From the Field: Evaluating wheat variety impacts on canola with Dr. Clark Neely

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Episode transcription:

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Drew Lyon: Hello, 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. In each episode, I speak with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production.

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My guest today is Dr. Clark Neely. Clark is an extension cropping systems agronomist based in Pullman, Washington, with the Crop and Soil Sciences department. He received degrees from Penn State, University of Idaho, and Texas A&M University. He worked for six years at Texas A&M University as the statewide small grains and cool season oilseed extension specialist before coming to WSU in 2019.

Some of his current research projects include looking at the impacts wheat variety has on subsequent spring canola performance, the impacts different crop management practices have on crop performance and micronutrient content of grain, and documenting seed size impacts on wheat performance. Clark also teaches the Advanced Cropping Systems course for the department. Hello, Clark.

Dr. Clark Neely: Hi, Drew.

Drew Lyon: So, we’re going to talk a little bit about a study you’ve been working on for a number of years on evaluating how wheat varieties affect subsequent canola crop. Why did you decide to do a study like that?

Dr. Clark Neely: Good question. So, I was kind of exposed to this when I was working at Texas A&M. They were trying to build canola acres–winter canola acres actually– down there at the time. And, they were seeing some anecdotal evidence from growers that following certain wheat varieties, they had a lot more difficult time getting canola established.

And so, they started doing some research, and I was involved in some trials with Curtis Adams as well down there. And we were seeing differences. And it’s actually pretty common in the literature. It’s been very well documented actually; wheat produces a variety of allelopathic chemicals that have been well documented in controlled settings like the greenhouse or lab settings, but there hadn’t been a whole lot done in the field. And so, they had done some work and they were documenting some differences in field research trials. I think in one article I read that as many as like 30% of the wheat varieties, they were seeing some detrimental impacts on early growth of the canola following those varieties.

So, you know, that was all hard red winter wheat, germplasm adapted for the southern Great Plains. To my knowledge nobody had really looked at that here in the northwest because we grow soft white winter, which is fairly unique. So, I thought it warranted looking at.

Drew Lyon: Okay. I’m always a bit skeptical about allelopathy because you read about it a lot, and it very well could be allelopathy. Are there any other thoughts on what else might influence how well canola establishes behind a wheat variety, like, I don’t know, how the residue breaks down or doesn’t break down?

Dr. Clark Neely: Exactly. Yeah. And I’ll talk about that today. And yeah, that’s kind of the elephant in the room. Everybody knows straw management is usually the biggest thing. Trying to get canola established into a lot of residues is a big deal.

Drew Lyon: Yeah. That little seed needs to be placed precisely. It’s harder to do with a lot of residue, isn’t it?

Dr. Clark Neely: Yeah.

Drew Lyon: So, when and where did you conduct these studies?

Dr. Clark Neely: Yeah, so, there’s a lot of set up for these trials. I’ll try to walk the listeners through.

So, this all started way back in 2021. I got some funding from the Washington Oilseed Commission to do this work. And so, I was managing the cereal variety trials at the time, and so we were using those and we would go in ahead of harvest and we would collect some biomass samples, estimate straw yield. And then, we would actually use those straw yield samples to do some decomposition work where we would put residue into a nylon mesh bag and stake it out in the field and let it overwinter and measured whether there were differences in decomposition.

So anyway, we started this using the 2021 winter wheat variety trials that were harvested. And then we would come in in 2022 and we planted the spring canola after that. And we would bulk plant that over the top of where the winter wheat variety trial was. We did that at Pullman in 2022 and we did that at Reardan in 2022.

If our listeners remember, 2021 was like a historic drought year. And so, after I conducted these trials, we weren’t seeing a lot of differences. And I was like, well, you know, we didn’t have a lot of biomass production that year, which may have masked differences that we might have seen otherwise, but by then it was like–this is like a two-year study because you have to do the variety trial and then the canola. But by the time I’d made that decision, we had already missed the window to do it in 2022-23. So, then I got funding to do one more site year using the 2023 winter wheat trials and then following that in 2024 with the spring canola. So, there was a total of three site years.

Drew Lyon: Okay. Where was the last one conducted?

Dr. Clark Neely: Colton.

Drew Lyon: Colton. Okay.

Dr. Clark Neely:  Yeah. And then, so, the Reardan and the Colton sites were both no till and then the Pullman site was a conventional till site. So, those that was the field component.

I also had a lab component. So, the point was, if we do see differences in the field, I want to be able to try to tease apart whether it was allelopathic or whether it was just a physical limitation because of the extra straw.

Drew Lyon: Okay. So, what were your main findings?

Dr. Clark Neely: Right. I’ll start off actually talking about the lab part. So, we took the residue that overwintered and we dried it, ground it. We made different concentrations. We put 1.5, 3, and 6 grams of ground up residue into 100ml of DI water. We let it soak for 24 hours, and then we would take that extract, squirt it on a petri dish with some canola seed and see how that shook out.

After we did that, we didn’t see a lot of differences in overall germination across varieties. In a couple of cases, maybe we saw, like, it took an extra day to germinate, but after three days there were no differences. Everything germinated was between 98 and 100% germination. We did see pretty significant differences across the concentration. So, as you added more residue that did significantly slow down germination. Again, germination was eventually the same, but it slowed it down a day or two.

After four days, we did see a reduction in radical length or the little root length of the seedlings by about 17%. And then we actually measured the seedling biomass from each petri dish after six days, which wasn’t a lot. We did pick up statistical differences, but they weren’t very big. We were talking like 3% differences. And interestingly, even though the different concentrations reduced radical length, we actually saw an increase in biomass. I think that is because, compared to the control which is just DI water, I think that was because we actually were leaching a little bit of nutrients out of the residue that the seedlings were taking up that they didn’t have in just the DI water.

Drew Lyon: Oh, okay. And let me interrupt you, DI water for our listeners is distilled water, correct?

Dr. Clark Neely: Yeah, distilled water.

So anyway, so, the biggest differences were just across the different concentration gradients. Slight differences that we saw in varieties on the seedling biomass, the Stingray CL+ was slightly higher. AP Exceed and Sockeye were slightly lower. But again, these are like minute differences. They were significant but very, very small.

On the radical length, AP Exceed, ARS Crescent tended to be higher. Castella, Blackjack, Shine, Piranha, Sockeye, Voodoo tended to be a little bit shorter. So, that’s what we saw in the lab.

Moving into the field side, which is the more applied side, which is more relevant–and again, going back to the lab, you know, that’s pretty well documented. Like, there’s a lot of studies out there that have documented allelopathic properties, impacts from wheat residue on various crops, so that wasn’t overly surprising.

In the field, we actually—so, of the three site years we had, we had different trials. At Pullman and Reardon in 2021, we had both soft white and hard red winter wheat variety trials. So, we had those trials there. But in 2024, we didn’t have a hard trial. And the soft white trial was split between common and Clearfield/CoAXium. So, in total, there were six trials across three site years, if that makes sense. It’s a lot to keep track of. Six out of those eight, we did detect differences in canopy cover on the spring canola. I wish I could say that they were super consistent across site years, but that wasn’t really the case. I tried to go, like I said, I went through and, like, color coded the tables and tried to pick out trends so that’s what I’m going to mostly talk about are ones that tended to be above average when all site years were below average.

The ones that stood out to me on the canopy cover, ARS Crescent, Castella, Kamiak, TMC M-Press. They all landed in the top statistical group in two out of the three soft white winter trial site years. In the CLOAX, Piranha also did really well. In the hard reds, Battle AX was at the top.

On the opposite end of that, ones that tended to have lower canopy cover included Inspire, Norwest Duet, Rydrych MZ, which is a new WSU release. They tend to produce below average canola canopy. I’m sorry—yeah–below average. And then on the hard red, Canvas, LCS Blackjack, and Missile and WB4311 tend to be below. So, that was the canopy cover.

Looking at straw, ones that tended to produce below average, which I would consider to be good for if you’re trying to establish canola because less residue should make it easier, Castella, Crescent–which are two club wheats–Voodoo, Norwest Tandem, LCS Shine, Hulk, and Blackjack tended to be below average. Ones that tended to produce above average straw included LCS Jefe, Kamiak, Piranha, Resilience, a handful of other ones.

They didn’t all–what you would expect that the ones that tended to have higher straw production would also have lower canopy cover in the subsequent canola. That wasn’t always the case. The Castella and the Crescent, the two club wheats that I mentioned that had below average straw also tended to have better canopy cover. But something like Piranha produced a lot of biomass but somehow still managed to tend to produce higher canopy cover in the spring canola too.

Drew Lyon: Okay.

Dr. Clark Neely: So, some consistent differences that you would expect. Some not so much. So, yeah.

And then I alluded to earlier, we also did the straw decomposition. There was a lot of variability in this data. If I had to do it over again, I’d probably do more replications to try to detect differences. So, what we did–again, we detected differences at most of the site years that we did it, but they weren’t consistent across site years so ones that might have decomposed more in one year or site year might not have done as much in the other.

I went through and tried to pick out trends on the few that were fairly consistent. The ones that stood out to me, again, ARS Crescent, which is a winter club wheat, Cameo another winter club wheat, LCS Jefe, Shine, Norwest Duet, those were in the top statistical group of at least two sites for having higher decomposition, which we would think might be more beneficial. On the opposite end, ones that had very little decomposition, included AP Iliad, Castella, which is a winter club, Pritchett, another winter club, Stingray CL+, Presto, and LCS Jet, which is a hard red.

Yeah. So, that’s where we saw those.

Drew Lyon: Okay. So, you’re looking at it from the standpoint of canola, but there’s also good information there if, say, somebody wants to maintain residue. You have some information on what varieties might be best for that situation. Yeah. Interesting.

So, from a canola establishment standpoint, what are the take home messages or the message that you think you’ve garnered from this research?

Dr. Clark Neely: Well, I think, the main take home is looking at the yield data, which is what I’m going to talk about next.

Drew Lyon: All right. All right.

Dr. Clark Neely: Because that’s what it all boils down to.

Drew Lyon: That is correct.

Dr. Clark Neely: And in this case, I would say actually there was pretty good agreeance that there was no difference, which despite seeing differences in the canopy cover, wheat straw production–in the end, it really didn’t matter. And of the six or eight trials that we had across three site years, only one of those trials trended towards having significant impacts and that was at Colton this past year and our soft white winter trial. The p-value was like 0.13, so it was trending. It wasn’t didn’t meet our bar of 0.05.

So, in that particular case, the ones that tended to be a little bit higher in seed yield were WB1922, which is a new Westbred variety, SY Assure, Castella, which I’ve mentioned that several times as being either towards the top or bottom in some of these categories–those all tended to have the highest yields at Colton. Norwest Tandem, Inspire, LCS Artdeco tended to be towards the bottom in the soft white trial at Colton.

Looking across locations, the ones that trended above average, again Castella across site years tended to have higher spring canola, and LCS Jefe, which is a newer Limagrain variety. And then also AP Exceed and AP Iliad, we only tested those at two of the three site years, but they also trended above average.

On the opposite end, interestingly, Norwest Tandem was the only variety that produced below average yield at all three, which is interesting because Tandem is one of our shorter varieties and similar to kind of like LCS Shine, which you might think people might pick that strictly because of that, because there’s less residue to deal with. But that one trended below average. And then also, Rydrych MZ, which is a new WSU release, only tested at two site years, but that was below average. So, yeah.

So, getting to the take home message again. Some of these growers already know and I think it’s important to highlight canola is amazingly resilient and plastic, so despite seeing differences in canopy cover and some of these other measurements that we took, in the end, we didn’t really see any trends or impacts on canola seed yield, which I think is really important.

The other take home is any differences that we may or may not detect in allelopathy in like lab or controlled settings is usually dwarfed by the physical barrier of the straw. I did some correlations looking at all the data. Regardless of treatment, you know, comparing–I was really interested in just pulling apart and looking regardless of variety, looking at straw yield and like, canopy cover or seed yield. And also, I was interested, you know–growers, we don’t have a lot of data on wheat biomass production but what we do have is a lot of data on plant height on the wheat. So I was like, well, you know, how good is that relationship between plant height in the wheat and the biomass? As you would expect, there is a positive relationship, but it’s not as strong as you might think it is. In one case, I think the r-square value was like 0.5, but in the other two sites only 0.2, so it’s a moderate to maybe only a weak relationship. So, in the absence of any other information, you know, you can go with plant height, but that’s not a great proxy for overall biomass production if that’s what you’re really interested in. So, I thought that was a take home that growers should be aware of. Yeah. So, we didn’t see any relationship between the wheat straw yield and the canola seed yield.

Drew Lyon: Okay. So, canola establishment is one of the challenges of canola production and it sounds like what variety of wheat you follow is probably not the major issue they need to concern themselves with, although it could have some effect in some years. So, what would you have growers focus in on for canola establishment other than what variety they’re following or what wheat variety they’re following in their rotation?

Dr. Clark Neely: Well, it’s not terribly sexy, but I would just say keep doing what you’re probably already doing, which is good residue management and having good planting equipment that can handle whatever residue that you’re dealing with. I think that by far and away is probably going to be the biggest thing that you need to focus on with canola production, which most growers already know that. [laughter]

Drew Lyon: All right. Well, but it’s good to know because I know those questions were out there and it seems that it’s not as big an issue as maybe some people have felt it is, which is good information to have.

Dr. Clark Neely: Right.

Drew Lyon: So, Clark, thanks for being my guest today and discussing this research you’ve done on canola emergence following wheat varieties. I think our listeners will find it of interest.

Dr. Clark Neely: I hope so.

Drew Lyon:

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Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcast app. If you have questions or topics you’d like to hear on future episodes, please email me at drew.lyon — that’s lyon@wsu.edu — (drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu and on Facebook and Twitter [X] @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.

I’m Drew Lyon, we’ll see you next time.

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