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Talking Trees Live: Soil Health with Davey Expert Chris-Fields Johnson

Technical Advisor at The Davey Institute Chris-Fields Johnson gives the run down on the importance of soil health and why it is important for your trees’ and plants’ overall health.

Why Do Soils Need Amendments?

Usually we are working in an urban environment where it has been changed by humans.

There are two big things that happen to the soil: (00:03:41)

  • Organic matter declines
  • Compaction happens from foot traffic, vehicle traffic

What is the Problem with Soil Compaction? (00:04:13)

There are major issues with soil compaction:

  • The roots cannot physically penetrate the soil when it’s overly compacted.
  • Compaction is pushing the air pockets out of the soil so air can no longer move through the soil

Our roots need to breathe, they need oxygen to survive so if you compact the soil over existing roots, they often aren’t able to get the oxygen they need, and die in place.

Here’s how to tell if soil is compacted around trees and what to do.

What are the Good Ingredients in Soil?

Chris explains to think about it as a lasagna or Sheppard's pie. There is going to be different layers. (00:08:05)

Soil is primarily made from mineral matter derived from the geological materials on the site. The other part of it is organic matter that depends on the climate and how well the soil is drained.

Fun fact: The colder the climate, the more organic matter exists because during the cold temperatures in winter, organic matter does not decompose. It freezes. (00:09:06)

Air and water are also key ingredients. (00:09:56)

Why You Need a Soil Test

Soil tests help properly diagnose issues with your plants, especially if it’s not immediately obvious. If you don’t correct the limiting factors in the soil, it won’t improve the health of the plant. (00:14:00)

What Organic Matter Should We Add to Soil?

There are lots of ways to rebuild your soil to get it back to its natural forest-like type of state. (00:15:26)

  • Mulch at the surface to gradually increase organic matter (greater details at 00:42:50)
  • Directly incorporate materials like compost and biochar into soil to recreate the A-Horizon (topsoil).
  • Inject a liquid form of the organic matter into the soil to help with the soil aggregates

What’s the difference between compost and biochar? (00:18:15)

Biochar has low nitrogen content versus compost will have a good balance of nitrogen.

Also, when you add biochar to soil it’s a permanent soil amendment, versus compost which will decompose.

Just to name a few of the many benefits of biochar:

  • Helps with nutrient retention
  • Remediates salt and heavy metals in the soil
  • Prevents soil compaction

Biochar can be used in lawn care and vegetable gardens too.

Fall Fertilization and Organic Matter Injections

Often nitrogen and phosphorus are usually the most limiting nutrients to trees. (00:34:46)

You want to make sure it is a slow-release form, especially for nitrogen. Too much nitrogen can create problems.

A soil test will tell you what your soil needs.

If you want to encourage root growth, now is a good time to give the trees all that they need so they don’t run into any issues.

Viewers Questions

Can you buy biochar at the store? (00:24:20)

You can purchase it at your local garden store or larger landscape suppliers.

Can you use Aquarium Charcoal to obtain the same results as biochar? (00:26:56)

Aquarium charcoal is activated carbon, which is a lot like biochar but an upgraded version. It is specially processed to activate the charcoal to give it more surface functional groups and surface area to be even more efficient in absorbing nutrients.

Should I put compost in during the winter and not during the spring? (00:28:30)

It depends on the context. There’s not a fundamental problem with putting it down in the spring.

If the compost has too high or low nitrogen, putting it down in the winter will give it time to balance out with the landscape around it before there’s a strong demand from the plants.

When planting a new tree, should we add biochar or compost to the hole? (00:30:50)

It depends! If your soil is high in organic matter and has no compaction issues, then your tree should be fine without adding anything. Assuming the tree is appropriate for your region and soil type.

On the other hand, if it’s in a new development with no organic matter and a severely compacted site, then planting a tree with no soil amendments may cause the tree to struggle.

Do newly planted trees benefit from adding mycorrhizae spores? (00:37:40)

It’s not terribly important, and often not effective.

However, if you’re trying to plant in a relatively sterile site (new development with engineered soil, land reclamation site) or in an exotic location where the selected species has never been planted, the best strategy is to use soil from the place where the trees are already growing so you know you have all the associated microbes.

How can I get rid of Pear Rust? (00:45:02)

You can do things to increase the light and air within the canopy of the trees with a proper pruning program.

Avoid any overhead irrigation and have a fungicide applied during the spring while new leaves are developing.

How frequently should we add compost or biochar? (00:47:26)

It can be a one-and-done type of thing if you take the proper steps.

If the tree is growing properly, it will naturally increase organic matter over time.

You can always do a soil test to check the organic matter in your soil.

The Davey Institute

The Davey Institute is the academic and research department within Davey. (00:05:20)

It supports the local arborists with research and training on tree pests and diseases to provide proper management plans and diagnostic issues.

What does that mean for you as a homeowner?

This ensures our work is to the highest quality of service in our industry. Davey’s technical teams are staffed with experts like Chris to address your specific needs.

Upcoming Talking Trees Live Series

Tune in for the next Talking Trees Live event! Each series will explore various tree care topics from damaging tree insects and diseases to landscape best practices and seasonal tree care tips. 

Have all your questions and concerns ready! You can ask them all live during the streaming interview. 

Be sure to ‘like’ Davey’s Facebook page to access the Talking Trees series live.

Don’t have Facebook? No worries, you can access all the past videos here.

>>> Check out the schedule here for upcoming Talking Trees Live topics!

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