Canola Roots with Isaac Madsen

Field of canola.

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Contact Issac Madsen via email at

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Episode Transcription:

[ Music ]

Drew Lyon: Hello, and welcome to the WSU Wheat Beat Podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. We have weekly discussions with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat Podcast, do us a favor and subscribe on iTunes or your favorite podcasting app. And leave us a review while you’re there so others can find the show too.

[ Music ]

Drew Lyon: My guest today is Isaac Madsen. Isaac is a postdoctoral research assistant in soil fertility at WSU. Today, his research is focused on canola seeding root response to banded nitrogen fertilizers. He is also working on canola root morphology in grazing trials as well as foliar micronutrients application timing in canola. Hello, Isaac.

Isaac Madsen: Hello, Drew.

Drew Lyon: So Isaac, in your work on nitrogen fertilizer banding, what have you found to be the impacts of fertilizer bands on root systems?

Isaac Madsen: Yeah, so most of my work, as mentioned, has been with canola, and a lot of what we’ve noticed is that, in canola, which is a tap-rooted crop, you’ll often kill the top, the taproot, with the banded nitrogen fertilizers, and this causes the whole root system to change, so you’ll get a lot of lateral branching that follows that. And so you might lose some of those advantages of having the taproot that you were going for in growing canola, so that’s something to consider. And we’ve also done a little bit looking at wheat, and what we found is the wheat sort of avoids the band, or it might lose one or two of its many fibrous roots because it has a different root architecture genetically. So it might lose one or two of those, but then it tends to recover and adapt a little better than canola.

Drew Lyon: Okay, so you kind of lose one of the big advantages I’ve heard of planting canola is getting that taproot to help bust its way through some hardpans, and open up the soil, and this banding could put that at jeopardy, I guess.

Isaac Madsen: Yeah, exactly. So what we found is that, especially with Urea, you’ll pretty much always damage the taproot. And so you’ll, you might even still get a canola stand. It might not be what you were hoping for, but you’ll get the canola plants to survive, but you won’t get those nice, big taproots.

Drew Lyon: Okay, so what would this finding suggest farmers should do if they want to apply full rates of fertilizer at planting?

Isaac Madsen: Yeah. So source is really important here. So Urea, we found that to be the worst out of the different nitrogen sources we’ve tried. So we’ve tried ammonium sulfate, Urea, and UAN Solution 32. Ranking those from the most toxic to the least, Urea causes the most damage to the root system, followed by ammonium sulfate, and then followed by UAN. We haven’t tried anhydrous ammonia, which is obviously a very popular product out here. My thoughts, my guesses on that are that, if you apply the anhydrous early enough beforehand, you don’t have any major problems because it’s allowed to dissipate in the soil prior to the root development if you’re planting a little later.

Drew Lyon: Is there anything they can do banding wise, like keep it farther away from the seed row or deep down, or what are some of the things they can do there?

Isaac Madsen: Yeah. Exactly. So in soil fertility, we always like to talk about the 4 R’s, which are rate, place, time, and source. And so, really, what we’re looking for is, you know, rates that are low enough, yet working on trying to figure out exactly what those are, but as far as placement, you can go to the side rather than directly below. So probably an inch and a half, two inches to the side, and you’re getting safe with canola. You also got to think about your drill and where it might be directing the roots to grow. So if you’re in a direct seeding situation and you’re using a hoe drill, there’s some thought that you might create a preferential path for the root to grow towards the fertilizer, you know, even in a paired row system. So that’s one thing to consider. But generally, I think if you’re two inches to the side and below, you’re probably fine. It’s directly below that you really want to be concerned about.

Drew Lyon: Does the soil type have any influence on this?

Isaac Madsen: Yes. So soil type does matter, partially due to how much nitrogen it’s going to lock up, but also the pH. So a lot of the thought is that it’s actually ammonia that’s causing the toxicity in these scenarios, and so a higher pH soil will cause more ammonia volatilization. And so Urea, when you dissolve it in water, has a pH of I think around 9, 8 or 9. It’s pretty high pH. Whereas ammonium sulfate has a slightly acidic pH. So that would possibly explain some of the differences there. And UAN is relatively neutral. So I think — you’ll also get salt toxicity issues, but those are kind of separate, and I think the root from what we can see is more tolerant of that than the ammonia toxicity.

Drew Lyon: So tell us a little bit about how you conducted this research to get at this because I see you walking around with all sorts of interesting equipment in the hallway, so maybe you can tell our listeners how you do that.

Isaac Madsen: [laughs ]Yeah. So we actually make videos of the roots growing into the bands using office scanners. So we put office scanners, we either bury them in the soil or we build them into a planting box in the lab. And that allows us to place the fertilizer and the seed precisely on the face. And then, essentially, we take repeated scans so we’re able to watch the roots grow into the fertilizer band. And so that’s pretty fun, and honestly, there’s not a lot of people out there doing it, which is kind of surprising because it’s cheap and it’s awesome. [laughs] So–

Drew Lyon: And is the warranty still good after you buried a scanner in the soil?

Isaac Madsen: [laughs] No, I wouldn’t think so. We go through a process we call voiding the warranty at the start of our experiments.

Drew Lyon: Very interesting. So in addition to your work with nitrogen fertility, I know you’re also interested in soil quality issues. Can you tell us a little bit about your take on soil quality indexes, such as the Haney Soil Health Score?

Isaac Madsen: Yeah. So I’m very interested in the soil quality, soil health discussion that’s going on right now in the NRCS and Broader Nationally. And I’m working on a project actually funded by NRCS to try and develop indicators for our area because I think indicators such as the Haney Test might not be the best tool for evaluating soil health in an area such as the Palouse where we tend to have these dry summers and the wet winters. And I think we see some biological fluctuations throughout our seasons that aren’t typical of other dryland regions. So what I’ve found is we tend to get very low scores on the Haney Test, and I have a feeling that has to do more with the timing of sampling than it actually has to do with the health of our soils and just the natural cycle of our soils. So Dave Huggins has actually done some great work on this, and he’s shown that things like permanganate-oxidizable carbon are more responsive than the Haney Test to, say, a field being a no-till. So I think we’re trying to look at other tests that might be more appropriate for this region.

Drew Lyon: Interesting. I know when I moved from the Great Plains, Nebraska to here, one of the things I noticed was that herbicide carryover was a lot more common here, and I think it’s because during those dry summers, you don’t get the bacterial and the fungal growth that we get in the summer rainfall zone. We don’t get those here.

Isaac Madsen: I would easily believe that that’s a reason that’s involved just because I feel like our topsoil during the summer isn’t near as active as you expect to find in different areas. We have summer rainfall.

Drew Lyon: So what do you hope to achieve by taking a large number of soil samples across Palouse and testing it? I assume you’re running these different soil quality indexes on all these samples.

Isaac Madsen: Yeah, sorry. So that’s our project that we’re going to be doing is across, just trying to stay in one soil series. So we’re trying to stay in the Palouse Silt Loam. We’re going to be looking at different locations where we have perennial grasses, and we have no-till, and we have tilled. And basically, looking at the whole bunch of different measurements. So some of them will be physical, such as aggregate stability, and some of them will be biological. We’ll be doing PLFA. But also, looking at things that I’m specifically interested in, like rooting depth, and depth of topsoil, and some of these other measurements that, when you’re only measuring the top 6 inches, you don’t really get to take a close look at. And in conjunction with that, I would like to look at some soil micronutrients. And so that’s kind of one thing I’m going to start looking at. As we’ve started piecing together all these various data sets that were laying around the department of, you know, micronutrients in your third and fourth foot and starting to look at those and see if those might be sort of a long-term indicator of soil health and sustainability in that way, so.

Drew Lyon: Well, I find what you’re doing to be very interesting. I know when I started graduate school, I was given the advice, don’t work on roots. They’re too hard to work on.

Isaac Madsen: [laughs] Yeah.

Drew Lyon: So seeing somebody who’s going in there and doing the hard work, and there’s a lot to learn, I imagine, and so I think you have a, perhaps a laborious future, but a very bright future in science looking at root systems. I think it really is the new frontier.

Isaac Madsen: Yup. I always tell my students, you know, go out in the field and dig a pit. And then, you’ll learn more than you’ll learn from me in class, probably, in lecture. Maybe that’s not good advertising, but I think it’s really true.

Drew Lyon: It’s a very interesting area. Thank you very much, Isaac.

Isaac Madsen: Yep, you’re welcome.

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat Podcast. If you like what you hear, you can subscribe on iTunes or your favorite podcasting app so you never miss an episode. And leave us a review while you’re there. If you have questions for us that you’d like to hear addressed on future episodes, please email me at You can find us online at You can also reach out on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat Podcast is a production of CAHNRS communications in the College of Agricultural, Human, and Natural Resource Sciences at Washington State University. I’m Drew Lyon. We’ll see you next week.