscapers know that investing in soil quality sets the stage for everything else. When you start with a base of rich, well-structured topsoil, plants root deeply and robustly, lawns stay greener with less water, flowers and trees resist pests better, and the whole landscape simply flourishes.
Alex Straughn is general manager at SFI Topsoil. He has been supplying pulverized topsoil to the Chicago area for over two decades. As an active member of Landscape Illinois and Chief Engineer, his commitment to industry standards makes him a trusted resource for construction and landscaping professionals.