How Bad is Soil Compaction for Crop Growth? with Natalie Sturm

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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 Natalie Sturm. Natalie is a soil science Ph.D. student in Dr. Haly Neely’s Applied Soil Physics Lab at WSU. Before starting her program at WSU, Natalie earned a bachelor’s degree in agroecology from Montana State University and a master’s degree in agronomy from South Dakota State University. During her master’s, she quantified the differences in soil health properties between several long-term no-till crop rotations under the advisement of Dr. Duane Beck. Now, Natalie is excited to learn more about agriculture across the Pacific Northwest and to apply cropping systems principles to solve soil management challenges. Hello, Natalie.

Natalie Sturm: Hi, Drew.

Drew Lyon: So welcome to the WSU Wheat Beat podcast. I wonder if you can tell us some of those soil management challenges that you in the Neely Soils Lab are trying to address.

Natalie Sturm: Yeah. Yeah, for sure. So we are a soil physics lab, so we deal with all of those physical properties that relate to soil. So things like water movement and retention, erosion, and then our big one right now is soil compaction. So we have a large field-scale soil compaction research project that we’re working on to try to work on measuring soil compaction, defining what does soil compaction do to soil function and crop growth, and then what can we do about soil compaction in terms of management?

Drew Lyon: Okay. Well, you know, soil compaction is a fairly ubiquitous problem in production agriculture. Are there any common misconceptions about soil compaction?

Natalie Sturm: Yeah, Yeah. So like you said, it’s pretty widespread in production agriculture simply because we use really large and really heavy equipment on our fields. And so we’re never going to totally avoid compaction, but the hope is maybe we can try to kind of minimize it.

I think some of the main misconceptions come from just kind of our lack of knowledge around compaction. There’s a lot of unknowns. For example, how bad truly is soil compaction for crop growth and eventually crop yield? You know, you hear these numbers like, “oh, 40 percent yield drag in a compacted soil.” I have yet to find that number actually anywhere in the research literature.

And so there’s a lot of work to be done in terms of how bad is compaction for crop growth. Some growers that I talk to say, “oh, I really notice it and I want to do something about it because I think it’s hurting me economically.” And other folks say “compaction, that doesn’t matter.” So that’s kind of a big unknown.

I think some of the other misconceptions have to do with how to manage compaction or what’s causing it. So I’ll talk to some growers who say, “oh, I deep-ripped that field 20 years ago and I’ve never had compaction ever again.” Whereas other growers just say, “well, ever since I switched to no till my compaction issues have gone away.” So there’s kind of a lot of sort of gray area about like what really is causing compaction and what systems make compaction worse. And so there’s a lot of room to figure out what’s going on there.

Drew Lyon: Okay. And I know way back when I was at Nebraska, we did some soil compaction work with sunflowers and sorghum and dry land corn, trying to figure out which crop was affected more by it. And I remember one of the difficulties I had was we had one of these probes you stick in the soil and just operating those is kind of interesting. And then depending on the soil moisture level, all those changes. So we hear soil compaction, but it’s not so easy to measure.

Natalie Sturm: Right. And that’s part of what we’re working on is how do you measure it? Because like you said, up until recently, it’s been very person dependent. So who’s pushing that hand probe into the ground and what does that really mean? So we actually have a hydraulically mounted soil penetrometer that we’re using for our field-scale compaction measurements. And it basically measures the force that it takes to drive that penetrometer into the ground. And that gives us a little bit better reading that’s not so user dependent, because it is hydraulically operated. And so we’re really excited about that tool and that’ll hopefully be really helpful.

Drew Lyon: That reminds me of going out to a field one time with a gentleman who was much larger than I was and he was able to push it and I was jumping on it and I couldn’t get it. So what are some of the contributions you’re making to the Neely Soils Lab in terms of compaction?

Natalie Sturm: Yeah, Yeah. So as I mentioned, I have some other colleagues in the lab working on that penetrometer to better measure compaction.

Another colleague is working on those crop yield impacts. And then my role is to say, “okay, there’s compaction. What do we do about it? How can we manage it? And what would be some ways to deal with that compaction once it’s there?” And then I’m also hoping to kind of gauge farmer perceptions, as well, to see how widespread is compaction in Washington and even nationwide with some of my research and to see, you know, is this something that farmers are concerned about, something that they want to manage? And if so, what would they like to see be done from the research side of things to manage that compaction?

One of the ways that I’m doing that is through focus groups. We’re calling them soil compaction think tanks, where I’m gathering groups of farmers all across Washington state, as well as Texas and Wisconsin. And I am basically doing kind of this guided-discussion format where growers and I just kind of have this back and forth about how bad is soil compaction right now. Do they want to do anything about it? What can I, as a researcher, do for them to help come up with some better management techniques? So that’s been pretty exciting to get to work on.

Drew Lyon: Okay. If a grower is interested in becoming or attending one of these focus groups, how would they go about doing that?

Natalie Sturm: Yeah. So we have been going through mostly county Extension agents. So I would say if you’re interested in attending a focus group, be on the lookout for any, you know, sort of advertisement or emails or phone calls from your local county agent and be ready for a focus group coming to your county soon.

Drew Lyon: All right. Very good.

What will you do with the information after you complete the focus groups? And I’m also kind of curious whether you expect to hear different things from people not even within–if you’re going across the state of Washington, eastern versus western–and then Texas and Wisconsin.

Natalie Sturm: Yeah. Yeah. So we are and that’s kind of the reason why we’re doing this over such a broad range is we’re really curious to say does rainfall, soil type, and cropping system, does that impact the level of concern that growers have for soil compaction, as well as the prevalence of that soil compaction? And so I do expect to see some differences in terms of the levels of concern and just the levels of compaction across those different regions.

I’m also really interested to see what different ideas for management come up across these different regions, because I do think somebody, you know, in the Ritzville area is probably going to have some different ideas of things they’d be willing to try on their farm compared to somebody from, you know, Wisconsin–might be a little bit different. So that’ll be really interesting to see those differences.

In terms of what I’ll be doing with the information that I’ve gathered, again, I’m really trying to make my research as relevant and applicable and as useful as possible for growers. So I hope to take any of their ideas or concerns and kind of build that into our research program and then disseminate those results back to those same growers and say, “look, you were curious about compost or gypsum applications. I ran this trial and this is what I found.” So kind of trying to have that sort of, you know, cyclical approach to research.

Drew Lyon: Okay, cool. So what other projects are you working on to study how compaction affects management?

Natalie Sturm: Yeah, Yeah. So in addition to those focus groups and then any, you know, application trials that come from that in terms of like compost or liming, I’m also doing a crop-type sequence trial. So looking at the order in which we plant different crop types, specifically thinking about their root systems.

So grass crops have fibrous roots, broadleaf crops have tap roots. Our question is in a compacted setting, is it better to say plant that taproot first and maybe try to break through a hard pan and then come in with a fibrous rooting system? Or maybe that fibrous rooting system–maybe it’s better able to find small cracks in that hard pan. Break it up a little bit and then come in with a taproot.

This kind of came about because you hear a lot about like Tillage Radish is really good and canola is great, but then you go out into a field setting and I’ve seen Tillage Radishes that are like above the ground–they don’t even make it through that hard pan. And so there’s a lot of questions regarding which crops really are best if you want to go the cropping route to try to manage compaction.

Drew Lyon: I remember in western Nebraska going out into some sunflower fields and sunflowers are–you know, supposed to have a strong taproot–and you dig down and that root hit the hard pan and it just went sideways– but it never did go through that hard patch. So, that’s a good question. So what would you tell a farmer who’s concerned about soil compaction on their farm?

Natalie Sturm: Yeah. Yeah. So the way I like to think of it is the best way to manage soil compaction is to avoid soil compaction in the first place. It’s really hard to get rid of compaction once you’ve got it. So as difficult as this is to say–you know, easier said than done–avoiding driving on really wet soil is kind of the key. Sometimes we don’t have a choice. You know, we got to get into the field when we can get in. But avoiding those driving on wet soils as much as possible really is kind of the key.

Drew Lyon: All right. Well, thank you, Natalie. Is there is there a place that people can go to find your research? Does the Neely Lab have a website where they post these things?

Natalie Sturm: We don’t have a website currently. I’m hoping to publish some Extension publications. For sure, from the results of those focus groups to kind of give a regional and nationwide picture of what’s going on with soil compaction and then as well as some Extension and other publications about the results from those management trials.

Drew Lyon: All right. Well, thank you for being my guest today. I think soil compaction is an issue that often gets overlooked and yet probably robs at least some yield from many fields throughout the country, really. So very interested to hear how your results turn out here in a year or two. And again, thanks for joining me.

Natalie Sturm: Yeah, thanks so much for having me.

Drew Lyon: 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 @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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