Structural Soil for Urban Trees
Currently most urban trees are planted directly into existing compacted urban soil or tree pits with limited root space. Trees that are planted in areas surrounded by paving tend to struggle for air space and usually decline well before they should. Where soil volume is limited by pavement, tree roots suffer and tend to take the path of least resistance searching for air, usually in and around pipes, foundations, or to the surface. Healthy trees need a large volume of non-compacted soil with adequate drainage and aeration and reasonable fertility.
While the need and desire for large trees in the urban landscape still is the desired intent, the trees do not survive long enough to fill the need. Not planning for root growth is ignoring the biological requirements of trees and is not economical or environmentally prudent. The failure to provide adequate soil for both drainage and root growth is critical to the life of the tree and without an engineered soil specific to this application, trees have a shortened life span and may die. Ensuring a good supply of air to the tree roots is essential for satisfactory tree growth, however in urban situations, the movement of air into the soil is often restricted. By providing additional root space below the pavement in what otherwise was compacted urban soil, Structural Soil can allow most newly planted trees to have a chance for healthy growth. This mix consists of 80% 75 mm angular clear aggregate and 20% approved sandy clay loam. The aggregates bear the load, providing the structural stability for the pavement above. The angularity of the rock create for the non-compacted soil, providing space for air, water and nutrients the roots, as well as provide for future root expansion. Engineered structural soil provides a resource for root growth beyond the traditional tree pit, allowing for much stronger root growth and ongoing tree health.
Denbow has been providing structural soil to many municipalities within the Greater Vancouver and Fraser Valley area. These departments use Denbow’s manufactured soil to allow city planners and engineering departments to add trees for the health and beauty of urban communities.
Contact Denbow’s soil experts today to find out more about how structural soil can work in your city or municipality.
Best Types of Compost for Landscaping – Ask Tom
What types of compost for landscaping?
There are a number of beneficial composts available for the local landscape projects, and the choice should depend on what the compost is being used for.
So what are the best types of compost for landscaping? There are composts in the marketplace that are specifically based on mushroom manure which is plentiful in our area. Mushroom manure can be useful but it can also be overused. Clean green compost, which is made of clean green waste and debris, is one of the more pristine composts in our marketplace. Other large sources of municipal compost are available and; those are appropriate for certain uses, typically larger remediation and possibly landscaping.
How do you know you’re getting good compost?
Good-quality compost has a number of characteristics. It’s usually brown and black in colour, but the colour is just one benchmark. The compost should have a reasonably good earthy smell, not an overly rotten smell like manure. Also important is the supplier should have an analysis available. Quality suppliers will regularly have their product tested and have soil analyses available for the end user.
Why is compost an important part of the soils being used?
Compost-based soils made with clean quality compost should be the top choice for landscape projects.
Compost is the important organic matter that helps the soil to function in a number of ways. It provides water-holding and nutrient capacity, providing for overall plan health.
Be selective when specifying or purchasing manufactured or engineered soils; for many projects, the best or only opportunity to provide plants or seeds with the best nutrition is during the initial installation.
What is Structural Soil Why is it good for Trees?
Why is structural soil effective?
Structural soil is a type of soil mixed with a specific type of gap-upgraded rock (typically 75mm clear). This is a very important part of the specification; the reason structural soil works well is that the gaps created by the rock are then filled with soil, enabling penetration by tree roots. This penetration allows the tree access to a larger space underground, and has the double function of preventing the tree roots from lifting up the hard surface, i.e. the sidewalk that is on top.
How does the structural soil get tested?
The testing of structural soil is essentially a three-part process. The soil must be tested separately. The rock must be tested and sourced with a specific sieve size attached to it to determine that it is in fact a clear rock and not a minus rock. With a minus rock all of which would be filled and therefore the soil would be effective.
There is also a stabilizing compound that is used with structural support to help the soil adhere to the rock. The specifications for this material would come directly from the stabilizer supplier; there are more than one of these.
Who can make structural soil?
Like any engineered soil, structured soil is a technical process which is best done by people who understand all the specific components and have all the components readily available with testing and prior knowledge. Making good structural soil to specification is an extremely important endeavour. Structural swell that is not up to specification is a very difficult situation to remediate once it’s already in the ground.
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Dealing with the Chafer Beetle – Nematode Protocol Update
Two options for addressing chafer beetle infestations
Are you or your clients having problems with the European Chafer beetle destroying lawn? We suggest the protocols described below. Please keep in mind that the insecticide must be administered by a professional with a pesticide applicator’s certificate. The rest could be done by a homeowner, but it is a procedure that is far more likely to be done by a landscaper.
The first option is to do an Imidacloprid drench. After the drench, wait a few weeks, then remove the turf and as much soil as is reasonable—a minimum depth of 2 inches. Next, add soil to required depth; the soil can either be Terraseeded, hand seeded, or lay sod. Make sure to do this in late July/early August before applying the nematodes.
By removing the turf and some soil, you’re taking out most of the grubs, even the ones killed by the Imidacloprid. The large grubs are more difficult for the nematodes to kill. Applying nematodes after egg-hatch (in mid-late July) will target the small grubs, which is more effective. It should be emphasized that nematodes should be applied annually if the Chafer Beetle continue to be a problem in their area.
There is the issue that not all jurisdictions allow the application of this insecticide. Therefore, each customer must find out what is acceptable within their jobsite and municipality.
If insecticide use is not permitted in the area, there is a second option. First, apply the nematodes at recommended rates to the soil in April through June, and then again in September through early November; the nematodes should be applied in areas of known infestation where specific lawns show signs of chafer infestation. Remember that the lawns must remain damp for at least two weeks after nematode applications.
For both options, it is very important to follow healthy lawn practices as well established lawns are more resistant to chafer damage. These practices include aeration and topdressing, watering well at appropriate intervals, consistent fertilization, and cutting to a 2-inch height (not too short).
In order to resist the chafer beetle when projects are newly installed, consider the following recommendations. First, if permissible, drench the soil with Imidaclorprid. Then, excavate and dispose of native topsoil to a reasonable depth of 2-6 inches. Replace the excavated material with compost-based soil; the type of soil should be based on specific requirements, i.e. turf. If applicable for the application, the use of grass species such as tall fescues and alternatives such as Microclover will help resist the beetle. Overseed the remediated areas at 3-4 times the suggested rates; in theory, this makes it difficult for the chafer to get to the surface. It will also make it harder for the chafer predators (birds, raccoons, etc.) to do damage. Lastly, encourage the use of any product or method that will increase turf establishment as well-rooted turf will stand a better chance.
Overall, it is important to remember that the European chafer beetle is an ongoing problem that is unlikely to be solved easily. There is no silver bullet. Providing quality products and installation combined with a willingness to maintain the remediated areas will improve the customers chance of a successful project.
Check out our full infographic on “How to Deal with the Chafer Beetle”. Enjoy and please share!
Here are some other resources we have found online that may be of help:
Soil Series – Who is this Tom? segment #2023
“Dirt is the stuff underneath your fingernails, whereas soil is an engineered composition of organic matter (sand, clay and organic matter) designed specifically for your project’s grow media and geographic location.”
– Tom McConkey
So who is this Tom McConkey?
Before we start talking about “soil”, we want to introduce our specialist. Denbow is pleased to be offering this series of interviews with one of our valued partners, Tom McConkey. Tom is highly skilled in landscape and our local soil and has been in the field for over two decades. Some of his specialty areas include Green Roofs, Urban Agriculture, Bio-Swales, Storm Water Management, Sustainable Turf Grass Practices.
Tom attended Carelton University and earned a degree to become an English teacher but as fate would have it, Tom decided to take a position at a local landscape company instead.
Early on there he got involved in the company’s compost practices. Tom became very interested in not only selling the compost, but understanding the composting process.
At the time, composting was a new aspect of the landscape industry so Tom was given the freedom to get to really “dig in,” so to speak.
During his early years, Tom was able cultivate his knowledge and skills while being mentored by Dr. Bill Herman of Pacific Soil Analysis. Dr. Herman is a soil specialist who instructed Tom in both the composting process and more importantly, the beneficial use of organic matter as it pertains to the British Columbia Lower Mainland network.
Denbow hopes this interview series with expert, Tom McConkey serves Landscape architects, city managers and landscapers as well as the average joe gardener in understanding the complexity of engineered soil and how it can assist their projects.
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