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Stubble Height and the Soil Water Story with Dr. Bill Schillinger

Posted by Blythe Howell | September 7, 2021

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Fig. 1. The stubble height treatments imposed in the experiment were: (a) short (3 in.), (b) medium (10 in., foreground), and (c) tall (, right). An additional treatment of mowing tall stubble in mid-June (c, left) was included in 2018 and 2019.


Episode Transcription:

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 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 Dr. Bill Schillinger. Bill is WSU’s dryland cropping systems agronomist. He is based at the WSU Lind Dryland Research Station. Bill conducts Long-Term Cropping Systems field experiments and also short duration field and laboratory studies. Prior to joining WSU, Bill worked in agricultural development projects for 10 years in Asia and Africa with the U.S. Peace Corps and the U.S. Agency for International Development. He has also conducted numerous short term consultancies around the world for the World Bank, USAID, and the Food and Agriculture Organization of the United Nations. Hello, Bill.

Dr. Bill Schillinger: Hi, Drew.

Drew Lyon: So, Bill, today we want to discuss some work you recently finished up on winter wheat, stubble, height effects and soil water capture and retention during long-term fallow, which is a topic in a year like this that is really of a great deal of interest and importance, I’m sure. Can you tell us a little bit about the study and what the objectives were and why you think the research is important?

Dr. Bill Schillinger: Sure. Well, this was a four year study conducted near Ritzville, Washington, on Derek Schafer’s farm. Derek and a couple other area farmers had purchased stripper headers for their combine’s. Stripper headers are rotating or they have rotating motors with eight rows of fingers that strip off the wheat heads and leave just or essentially the entire plant stand or plant stem standing and anchored to the ground. So we were interested in what affect the tall stubble would have on water storage in the soil over winter, as well as evaporation of the soil water during the hot, dry summer months that precede winter wheat seeding and by long fallow I mean, the typical 13-month fallow period between harvest of winter wheat in late July. And then taking it through the next year to the late August, right before seeding wheat, that’s 13 months. We were also interested, interested in what effects tall stubble would have on soil temperature during the hot June through August period at the end to follow and how this might tie into soil water into the soil of water story. So Derek and I would select a good location each year over the four years. And this was a different location on his farm each year, obviously. It’s wheat fallow so we had to move it around and he would harvest here with a stripper header, record the grain yield, and then we would come in with our Lind station commercial combine with a conventional header and cut it at two heights, either 10 inches, which is fairly typical for what farmers do, and the other one, we shaped it as close to the ground as possible. And so we ended up with three stubble height treatments. The tall stubble, again, that’s just clipping the heads off the wheat with 30 inches tall on average. And then we had the ten-inch stubble and the shade ground ended up with about three inches of stubble. And we had four replicates of all treatments. And importantly, this was chem-fallow. So there was no tillage done during the entire fallow and weeds were controlled with herbicides.

Drew Lyon: Okay, so you have these three different stubble heights and four different years. What measurements did you take in these studies?

Dr. Bill Schillinger: Well, right after we’d harvest, which is, of course, the beginning of fallow, we measured soil volumetric water content in all the plants in six inch increments to adapt the six feet. And we did the same thing in early April to measure the overwinter precipitation capture in the soil. And again, at the end to fallow right before Derek seeded the next crop. And additionally, we also measured seeds on volumetric water content in one-inch increments to a depth of 13 inches right before Derek planted wheat. And then for soil temperature, my co-investigator, Stewart Wuest, we worked with the USDA Agricultural Research Service in Pendleton, Oregon. He installed soil temperature sensors in the treatments for from the near surface all the way down to 16 inches below the surface. And these sensors recorded soil temperature every five minutes. So he again, he installed these in mid-June and left them in the ground until the end of August.

Drew Lyon: Okay, so that’s a lot of data actually that you collected from these these plots.

Dr. Bill Schillinger: Yeah, quite a bit.

Drew Lyon: Okay. So after you collected all of that and took a look at it, what what were your key findings from the work?

Dr. Bill Schillinger: Well, our findings varied by year, depending on the type of winter weather we had and the amount of stubble that we started off with was that was also important. And during these four years, our starting point for stubble or Derek’s wheat grain yield that ranged from 28 bushels to 90 bushels per acre, and the four year average for that was sixty two bushels per acre. So we had one drought year and three really good years. And then the so the starting residue level during the four years ranged all the way from 2300 pounds per acre to 7600 pounds per acre. And you know, and after the bad crop the first year, we measured no differences in overwinter water storage and in the soil at all. It was an open winter and very little snow. However, the next year, there was lots of stubble and lots of snow. And in that year, the tall and medium stubble had way more soil water in April than the short stubble. And the same thing, again, happened in the winter of 2019 when there was a lots of drifting snow. So however, when we did the final soil moisture measurements at the end of fallow, we found that way more water had evaporated from the tall and medium stubble than from the short stubble. In the most over summer, water loss was in the tall stubble. And that really surprised us. The short stubble had the entire surface covered with flattened stubble, which really made a difference. So after the second year, again, the second year was that big winter with with a lot of snow where we found those huge differences. We put our heads together and said, well, maybe the best management practice is to leave the residue stall– tall during the winter and then mow it before the weather gets hot. And so for the final two years, we added that treatment mode, the tall stubble in June. So for the final two years, we had four treatments. Now, Stewart Wuest’s soil temperature data proved to be very interesting. We found that temperatures, both daytime and nighttime soil temperatures, were several degrees cooler where we had the flattened stubble. We thought and we found this all the way down to 16 inches. You know, it’s quite deep. That and that surprised us as well, too. And the coolest soil temperatures were in the in the soil, a short stubble followed by the mode, then the 10 inch and then the tall stubble. You could really you could really see the temperature heat spike in the middle of clear summer day in the tall stubble where that sun was directly overhead. And keep in mind, the tall stubble, it’s all pretty much all standing vertical and there’s no residue horizontal under the ground. And this also affected seed soil moisture in the fallow as well. The short stubble tended to have the most moisture in the seed sun. So I guess, Drew, the bottom line on our findings was that every over the four years, by the end of follow, the best soil moisture in the six foot profile was pretty much a wash.

Drew Lyon: That’s interesting because, you know, back when I was in Nebraska, we were looking at stripper headers and I would say we get a different result, but then we’re a summer rainfall zone and here you get very little rain in the summer. So having that residue laying flat, I could see where that would really help more here than it would in a place like western Nebraska where you get rains in the summer.

Dr. Bill Schillinger: Yeah. So the big advantage of the tall stubble was that overwinter story–

Drew Lyon: That snow capture.

Dr. Bill Schillinger: Yeah, but then it it sort of fell down during the summer and over averaged over the four years, Drew, there were very few differences in the amount of snow, our soil water in the six-foot profile at the end of follow, although the 10-inch double was the best and the ten inch stubble is, of course, a mixture of standing and flat. And as for that mode treatment that we had the final two years.

Drew Lyon: Right

Dr. Bill Schillinger: We saw no reduction in summer water loss compared to the 10-inch stubble or the tall stubble. And we don’t really know why that happened, but we speculate that this may be because although completely covered in the ground, just like the short stubble, the residue had not been in contact with the soil, like the short stubble where it gone through a winter with rain and snow pressing it down, which was completely flattened on the ground. So anyway, those are our findings in a nutshell.

Drew Lyon: Very interesting that this couple of those things I wouldn’t have guessed going into it [ both laugh ]

Dr. Bill Schillinger: Yeah, I’m and surprised too Drew.

Drew Lyon: But that’s that’s why you do research, isn’t it?

Dr. Bill Schillinger: I guess.

Drew Lyon: So from the farmer’s standpoint, you told us what you found in your experiment. What what– from the farmer standpoint, what are the pros and cons of tall stubble?

Dr. Bill Schillinger: Yeah, well, Derek Schaffer is a very insightful farmer and he had some which he shared with us and I thought were very interesting. First, the pros. He can really cut some acres with a stripper header versus a conventional header. You know, he estimated 30 to 40% more land area per day, which would agree with the literature that we see out of the Great Plains. And so, you know, you figure with a four year average of 62 bushels an acre, that 36 foot wide stripper header on ponies combine would cut 160 acres a day versus only 115 a day with a conventional header with the same 36 foot width. And another big advantage was the much less wear on the combine’s internal separation components, because you’re not passing any straw through, you’re just passing heads and chaff. So the cons, there’s a couple. Well, the tall stubble is very difficult to seed through with deep furrowed drills without plugging. You can do it with lesser amounts of residue. But you know, our average here was 62 and we don’t have a deep furrow drill yet. That can pass through 30 inch tall, 62 bushel stubble. Maybe we’ll get there. So what Derek did to deal with this is he made two or three passes over the ground prior to seeding with what’s called a Supercoulter, which is just a big, large, coulter, fluted vertical and operated about seven miles an hour. You can fly over the ground pretty fast with that. And that would cut the the straw into small pieces. Another con, according to Derek, was the repair and maintenance costs for the stripper header. Those fingers, those rotating fingers that grab and detach, detach the wheat heads need to be replaced about every 5000 acres. In that costs about $7,000 for those fingers. Plus, it takes two people, two very long days to accomplish that task.

Drew Lyon: Oh, really? Okay.

Dr. Bill Schillinger: Yeah. Yeah. And so that and then finally, the tall stubble causes accelerated– I was surprised to hear this. The tall stubble causes accelerated wear to the underside of combines tractors, sprayers, seed drills and what have you. By rubbing through the wiring, harnesses and hydraulic lines.

Drew Lyon: That’s another one I wouldn’t have foreseen.

Dr. Bill Schillinger: The bottom line on their, Drew, was there were three well, three farmers in Adams County who had stripper headers. They don’t have them anymore. But I know a farmer in the Horse Heavens where they produce very little residue. He has one and doing fine. I also know a farmer in the intermediate region and he’s doing fine, too, but he sitting with the disk drill. You can see through lots of residue with the disk drill.

Drew Lyon: Okay, very interesting results. Some of which I would have guessed and some I wouldn’t have. So again, that’s that’s why we do this kind of research. And your ability to do it for four years and capture some of those different years was pretty key to it as well.

Dr. Bill Schillinger: And we would have kept doing it probably, Drew, but the stripper header went away. [ both laugh].

Drew Lyon: Okay, so so if people want to learn more about this study, I assume you’re publishing it in the journal. Is it going to be available any other place that people can read about this?

Dr. Bill Schillinger: Yeah, we hope to. And it will be published. It has just been accepted in the journal called Agricultural Water Management. So we’re pleased with that. And I guess if the key takeaway message from this work and I would hope to make it in an extension format with English units, you know, for farmers. But three key takeaways, I guess, is medium and tall stubble. they had the best overwinter soil water storage that significantly exceeded that of the short stubble, particularly in those two winters I referred to with the heavy snow and the snow drifting. And surprisingly, there was no advantage to mowing the tall stubble in mid-June and. And during the high evaporate evaporative demand in the summer, that tall stubble, that water really went, it’s significantly more water evaporated compared to the medium and short treatments for in and presumably because there were no horizontal residue in the tile treatment. And so finally, our study showed that that 10-inch tall stubble, which is a mixture of standing and flat, which is pretty much what the farmers are practicing now, is probably the best management practice for storing water in fallow.

Drew Lyon: I can hear a lot of farmers sighing a sigh of relief [ both laugh] that they can continue on and not have to go purchase some new equipment to try to capture more of that very valuable water, which is in short supply this year.

Dr. Bill Schillinger: Yeah, [ Drew laughs ] and every year it seems to be somewhat short supply in the dryland.

Drew Lyon: That’s true. It always is, isn’t it?

Dr. Bill Schillinger: Yeah.

Drew Lyon: Well, Bill, thank you for taking some time to share the results of this interesting study with our listeners. I appreciate you doing that for us.

Dr. Bill Schillinger: Well, thanks for having me, Drew.

[ Music ]

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 podcasting 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.


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

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