Soil Health - The Benefits of Air Spading

Nick St. Sauveur, district manager of Cortese Tree Experts, a Davey company, in Knoxville, TN, discusses the practice of air spading and how it can help improve soil quality and health.

In this episode we cover:  

• What is air spading? (:41)
• Can a tree of any size be air spaded? (1:12)
• Air spading and volcano mulching (2:40)
• What does an air spade look like? (3:14)
• How much soil comes out of air spading a big tree affected by soil compaction? (4:02)
• Where do you look at a tree for compaction stress? (5:03)
• Tool that tests soil compaction (6:22)
• What does a property look like two years after air spading? (6:56)
• Is it harder or easier to air spade maple trees? (7:46)
• How can you improve soil quality? (8:20)
• What can you use to improve compacted soil? (9:25)
• How long have Nick and Cortese used biochar? (10:36)
• Are biochar and compost mixed or added separately? (11:35)
• General tree health and fertilization (12:00)
• Can homeowners do soil tests? (13:39)
• Deep root fertilizing injections (14:59)
• What's the most fun Nick has in his job? (15:54)

To find your local Davey office, check out our find a local office page to search by zip code.

To learn more about compacted soil and soil quality, read our blogs, How to Tell if Soil is Compacted Around Trees and What to Do and Why Soil Care Is Important For Your Trees.

To learn more about biochar, watch our How to Improve Soil Health with Biochar YouTube video. 

Connect with Davey Tree on social media:
Twitter: @DaveyTree
Facebook: @DaveyTree
Instagram: @daveytree
YouTube: The Davey Tree Expert Company
LinkedIn: The Davey Tree Expert Company 

Connect with Doug Oster at www.dougoster.com. 

Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you!

Transcript

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Doug Oster: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more, because here at the Talking Trees podcast, we know trees are the answer. I'm joined again this week by Nick St. Sauveur. He's a district manager for Cortese Tree Specialists, a Davey company in Knoxville, Tennessee. Hey, Nick. Welcome back to the show. How are you?

Nick St. Sauveur: I'm doing well, Doug. It's good to be back.

Doug Oster: You suggested air spading and soil conditioning. What is air spading? What do you use that for on a tree?

Nick St. Sauveur: Yes, great question. An air spade is an air-powered excavating tool that is hooked up to a compressor that allows for us to either explore around the base of the tree, look for girdling roots and defects in the root structure of the tree, but it also allows us to actually condition the soil and amend the soil without causing any damage to the roots.

Doug Oster: What size tree? Could that be done on any size tree?

Nick St. Sauveur: Yes, really any size tree. We provide air spade services to even newly planted trees that weren't planted correctly to trees that are several hundred years old, just depending on what we're looking at doing to them.

Doug Oster: When you get on-site, what would make you use an air spade?

Nick St. Sauveur: I feel like the biggest thing is-- well, I guess two major things, one of which would be soil compaction. If you have highly compacted soil around the base of the tree, you end up losing a lot of your pore space in the soil. We have to go in and break that up and till it and create that pore space back. The other thing that we see a lot of is smaller trees that were planted in the past, I don't know, one year to five years that weren't planted right or that were over-mulched. We have a suspicion that there may be girdling roots or something underground that may actually be inhibiting vascular flow to the top of the tree.

Doug Oster: Let's take first off if it's planted wrong, does that mean too deep?

Nick St. Sauveur: It can be too deep. Typically, it is too deep or over-mulched as well.

Doug Oster: The over-mulching is the V word, the volcano mulching?

Nick St. Sauveur: Yes, volcano mulching.

Doug Oster: You could take an air spade and blow that off there, get that root flare where it's supposed to be?

Nick St. Sauveur: Correct, yes. The problem that you end up having if a tree is planted too deep, let's say it's planted 6 inches too deep into the soil, is that you're going to have that depression at the base of the tree that you really can't do anything about. If you correct that early enough, you drastically increase the lifespan of that tree and you actually help that tree out tremendously.

Doug Oster: What does the tool look like? If you're coming to my house, what am I going to see?

Nick St. Sauveur: Great question. This tool is hooked up to a tow-behind air compressor, typically, a very large air compressor. The tool itself is just a long-- it almost looks like a pipe with a trigger on it. At the end of that pipe you've got an upside-down funnel to prevent soil from actually coming back on whoever's using it.

Doug Oster: It's just like high-volume air blowing out of that, I guess, right?

Nick St. Sauveur: Correct, yes. It's that simple. You don't cause any damage to the roots by using this tool compared to when you went in with shovels and whatnot.

Doug Oster: That's pretty cool. Let's say it's a big tree. Let's say we have soil compaction. How much soil is coming out of there? We're talking like a real big tree you could do this on, right? You could go all the way around it-- all the way up?

Nick St. Sauveur: Yes, correct. It depends on what we're doing to the tree. If we are doing a full soil invigoration under the base of that tree, we can disturb as much area as the ideal area to mulch. That would be all the way out to the drip line of this tree. We go in, fluff up basically the top 12 to 18 inches of soil, and then come back with compost and amendments and that sort of thing, till all that back in, and then lay a nice layer of mulch on top of that.

Doug Oster: Sounds like that would make a tree really happy. [chuckles]

Nick St. Sauveur: Yes, you get really good results pretty quickly to if a tree's been under a lot of, especially, compaction stress for a number of years.

Doug Oster: When you're looking at a tree, are you looking up, are you looking down for compaction stress, or both?

Nick St. Sauveur: Both actually. No, that's a great question. Sometimes you can just feel it by walking on the soil, how compacted it is. Here in East Tennessee we're dealing with clay soil all the time, especially on newer development where they go in and rip all that topsoil off, discard everything, and then they bring big pieces of equipment in there to build the houses. Almost all that soil is going to be compacted. You can also look up and you could actually tell by how much that tree is growing if it's under stress. Now, that's not saying that the reason why the tree's not growing a whole lot is because of soil compaction. There could be a lot of other problems there that we have to address.

If you have healthy soil, you have healthy trees and healthy plants. Most of the problems that you have in agriculture are a result of poor soil issues. The other thing too, which I don't want to forget about this, but if you have compacted soil, you can actually test that. There's a tool that we can use to test the compaction of the soil to make sure that it's in the proper range.

Doug Oster: Tell me about that tool. How does that work?

Nick St. Sauveur: It's a tool that we just-- it looks like a probe. We push that into the ground. There's two tips on it depending on your soil type. As you push that into the ground, it gives a reading of the compaction of the soil. There's a rating on there which tells you whether or not you're overly compacted or not. That's a sure-tell sign of you've got compacted soil. That test doesn't lie.

Doug Oster: Tell me, going back to a property two years after doing this, what the tree looks like.

Nick St. Sauveur: I have seen-- especially with girdling roots where I come out, I assess the tree, find out there's girdling roots there, and I just throw it out to the tree. I've seen some maples with massive girdling roots where the tree's been struggling for years. We come in and take those off. Even the following year, I've seen growth that goes from just inches to 2 feet in one grove season by coming in and actually removing those girdling roots and actually letting the vascular system actually do what it's designed to do.

Doug Oster: Nick, I was going to ask you about maples. I wasn't so sure about maples. Since they're so shallow-rooted, does that make it harder or easier to do the air spading?

Nick St. Sauveur: It depends how long it's been in that issue for or been dealing with those stresses. Here in Tennessee, I feel like everything's difficult because of the clay soil and how compacted it is. Sandier soils, it's going to be a whole lot easier to blow that soil away. A lot of it has more to do with the soil type than the actual tree species.

Doug Oster: An oak, a maple, a pine, regardless of how they're-- each one grows differently with its roots, but it's more about the soil when you're dealing with air spading. Is that right?

Nick St. Sauveur: Correct, yes.

Doug Oster: Let's talk a little bit about improving that soil. You've touched on it, but what's the number one thing? Is that you blow off-- how fast does this have to be done? How long can those roots stay exposed like that? Does it matter?

Nick St. Sauveur: Yes. When we come in with air spade, we're putting soil right back that same day. You do not want to let especially the fine root hairs to dry out. If it's going to be uncovered for too long, typically we'll try to water, come out with our spray truck or something and keep those roots nice and moist. Ideally, you do it either after a rain or we ask a client to irrigate the day before a little bit just to try to prepare for it, because they are going to be out there and exposed, and obviously roots aren't supposed to be sitting out in the open like that.

Doug Oster: What are some of the things that you're using? As I said, you've touched on it briefly, but what exactly are you putting in there? Does it depend on the situation, depend on the tree, depend on the soil?

Nick St. Sauveur: Yes. If you're dealing with compacted soil, the biggest thing is putting something in the soil that's going to help hold that pore space open. Probably-- everybody's heard about it. I feel like everybody that's in the green industry has heard about this nowadays, but biochar is being put in everything, and that helps to hold the pore space open in the soil, but also has a really high surface area so your microbes and everything can actually live in there. You get a lot of benefits from biochar. We also will use compost as well. Compost and biochar together with soil will not only give you the pore space that you need but also feed the microbes in the soil, which those microbes, if they're happy and healthy, they take care of the trees, which means you have happy and healthy trees.

Doug Oster: Let's talk about biochar. We've talked about it at length on the show, but it might be something new for listeners. How long have you been using it and explain what it is?

Nick St. Sauveur: Biochar, simply put, is basically charcoal. It's not exactly that, but just for layman's terms, basically charcoal that we put into the ground. We've been using it at Cortese for, gosh, probably three to four years now. The biggest thing with biochar is that it has to be activated somehow, so you can't just stick it in the soil because it can actually take nutrients out of the soil and hold onto it. It has to either be activated when you buy it, before you buy it, or you have to mix it with something and then inject it into the soil or till it into the soil somehow.

Doug Oster: When you're adding biochar and compost, are they added separately or are they mixed together first in some kind of formula and then all put in at the same time?

Nick St. Sauveur: When it comes to air spade work, we will dump bags throughout the drip line or the treatment area and then we'll till it all in together. We're typically not pre-mixing it and then dumping it out.

Doug Oster: Let's just talk in general about the health of trees. When we talk soil conditioning, let's talk fertilization too.

Nick St. Sauveur: A conversation I'm having quite a bit with our clients is I recommend fertilizing and they're like, "Oh, okay, do you just recommend 10:10:10 or what do you recommend?" A lot of that has to do with your actual soil conditions. You can take a soil sample, send it off, have it tested, know exactly what you're deficient for. Here in East Tennessee, we're typically deficient in phosphorus. We're typically adding that to the soil. Then nitrogen as well. Most of the fertilizers that we're using are high in nitrogen because they just don't stay in the soil. They're a gas. Unless you have a legume or something like that, that's actually fixating nitrogen and putting it into the soil. You just have that air exchange coming in and out of the soil and it doesn't stay there. That has to be added, at least in low quantities to ensure that you have proper growth and vigor over the course of the year.

Start with a soil test if you don't know. If you have a tree that's showing some sort of deficiency, whether it's chlorotic or just stressed out or something like that. I think I said it already. Most of that starts in the soil. If you take care of the soil, you have all the nutrients in the soil, you're going to have healthy trees. It's just like humans, if we take care of ourselves, we eat a healthy diet, we exercise, all that stuff, we're going to be able to put off sickness.

Doug Oster: Now, do you guys do the soil test or does the homeowner do the soil test or could it be either way?

Nick St. Sauveur: Either way.

Doug Oster: Like in my case in Pennsylvania, I could just go out and buy a soil test from Penn State Cooperative Extension, $10. Take my sample, send them to the lab and I get my results back. Now I know a scientific number on what to add, right?

Nick St. Sauveur: Yes.

Doug Oster: Is that how we're-- Okay, that makes sense.

Nick St. Sauveur: I'm glad you brought that up. Another thing too with trees, because a lot of people seem to treat their trees with their grass where they come out and broadcast fertilizer over their lawn. The problem with that is that if you broadcast under the drip line of your tree, anything like your grass, your ground cover, any other shrubs, they're typically going to absorb a lot of that before it even reaches the roots of your trees. Having an arborist come in and actually fertilize those that has a fertilizer truck with a probe on it that we're injecting 6 to 12 inches into the ground below the root zone of the grass, that's where you're going to get the most bang for your buck and it's going to be well worth the money spent because you're actually going to be fertilizing your tree at that point instead of just your grass.

Doug Oster: I've seen that done and it's amazing and I've seen the results too. Explain how that's done. I know you've got the probe, but you're doing it every-- kind of a grid pattern, right?

Nick St. Sauveur: Correct. Yes. We'll go out to the drip line of the tree and we'll set up a grid typically about 2 feet apart and we inject on 2-foot centers and that our fertilizer truck, like I said, is injected about 6 to 12 inches in the ground-- under grade, excuse me, under pressure as a liquid. What that does is when we stick it in the ground, it will fracture the soil and evenly distribute throughout the soil and then we take another 2 feet, we inject there and then you get not necessarily overlap, but they come really close together so you have a nice even distribution of that fertilizer in the root zone of the tree.

Doug Oster: We've talked in the past about how you got into this and what you get out of your job, but before I let you go I just want to ask you, what's the most fun you have in your job?

Nick St. Sauveur: Most fun I have? I really like just teaching people about trees. I'm a lifelong student, I'll always be learning something. I like teaching my clients about trees, how to take care of them. I like bringing new employees on, working with them, teaching them how to properly take care of trees, how to make proper cuts, why certain trees are doing certain things. I think by doing that, our team is better able to serve our clients, but also by me educating my clients, they're not going to get ripped off because they know better, whether they do business with us or not.

Doug Oster: Well, Nick, as always, good stuff. I certainly learned a lot. You taught me a lot, so that's a good thing. We'll talk to you next time around. Thanks again for being on the show.

Nick St. Sauveur: Thanks, Doug.

Doug Oster: It's always great to talk with Nick, that was some good stuff. Now tune in every Thursday to the Talking Trees Podcast. From the Davey Tree Expert Company, I am your host Doug Oster, and do me a big favor, subscribe to the podcast so you'll never miss a show, and if you've got an idea for an episode, maybe a comment, send us an email to podcasts@davey.com. That's P-O-D-C-A-S-T-S@D-A-V-E-Y.com. As always, we like to remind you on the Talking Trees Podcast, trees are the answer.

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