Corn Residue Removal - A CropWatch Podcast
Michael Sindelar, Nebraska Extension Educator
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12/06/2018
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Nebraska Extension Educator Michael Sindelar talks with Virginia Jim and Marty Schmer, researchers with the USDA Agricultural Research Service, about their long-term research on corn residue removal and its effects on crop production and soil quality, as well as how to manage the field after residue removal.
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- [00:00:00.153]Welcome to the CropWatch Podcast. I'm Michael Sindelar, the
- [00:00:03.044]crop assistant extension educator. For today's CropWatch
- [00:00:05.989]Podcast, we'll be talking about corn residue removal.
- [00:00:09.361]We'll be joined today by Virginia Gin and Marty Schmer.
- [00:00:12.774]Both are research scientists with the USDA ARS.
- [00:00:16.382]Yeah, my name is Marty Schmer, with USDA ARS, I'm a
- [00:00:19.577]research agronomist based out of Lincoln, Nebraska.
- [00:00:22.816]My name is Virginia Gin and I'm also with USDA ARS, and
- [00:00:27.064]I'm a research soil scientist.
- [00:00:29.952]Alright, well, I guess the first question people are
- [00:00:32.713]wondering is what do we do with corn residue after we
- [00:00:35.479]remove it.
- [00:00:38.994]Well, I think, historically, we've used it for
- [00:00:41.278]livestock feed or in some parts of the Corn Belt, we use it
- [00:00:46.767]for bedding for the dairy industry. I think in Nebraska
- [00:00:51.394]Historically, we've used it mostly as a livestock feed.
- [00:00:54.576]This has probably been going on for a number of decades,
- [00:00:57.655]probably particularly in the North Platte Valley in the
- [00:01:01.738]Panhandle.
- [00:01:03.417]They've been taking stover off for a while, and so there's
- [00:01:05.099]pockets of Nebraska where you see people take stover off,
- [00:01:08.752]particularly for livestock feed, but probably in the last
- [00:01:13.593]20 years, there was interest for cellulosic ethanol, so
- [00:01:19.801]that's where a lot of our research came from. But probably
- [00:01:22.692]most of it is going as a livestock feed.
- [00:01:26.923]Right, and we'd like to keep it on the soil
- [00:01:29.809]surface, just for purposes of soil conservation, but we
- [00:01:32.670]know just by looking out the window that you can see
- [00:01:36.178]producers are taking that material off, so a lot of our
- [00:01:40.670]research questions revolve around that.
- [00:01:44.384]Okay, so what are the effects? We'll start out with
- [00:01:47.651]probably the biggest one on maybe yield from removing
- [00:01:50.655]corn residue or corn stover?
- [00:01:54.438]I think based on the data that we've collected
- [00:01:58.160]with USDA, some of the work that's been done by University
- [00:02:01.913]of Nebraska and some other land-grant institutions is, generally
- [00:02:06.085]we don't see a yield hit, particularly in irrigated systems.
- [00:02:10.339]We sometimes see a slight yield bump. We think that's maybe
- [00:02:14.764]due, because there's less residue off, the soil gets a
- [00:02:18.185]little warmer, there's less nitrogen in mobilization, the
- [00:02:21.979]corn just grows a little faster. But there have been times
- [00:02:28.271]when we're in a drought period and under rain fad conditions
- [00:02:32.248]where we see a yield hit from taking stover off in the
- [00:02:35.199]previous year.
- [00:02:37.089]Okay, so continuing with that, what happens in the soil,
- [00:02:44.125]fertility first, when you remove residue? Has
- [00:02:47.948]there been reduction in any of the essential nutrients?
- [00:02:51.364]Well, I think what we tend to see in a lot
- [00:02:53.857]of our longer term studies is that in the surface soils,
- [00:02:56.728]we will tend to see a decrease in the organic matter
- [00:02:59.981]content, especially if you're being very aggressive with
- [00:03:03.370]the removal and doing this over a long period of time. So
- [00:03:06.661]a lot of producers may or may not choose to remove stover
- [00:03:11.098]every year, but for very aggressive removals that are
- [00:03:15.138]annual removals, then yeah, you might expect to see some
- [00:03:19.044]loss of soil organic matter in the surface. Some of the
- [00:03:24.057]nutrient export that goes along with the nutrients that
- [00:03:28.130]are in the stover itself. We have some really forgiving
- [00:03:31.416]soils though in Nebraska, so for the most part, we haven't
- [00:03:34.980]found that we needed to supplement nitrogen or any other
- [00:03:37.859]nutrient to replace what's been taken off, but again, that's
- [00:03:42.331]for a moderate rate of removal, not for super aggressive
- [00:03:47.555]rates. Then, especially if you see yield differences, you
- [00:03:52.712]would probably want to consider whether or not you need to
- [00:03:55.696]ameliorate that by adding back some nutrients.
- [00:03:59.693]Right, I think probably the biggest thing is, if you're
- [00:04:02.464]going to start, or if you have taken stover off in the
- [00:04:05.570]past is, you know, soil test your fields, get kind of a good
- [00:04:09.217]baseline, see where some of your nutrient concentrations are
- [00:04:14.025]at before you take stover off and then see if they have
- [00:04:16.598]changed dramatically. Usually you see you take some nitrogen
- [00:04:21.914]off, the second -- and then potassium is probably the highest
- [00:04:26.648]nutrient you take off. Phosphorous you take about four or
- [00:04:30.449]five pounds per ton you take off, and then sulfurs, you take
- [00:04:33.823]about three or so pounds per ton of stover removal, but we
- [00:04:39.905]haven't really seen anything in terms of needing to add
- [00:04:43.424]more nitrogen on some of our longer term sites. So I think
- [00:04:47.092]it goes back to Virginia's, you know, our soils are
- [00:04:49.891]fairly forgiving, it may take more than a decade or so
- [00:04:52.986]before you see some of those effects.
- [00:04:55.255]Well, I think it depends too on your rotation, so there's
- [00:04:58.293]a case in Iowa where they have a corn soybean rotation, and
- [00:05:02.500]the removal of corn stover actually had an impact on the
- [00:05:07.868]soybean yield because they needed more potassium, so in that
- [00:05:13.576]case, in that particular rotation, they did choose to
- [00:05:18.081]supplement with additional nutrients. But again, all of
- [00:05:21.508]those decisions on fertility depend on what your overall
- [00:05:24.669]management system is, and so doing the soil testing and
- [00:05:27.861]things like that is going to be important.
- [00:05:30.423]Alright. Now, I know that you mentioned loss of soil
- [00:05:33.729]organic matter. Does that loss of soil organic matter drive
- [00:05:36.544]any other changes in the soil that could be issues?
- [00:05:40.216]Yes, and what we find is that in systems that do stover
- [00:05:45.353]removal mechanically, the first thing that we notice is --
- [00:05:49.422]aside from potential losses in organic matter -- is there's
- [00:05:53.105]a lot of physical disturbance to the soil, because you just
- [00:05:56.737]have more machine traffic. And so, when you see things like
- [00:06:01.681]reduced soil stability, then you begin to worry a little
- [00:06:06.030]more about wind and water erosion, and any of the other
- [00:06:09.529]physical properties of the soil that go along with what
- [00:06:12.881]might be impacted by this increased machine traffic from the
- [00:06:17.850]stover removal. The organic matter content plays into soil
- [00:06:22.370]stability as well, so it's all interconnected in a lot of
- [00:06:26.630]different ways, but it's kind of intuitive to know if you've
- [00:06:31.038]got more passes because you have more intensive management
- [00:06:35.405]with mechanical removal, which could be more than two or
- [00:06:39.995]even three passes, depending on how you do it. Then yeah,
- [00:06:45.522]there are some physical soil property impacts of doing that.
- [00:06:51.632]Okay, so going on, are there other soil impacts that we
- [00:06:56.345]haven't discussed by removing corn stover?
- [00:07:01.618]There might be some biological impacts where soil health
- [00:07:07.839]is a really big and popular topic right now. And so, what the
- [00:07:13.909]idea is, is if you're changing your soil, the microbial
- [00:07:18.739]communities or your organismal communities because of
- [00:07:22.038]different management practices you're using, perhaps that
- [00:07:25.874]would affect the overall functioning of your soil. There's
- [00:07:28.974]not a lot of data yet that would really help make that link
- [00:07:34.231]between those biological properties and the functional
- [00:07:39.397]properties of the soil, but I think it's still something
- [00:07:43.658]where people want to maintain as healthy of soil as
- [00:07:46.817]Possible. And so, if there are ways to minimize the
- [00:07:50.958]impacts of the management that any producer chooses to use,
- [00:07:55.534]then biology may be one of those. But whether or not
- [00:08:00.121]that's going to be a major part of any decision,
- [00:08:04.058]particularly an economic decision, that's going to depend
- [00:08:07.531]on producer to producer.
- [00:08:09.815]And I think if a producer's long-term goal is improving
- [00:08:14.015]soil health, then taking residue off would --it just takes
- [00:08:22.038]a little longer for that -- for any of your goals to happen.
- [00:08:26.521]So generally it's not -- best management practices with
- [00:08:30.653]stover removal or any residue removal. Generally you can
- [00:08:34.717]maintain the soil -- some of the soil conditions, but if
- [00:08:37.452]you want to improve it, then generally you want to keep
- [00:08:40.659]as much of that residue, if not all of that residue on the
- [00:08:43.174]ground.
- [00:08:45.120]Okay, now you mentioned earlier different number of passes
- [00:08:50.801]with different equipment, what would be a recommended setup
- [00:08:55.008]and what equipment would people need if they were interested
- [00:08:58.225]in bailing residue?
- [00:09:00.685]Well one of the first ideas was that we would just maybe
- [00:09:05.542]send it through the combine, so that either you could have
- [00:09:09.475]it spread out -- you know, just have it dumped right under
- [00:09:12.720]instead of spreading it, you just have it dumping in
- [00:09:15.123]there. There's new equipment with the corn header that it
- [00:09:17.358]actually will make a windrow underneath the combine, so
- [00:09:20.309]it's not sending it through the combine. It's just
- [00:09:22.644]collecting it, cutting it, and then you can select how much
- [00:09:25.979]area or how much biomass you want to take from the windrow
- [00:09:31.735]off the corn header. A lot of times, farmers, I think have
- [00:09:36.704]more of an interest in having decoupled from the harvesting.
- [00:09:41.165]So what they want to do is, usually, they want to harvest
- [00:09:44.081]the corn first, and then go back in and harvest the residue,
- [00:09:48.015]and so what that usually involves is maybe something as
- [00:09:51.186]a rake, a hay rake that can make a windrow. A lot of times
- [00:09:56.446]people will also use the self-propelled disc mower, and
- [00:10:00.382]a lot of people use kind of a corn shredder, and then
- [00:10:04.059]usually that has an accumulator at the end where they can
- [00:10:07.899]mix it into a windrow, and then, either using a large
- [00:10:10.997]square baler or a round baler to collect the stover.
- [00:10:14.702]I think the thing that we've noticed is that how you harvest
- [00:10:18.154]it also depends on how much stover is retained, or how much
- [00:10:21.163]biomass is retained, because some of this equipment
- [00:10:24.238]available, if you're too aggressive, it really chops up. It
- [00:10:28.114]makes the stover into small particles, and so even though
- [00:10:33.799]you can't collect everything, or you think you're collecting
- [00:10:37.333]a certain amount, or you're leaving a certain amount, a
- [00:10:40.356]portion of that will actually leave the field through
- [00:10:42.883]wind, particularly in central Nebraska, or it'll degrade
- [00:10:47.197]quicker and oxidize into the atmosphere quicker. So you
- [00:10:50.342]may not be getting all that full effect of maintaining the
- [00:10:55.021]cover that you want, so sometimes we say, generally
- [00:11:00.101]for stover, it's about 50% of your grain, so total biomass
- [00:11:04.449]of corn, of the harvest index, is about, we generally
- [00:11:08.091]approximate as 0.5, so you have half of it as grain, half
- [00:11:11.675]of it as biomass, so even if you take half of that biomass
- [00:11:15.090]off, depending on how you used the equipment, what equipment
- [00:11:19.398]you used, some of it may not be retained as much as you
- [00:11:23.712]would initially have thought, so that's one thing to
- [00:11:28.720]consider, what type of equipment you want to use. I don't
- [00:11:31.549]think there's one piece of equipment available right now
- [00:11:34.926]that's the dominant, I think most people either rake it or
- [00:11:38.351]use some type of shredder for that.
- [00:11:42.311]What would be the best economic decision for equipment
- [00:11:45.978]just to use?
- [00:11:47.973]Well, I think any management practices that reduce the
- [00:11:52.211]number of machine passes that you have on your field
- [00:11:54.871]is one that's going to have a big impact on your pocketbook,
- [00:11:58.403]simply because you're using a lot less fuel, and fuel
- [00:12:01.774]happens to be the category that takes up a lot of expense.
- [00:12:05.889]So if you have, say an option where you can mow and windrow
- [00:12:10.712]at the same time, or mow and swath at the same time, instead
- [00:12:13.873]of having to mow and then rake as a separate pass, that's
- [00:12:17.516]probably some place where you could have some savings.
- [00:12:21.839]Yeah, and I think it's just basically, you also have to
- [00:12:26.614]evaluate your labor, how much labor you have at a certain
- [00:12:30.113]time is another consideration to take into account.
- [00:12:34.039]Alright, so we kind of touched on it, what would be the
- [00:12:37.280]recommended practices for removing residue responsibly?
- [00:12:43.040]I think the bottom line that Virginia alluded to was the
- [00:12:46.659]potential loss in soil organic matter at the surface, so
- [00:12:50.716]what we recommend is if you're taking residue off, whether
- [00:12:54.382]it's just one time or a few times in a rotation,
- [00:12:59.850]you know, 50% of the time that you have corn or something
- [00:13:04.847]like that, that you have to reduce your tillage. So tillage
- [00:13:10.003]and removing stover or most crop residues is really not
- [00:13:14.444]compatible, so if you're going to take residue off or corn
- [00:13:18.488]stover off, you need to go, at the minimum, probably kind of
- [00:13:22.787]a split tillage, or a strip tillage type system, or what
- [00:13:26.399]we would probably recommend is no tillage. Convert over
- [00:13:30.221]to no-till, because what we've found from our long-term
- [00:13:34.399]research is that by going no-till, you tend to get a small
- [00:13:38.568]yield bump from taking the residue off, and so you tend to
- [00:13:43.381]get similar yields than if you have a disc tillage system.
- [00:13:47.076]So you tend -- the yields are exactly the same, but you
- [00:13:49.941]reduce the amount of potential soil impacts that you would
- [00:13:54.972]by having tillage coupled with residue removal.
- [00:14:00.314]Okay, and so we've heard some negative impacts to the
- [00:14:03.135]soil that can happen when we remove residue, what are some
- [00:14:06.900]options to remediate the soil itself?
- [00:14:11.260]Well cover crops are very popular right now, and it's not
- [00:14:16.473]just the popularity part of it, there's some real functional
- [00:14:19.474]aspects to having a cover crop and keeping soil cover.
- [00:14:23.385]When you're removing residue, even though with the improving
- [00:14:28.000]amounts of biomass and yield we get, that means we have a
- [00:14:30.612]lot more residue on the soil surface. Using a cover crop to
- [00:14:35.811]replace some of the biomass that you're taking off as stover
- [00:14:40.869]is a good idea for helping to restore some of the organic
- [00:14:44.853]matter in that system, as well as some stability to the
- [00:14:47.654]physical soil property because the roots of the plants are
- [00:14:50.716]there. So that's one option, and another option is in
- [00:14:55.871]bringing back, again the organic matter that you're losing
- [00:15:00.062]with stover removal, is to use things like animal manure
- [00:15:04.663]or other kinds of green manures and incorporating that into
- [00:15:08.903]your system. We have both of those types of treatments in a
- [00:15:13.395]Long-term experiment that's at the South Central Ag
- [00:15:17.323]Laboratory here in Clay Center. And it's been using those
- [00:15:21.584]two practices to compare against where we've removed the
- [00:15:25.398]stover, has shown to have some benefit for our crop yields
- [00:15:29.205]and some of our soil properties. Now it takes a long time
- [00:15:34.876]for the management benefits to show up, just because
- [00:15:39.975]the soils are, again, very fertile here and they're very
- [00:15:42.687]forgiving, but I think it's that long-term perspective in
- [00:15:46.026]maintaining the soil health and sustainability where if that
- [00:15:51.091]could be one of the things that helps people make decisions
- [00:15:55.596]on management, then that's where we would push folks to
- [00:15:59.913]consider it.
- [00:16:02.290]And I think some general guidelines I would recommend for
- [00:16:05.972]producers is that probably for fields that are above 180
- [00:16:10.771]bushel is probably the minimum threshold for taking stover
- [00:16:15.896]removal, so anything below 180 bushel, you need to probably
- [00:16:21.475]leave the stover on. Fields that are averaging over 180
- [00:16:26.464]bushel, you could probably consider taking stover off, and
- [00:16:31.676]probably, right now our recommendation is take no more than
- [00:16:36.000]two tons per acre of stover off, that generally means that
- [00:16:41.297]the minimum amount of stover that's retained will ensure
- [00:16:47.835]that we meet the guidelines for minimizing soil erosion
- [00:16:49.957]from wind or water, and also maintaining our soil organic
- [00:16:54.294]matter concentrations in our soils. Another thing to consider
- [00:16:58.170]is if you have sloping soils, I highly recommend not
- [00:17:02.748]harvesting stover off of slopes and fields that are greater
- [00:17:08.838]than 4% or 5%, and if you're in a corn soybean rotation,
- [00:17:13.887]we'd recommend that you don't take the stover off every
- [00:17:17.891]year, probably do it once every four years. In a continuous
- [00:17:21.884]corn system, we'd probably recommend you don't take stover off
- [00:17:25.893]every year, maybe at minimum probably no more than once
- [00:17:31.740]every two years or so 50% of the time.
- [00:17:35.397]Alright, so do either of you have any online web resources
- [00:17:40.287]that you would recommend for anybody interested in removing
- [00:17:43.174]residue?
- [00:17:45.739]Well, clearly the NebGuides that are provided by UNL
- [00:17:49.398]Extension are an easy resource to use and refer to. There
- [00:17:53.762]are some resources available through extension in Iowa where
- [00:17:57.652]they do some residue removal as well, but probably not as
- [00:18:02.184]much as what we do in this state.
- [00:18:06.393]And the CropWatch guidelines online are excellent
- [00:18:10.240]Resources. They're updated continuously by the University of
- [00:18:14.201]Nebraska. They're a great resource for producers.
- [00:18:20.538]Thank you for your time, Virginia and Marty.
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