Advantages of Seed Size and Seeding Rate with Dr. Clark Neely

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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 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, can you explain to the listeners what type of work you’ve been doing in seed size and seeding rates in wheat? I know that’s an issue that often comes up when speaking with growers is, you know, what rate should I be planting at? And do I base it on pounds or do I base it on number of seeds? So, what have you been doing to address that question for growers?

Dr. Clark Neely: Sure. Well, I’ll go back and just kind of give you a recap overview of all the treatments and trials that I have done last few years. So, a lot of the work that I did revolving around seed size and seeding rate came from just having some extra space to burn in the variety trials and trying to put that extra space to good use. So, a lot of it started out as just adding some treatments in, that started out in 2022, had some extra space so I threw in some seeding rate treatments in the hard red winter trials. Then in 2023 started looking at the seed size. Had some seed size treatments in the low rainfall zone for the winter wheat trials with LCS Shine. That was 2023. This past year, in 2024, didn’t have room in the low rainfall, but I also wanted to look at the high rainfall, so we had some treatments in the winter wheat variety trials there. So, on the winter wheat side, that’s where we have treatments for seed size.

On the spring wheat side, I’ve done seed size treatments in the embedded inside the variety trials the last two years, so 2023 and 2024. And then also did some dedicated trialing just for seeding rate with spring wheat the last two years as well.

So, the seed size [for] spring wheat, we’ve done basically anywhere that we did variety testing. On the seeding rate side, we had trials at–tried to cover the spread, so we had a trial at Horse Heaven, Reardan, St. John, and Farmington. So, tried to get a broad range of environments there and did that across two years.

And then, most recently I had got some funding to do some dedicated trialing looking at interactions between seed size, seeding rate, [and] variety. So, in 2024, I had three locations for winter wheat and had one location for spring wheat. So, it’s kind of all the different trials and treatments that I’ve had.

Drew Lyon: Okay. There’s a lot of potential interaction there between location, seed size, seeding rate, and what was the other one?

Dr. Clark Neely: Variety.

Drew Lyon: Variety. Yeah. So, that can get a little complex. You came on the show about a year ago, I think, and talked about your results from 2023. Learn anything new from 2024 data?

Dr. Clark Neely: Sure. You know, I was kind of sweating it because you never know. You know, a lot of the trends were really nice and consistent in 2023. And, you know, more data is always better and you like to see, like, consistent differences. And so, I was really worried, you know, well, maybe things will be completely different or we don’t see any differences in 2024.

I would say though on the spring wheat seed size, I think the results are still very consistent with what we saw in 2023. We still saw advantages in stand counts, advantages in canopy cover, advantages in yield.

Drew Lyon: With larger seed than smaller?

Dr. Clark Neely: Yes. Yeah. Thanks for clarifying. Yeah. Larger seed was making a positive impact on all three of those characteristics. So, just to recap, the seed size for spring wheat in 2023, we saw about an increase of about two plants per square foot, which was roughly about a 10% increase in stand.

Canopy cover, we took that, like, advantageously, like, whenever we were at the trials so the timing of that varied dramatically from one location to another. On average, it increased 5%. But keep in mind that some of those times that we took [the measurements], the plants were still very, very small, so it would have been very difficult to see differences. In some cases, though, I think the biggest difference we saw at Lamont in 2023, we saw like a 73% increase in canopy.

So, there were definitely some locations, especially when you took it later in the season, the differences were more dramatic.

And then on the yield side, we didn’t see a big difference from our small and medium. By going from the medium to large seed, we saw about a four bushel per acre increase on average. And for perspective, I think the seed size was roughly about 13,000 seeds per pound on the medium. And, I want to say it was about 8,000 maybe on the large.

So then looking at 2024, again, we saw similar differences. I still don’t have all the data analyzed, but as far as yield goes, the bump wasn’t as dramatic, but it was still significant–and it was about two bushels per acre on average across all the locations. And it also occurred going from that 13,000 seeds per pound to the next biggest seed. So, to me, the data was kind of suggesting that maybe there’s a threshold there around that 13,000 seeds per pound. At least that’s what the data was saying anyway.

I only have a couple years of data on the canopy cover, but the two locations that I had summarized, the average increase was about 36% on canopy cover. And then we also saw about a 10% bump in stand as well.

Drew Lyon: Okay. You know, as a weed scientist, when I go out and talk about general management practices for managing for weeds, one of the suggestions is use larger seed and plant it shallow so it comes up and competes and puts up a canopy more quickly. So, it might be something you might want to look at sometime is just, you know, not only just how does it affect yield, but how does it affect the plant’s ability to compete with weeds when you use large seed versus a smaller seed or use a higher seeding rate versus a lower seeding rate?

So, just throwing you a little idea there in case you ever want to add yet another thing to measure in the field.

Dr. Clark Neely: Right. Yeah.

Drew Lyon: So, what are some of the main points of this research, do you think? What are the points you’d like to make to growers about seeding rate, seed size? And, I guess another question that just popped in my head is can growers make a purchase decision based on seed size? Can they ask what the seed size is or go shopping around for larger seed or smaller seed of a variety?

Dr. Clark Neely: Yeah, that’s a good question. So, number one whenever I’m presenting this information I always highlight and emphasize that I still think variety selection is the number one priority, so make sure you get a variety that you know does well in your area and will perform well for you and meet your needs.

Number two, I mean, growers may not always have an option; maybe they only have one source for a variety. But, if you do have an option to go somewhere else, sure, you could, look at the certified seed tags and seed companies or distributors should have that information. You should be able to tell which one has larger seed.

You could, if you–let’s say you don’t have an option, you only–you know what variety you want to plant. It’s a little bit smaller than you would prefer. You know, you could always potentially adjust your seeding rate, which was–we didn’t really get to that earlier in the conversation–but, some of the new trials I had going on in 2024 where we had different treatment combinations of seed size, seed rate, and variety was kind of geared towards answering that question [of] “Okay, you know, you’ve got smaller seed. Can you compensate by adjusting your seeding rate?”

Kind of the nutshell of the results from that was, I would say: In general, yes, bumping up your seeding rate can adjust or improve your stand. I think the data suggested that. What I don’t know that it did really strongly suggest was by even adjusting that we really didn’t see an adjustment in yield. Larger seed always seemed to make higher yields. But, you know, that gets complicated and tricky because I feel like when we were planting these trials back in fall 2023, overall, we had really good planting conditions so the seed wasn’t really tested, you know, so to speak. It had favorable conditions.

I do feel like maybe if you had more adverse seeding conditions, poor moisture, poor seed soil contact, maybe then you would start to see differences not only in stand, but then also in yield. I think probably just what happened was in most cases we had sufficient stands and we had favorable conditions where plants could tiller out, compensate. So, I think that’s the take home there.

Drew Lyon: Okay. I know your studies–or at least I don’t think your studies were set up to really investigate this–but, you know, winter wheat has the capacity to tiller more than spring wheat so I wonder whether does seeding rate make a bigger difference? [Would] increasing seeding rate make a bigger difference in spring wheat, [do] you think, than in winter wheat because of that lack of tillering and spring wheat compared to winter wheat?

Dr. Clark Neely: Also a good question. And, I was kind of trying to answer that in those trials. So, we had three winter trial locations for that trial I just mentioned with seed size, seed rate, variety, and then we also had one–those were, just for the audience’s reference, those were conducted at Ritzville, Douglas, and Creston. The spring wheat trial was located at Lind.

And yeah, we did see differences for variety, for seed size, and for seeding rate in the spring trial. Those differences are pretty small. They were significant, but they were pretty small. That’s not surprising, because it’s Lind and our yield topped out at like 20 or 25 bushels.

So, the biggest difference in yield at Lind was due to variety. We saw about a three-bushel difference between Chet yielding about three bushels more than the WB9668. We saw about a two-bushel advantage from the seed size going from small to large. I did see a difference from the seeding rates on the spring wheat trial and those range from–the low rate was 600,000 seeds per acre, we had one at 750,000, and the highest was at 900,000 seeds per acre.

Drew Lyon: Okay.

Dr. Clark Neely: So, probably–I haven’t done the economics on that. From an economics, strictly speaking, like, paying that much more for the extra seed at planting probably wouldn’t cover the extra bushel. But it’s nice to know, if you do get that advantage for better canopy cover and weed competition–it’s nice to know if that’s one of your major goals, you could bump up your rate and at least maybe offset some of the extra costs and certainly not lose any yield by doing that.

Drew Lyon: Okay. So, are you going to continue the study into 2025, and if so, [are there] any changes you’re going to try or what’s the future of the seeding rate, seed size work that you’re doing?

Dr. Clark Neely: I’m pretty much wrapping it up and I really just want to repeat the spring wheat seed rate, seed size, variety combination trial one more year at Lind. And then I think that’s going to wrap up most of what I’ve been working on.

Drew Lyon: Okay. And then will this come out as a recommendation then in an Extension guide or a tool or something?

Dr. Clark Neely: That is my goal, yeah, [for it to] come out in an Extension bulletin or publication at some point.

Drew Lyon: Okay. Very good.

Well, Clark, thanks for coming on the show and updating us on this research. I think it’s, like I say, it’s a question I hear quite often. So, I know growers are interested in it and I’m sure they’ll be looking to see what kind of recommendations come from your work.

Dr. Clark Neely: Okay. Thanks, Drew.

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