Intercropping on the Palouse with Dr. Garett Heineck

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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. Garett Heineck. Garett is a USDA-ARS cropping systems agronomist in the Northwest Sustainable Agroecosystems Research Unit and is stationed in Prosser, Washington. His agronomic research and expertise help support a diverse team of ARS researchers working together to improve the sustainability and profitability of agroecosystems throughout the PNW dryland region. Hello, Garett.

Dr. Garett Heineck: Good to be back on the show. Drew.

Drew Lyon: Hi. Good to have you. You’re always doing some interesting and innovative work, so I like to get caught up with you every once in a while. You’ve mentioned in previous episodes that you’ve been working on intercropping in the Palouse. Can you give us an update on that project?

Dr. Garett Heineck: Yes. I think it was about two years ago or so that when I first was on the show, I had described a project. It was shortly before Isaac Madsen actually left and he was just describing his last work that he had done on peaola or peas and canola being grown in an intercrop together. Since then, the project, it really has taken off. And this intercropping project is graduate student led, by a student, Katie Smith. Perhaps she’ll be even on the show one of these days.

Drew Lyon: Yes, we’ll love to have her.

Dr. Garett Heineck: So, we just completed a three-year study, and like you said, it is in the Palouse and it is on intercropping. We focused on intercropping peas and canola and chickpeas and canola, so this is our peaola and, I think, garbola, we can call it. So, yeah, that’s a fun name to say and listen to. And the premise was, spring crops, right, because we’re in the Palouse. And we also wanted to follow our intercrops with winter wheat to see if there [were] any effects that the intercrops or sole crops–being the canola, the peas, and the chickpeas–what those might do to the following wheat crop. There have been some reports, mostly from the drier parts of eastern Washington, of canola potentially reducing yields of the following wheat crop. So, we wanted to investigate that as well.

So, this has got both agronomics and soil microbiology involved in the project. I am focusing on the agronomy portion as the agronomist, and Katie, the soil science expert, is focusing on the soil science side. So, I think between the two of us, we’ve got some pretty interesting results and I’m really excited to share those with you today.

Drew Lyon: Okay. So, intercropping is growing both crops together in the same field. To measure, to compare that are you comparing it to each crop grown individually, and if so, did you find some difference between whether–in other words, did they yield more when you grow them together than when you grow them separately? Or what did you find?

Dr. Garett Heineck: Oh, yes.Let me paint this picture for you, Drew.

Drew Lyon: All right.

Dr. Garett Heineck: So, Isaac used to talk about overyielding or the land-equivalency ratio. And that’s calculated by comparing your intercrop with your–I’m calling them sole crops. It’s like a monoculture but just sole crop: chickpea, pea, or canola. If you envision two acres of land: the first acre’s got let’s say canola on it and the second acre’s got peas on it, grown individually. Say their total yield is 1X.

Now, let’s say we take another piece of land, two acres in total, but we grow all of it in peaola, peas and canola. Let’s say we get 1.1X or 1.5X, which is what Isaac was finding in winter peola. That would be called overyielding. So, the same amount of ground, but we’re yielding more in the intercrop than the sole crop. And that’s the land-equivalency ratio. And when the value is over one, we call that overyielding.

So, I can tell you a little bit about what I found if you want.

Drew Lyon: Yes. That’s that was going to be my next question. Yes. What did you find?

Dr. Garett Heineck: So, although our results didn’t suggest an overyielding to the extent that Isaac found in his winter crops, it was more in line with what he found in his spring trial, which I think was done, I think it was done in Colfax or Dusty, somewhere in that region. And we were getting overyielding estimates between 1.1 and 1.2, so maybe at most 20% higher than the sole crop or the monocrop yield, which is still promising and it was significant. And so, we were really excited to see that.

Also, something interesting to note, because I’m such a cropping systems nerd, I wanted to see which crops were dominant in the mix. Was it canola? Was it the peas? Was it the canola? Was it the chickpeas or the garbs? And you can plot this on a graph–this is going to be harder to paint, so I’ll just tell you that generally speaking, because we had only one ratio in our seeding in this trial, that our canola was far more dominant than the chickpeas or garbs. And the peas were actually slightly more dominant than the canola in the peaola, which is what Isaac also found to a certain extent.

And I think this might actually be the first time that someone’s tried garbola, the chickpeas in canola, so it certainly was interesting to see that. And I can go into that a little bit more if you want me to.

Drew Lyon: Well, you know, just in my work in weed science, I’ve noticed that peas are much more competitive with weeds than chickpeas are with weeds, and so that doesn’t surprise me that it’s probably–in competition with another crop, it might be a little better competitor than chickpea would be. So, that kind of fits my [own experience].

Why don’t you go into a little more detail? And, I guess, another question I have for you: so, I did some oat-pea mixtures work when I was in Nebraska, and you can play around with that ratio of how much oat and pea. So, if you wanted more biomass, you planted more oats and less peas, and if you wanted higher quality, you planted more peas than oats. Do you see something happening, some possibilities here with canola and peas or canola and garbs?

Dr. Garett Heineck:  I really enjoyed working with chickpeas. I’m a little biased there. I do like peas. I like peas, but the chickpeas, they’re very fun to grow. Just the way they grow and their harvestability and [they’re] much easier to walk through as well than the pea crop. Like you said, it’s a much more competitive crop and what the chickpeas tend to, what the garbs tend to do is they change actually their yield components. These are the components of the plant that make up grain legume yield. For example, the number of stems, the number of pods, and the number of seeds per pod make up the components in chickpeas.

And what chickpeas did is they elongated more; the plant got taller inside of the canola crop and it branched far less. They had far fewer branches then those chickpeas grown as a monoculture, as a sole crop.

This was not seen in the peas. The peas, as a more aggressive species, like you said, actually wound themselves around the canola. In our second year in 2023, I actually have some interesting pictures where the tendrils of the peas actually completely encapsulated some of the canola pods. And I think that actually led to some reductions in yield, and probably is why we saw a lack of dominance in the canola.

So, as these yield components shift, that really gives some interesting insight into, like you said, maybe we can plant instead of doing a two-thirds rate of chickpeas like I did, and a half rate of canola, maybe we could go up to a full rate of chickpeas or perhaps even higher because the yield components change and there’s actually more room per chickpea plant than there would be in a monoculture stand in.

Drew Lyon: Interesting. Yeah, that whole ratio thing is–what about, I know chickpeas the size of the pea is pretty important. Did you measure seed weight or seed size in the chickpeas?

Dr. Garett Heineck: Thanks for asking, Drew. I sure did. Yes, we saw some differences amongst seed size and we also measured grain quality. That’s been reported in the literature, and I was like, “Ah, people will be really interested to see what’s actually going on with that.” Generally speaking, we didn’t see any major differences in the seed size. Some small differences, but nothing that I would really write home about. And that was encouraging.

The number of seeds per pod and the size of those seeds wasn’t necessarily impacted to a high degree in the intercrops. The canola actually had larger seeds in the intercrop because there were fewer canola plants, right? Half rate versus one rate. And especially in the chickpeas, right? The chickpeas are so small and noncompetitive, the canola was able to get much larger. And the yield components must have compensated through increasing the size of the seed in canola.

So, when we looked actually at the quality of the grain, the protein content of the grain legumes and the oil content of the canola, we were looking to see if things were changing. For example, did our protein content decrease dramatically or did our oil content decrease dramatically? And neither of those really changed all that much. We’ve seen in the literature actually that protein can go up in a pea crop and we saw slight increases in protein. But again, nothing I would write home about or nothing that I would say, ”Oh, we need to stop and think about this as a serious problem.” So, I was also really happy to see those numbers come out as well.

Drew Lyon: Okay. I guess an area that I’m really curious about is water use between monocrop and this intercrop. I know, when I was in Nebraska, there was a big push that if you planted a cover crop that contained ten species–I forget, what nine, ten species–it used less water than if you planted a monocrop.

I didn’t really believe that. [I] did some research that would suggest maybe that isn’t true, but now I’ll find out if it’s true here or not. So, did you find different water use between intercrop and monocrop.

Dr. Garett Heineck: Yeah. So, actually I read that study, Drew. That was an interesting project that you did with the cover crop, because I did a similar thing in this study where we had neutron access tubes. So, these are big, long aluminum tubes that gets stuck down in the ground, in this case about 4.5 ft. And we stick a radioactive source down in there called a neutron moisture meter and it emits fast neutrons. And as those neutrons interact with water molecules, they get returned as slow neutrons, and that is directly related to volumetric water content. And you can then measure water deep down in the soil, which is pretty handy.

What we found was and this is actually pretty interesting–besides the fact that I had a great time analyzing this data, I’ve never worked with soil moisture data before, so it was fun to do that. But what we found was, as you might expect, the peas did not take a lot of water from deep in the soil profile. In the surface 70 cm, or that would be about two feet, a little over two feet–so I’ll speak in feet here. So, a little over two feet–they took about the same amount of water as everything else as the chickpeas in the canola.

The chickpeas took the most water, which is, I think, not surprising to anyone who’s grown chickpeas. They can hold on for a very long time and keep drawing water. However, they all ran out of water about the same time.

Deeper in the profile, things started to change. Our canola and our chickpeas were able to draw water far deeper, down to 130 cm, draw it longer, and actually draw it down far lower. And so, when we start looking at our intercrops versus our sole crops, if you envisioned a graph with time on the x axis, on that horizontal axis, and water use, water being used on the up and down the vertical y axis, you’d see a sharp decline in water use. And then as the soil dries out, you start to see a break in how much water is being used.

Peas, that happens first. They kind of give up and they stop using water. Whereas, the canola and the chickpeas keep using that water and they keep drawing down that water in the profile. And things like canola will just keep drawing it. Chickpeas not quite as much. And down at 130 cm, which is about four feet, but they do draw quite a bit more than I thought they would.

But that is an interesting point, because we use a lot more of our water in this annual cropping region of the Palouse, and we should use it because it gets recharged annually, when we start mixing in things like canola with our peas. So that was fun to see. And I’m glad we saw those interesting results.

Drew Lyon: So, actually your water-use efficiency then would be greater with the intercrop than it would be with a sole crop, is that correct?

Dr. Garett Heineck: Yes. Yeah. It should be greater because you’re getting higher yields and you’re pulling more water from deeper in the profile.

Drew Lyon: Okay. So then, that might influence how the next winter wheat crop would do. What did you find there? Did the winter wheat crop perform differently after intercropping than sole cropping?

Dr. Garett Heineck: Yeah. One of the big things I always try to incorporate into the research– because I work on a lot of wacky stuff, right, Drew? I mean peola is and garbola is not that bad, but a lot of my stuff, it’s on the fringe here. So, I’m like, “Well, let’s tie it back into what people are making all their money on.”

And so, when we measured the following wheat crop, interestingly enough–so a little bit about what I did, I didn’t shoot for the big 150 bushel winter wheat crop. I actually shot for a very low yield about 75 bushel. So, I used, the great calculator that we have online for calculating nitrogen. And I shot for about 75 bushel of winter wheat.

That was to draw out any effect from the grain legumes. And what I found was is we seem to have an awful lot of nitrogen in our soil profile as it is, so I didn’t have to fertilize at all. But even so, I saw no effect on yield from any of the sole crops or intercrops. I didn’t see any effect on any yield components in the wheat. I didn’t see—almost I saw no effect on grain size. So, that was very interesting and quite encouraging, I think, to see.

Now, I would say that when we looked at grain quality, the wheat quality, there was an effect of that grain legume. The peas especially increased protein, percent protein in the winter wheat, which I think would suggest that we were getting some nitrogen credit benefit from the pulse crops.

Drew Lyon: Right. Did you measure soil water in the wheat crop as well so you know whether the profile got pretty much filled over the winter time or not?

Dr. Garett Heineck: That’s a great question. And I did not do that. No. I didn’t sink neutron access tubes in the second year of the rotation.

Drew Lyon: But the fact that you didn’t see any, even though the canola and garbs were able to extract more water from the soil that didn’t show up in the following wheat crop so that would suggest that precipitation over the winter probably refilled the soil profile.

Dr. Garett Heineck: Yeah, I think that’s what it would suggest. That’s what–if I was going to make a guess, I would probably kind of count it in that there wasn’t too much of an impact on soil water deep in the profile from our previous crop. Certainly not enough to make a difference statistically in yields.

What might be interesting though in the future is actually, as the student, Katie, as she comes out with her results on the actual microbiological portion of this work, what actually happened with the soil microbiota?

And there could be lingering effects that were just overridden, perhaps by the amount of nitrogen that was left over. Or who knows what? But it would be interesting–it will be interesting to see those results, both in the intercrop and in the following crop.

Drew Lyon: Okay. So, what [does] the future of this research look like and what other data might be coming out of it?

Dr. Garett Heineck: Thanks for asking. There is a brand new study coming out. And we already actually got through our first season. It’s not in the Palouse, but it is at Wilke Farm, so Aaron Esser is hosting it. It’s led by Shikha Singh. She’s at the Lind dryland farm and she actually has a more elegant design, I should say, than Katie’s and I’s design, where there is multiple nitrogen treatments and there is multiple ratios of pea and canola–there’s no chickpea in canola; it’s just peola. But I’m really excited to see how that turns out and we’re just getting that data in, so hopefully, you know, the data is going to keep coming out here, Drew. There’s more to the story.

Drew Lyon: All right. It’s very interesting work. Is there a place the listeners can go to see what you’re up to and what you’re finding?

Dr. Garett Heineck: For this particular study, we’ll be getting numbers out here officially probably in the next couple of months, so this will be published and that will be an open access journal article. But if the listeners don’t feel like digging through Google Scholar, I’m hoping we can probably put this up on our Cook Agronomy Farm LTAR webpage and that can be put in the show notes, I suspect.

Drew Lyon: Okay. Yes, we can get that added.

Dr. Garett Heineck: Awesome. And we will begin to disseminate that knowledge through that website.

Drew Lyon: All right. Thank you, Garett. Always interesting to hear what you’re up to and what you’re finding. Hope to have you back on next year to tell us what new, interesting studies you’re looking at out in the dry lands of eastern Washington.

Dr. Garett Heineck: Oh, absolutely, Drew. We’ve got–this is a spoiler alert–I hope I have some time here. Yeah, we’ve got some new interesting data coming out on the Kernza, the perennial grains front, so I hope to be back to share some of that.

Drew Lyon: Excellent. Thank you, Garett.

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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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The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.