9 - 2020 Soybean Management Field Days - Interseeding Cover Crops in Soybean: Key Considerations for Success
Interseeding Cover Crops in Soybean: Key Considerations for Success - Chris Proctor, Nebraska Weed Management Extension Educator. Learn about: Overcoming challenges to cover cropping in a corn/soybean system; Interseeding Options; and Key Considerations for Interseeding Success (Timing of Planting and Cover Crop Selection)
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[00:00:06.850]I'm Chris Proctor.
[00:00:08.050]I'm a weed management extension educator
[00:00:10.040]at the University of Nebraska.
[00:00:12.120]I'm just gonna highlight
[00:00:14.640]some of the work we've done
[00:00:15.660]for the Soybean Management Field Days this year
[00:00:18.030]at our different locations
[00:00:19.810]trying to test interseeding of cover crops
[00:00:23.650]with the drill interseeder
[00:00:25.462]into soybean and in some of what we learned.
[00:00:29.570]But I wanna highlight this idea,
[00:00:31.220]this concept of interseeding in general first,
[00:00:34.660]and then I'll talk a little bit
[00:00:35.543]about the study as I get towards the end here.
[00:00:41.290]And so if I just think about cover crops
[00:00:42.593]and in general in corn and soybean
[00:00:45.320]which are predominantly how we're testing
[00:00:49.480]the use of cover crops in our state
[00:00:51.740]and how we're using them,
[00:00:53.920]there's just a number of challenges to cover cropping system
[00:00:57.670]within corn and soybeans.
[00:00:58.830]So you have that short window
[00:01:01.010]for establishment after harvest.
[00:01:03.430]There's always the question,
[00:01:05.070]do the benefits that I gained from my cover crops,
[00:01:07.110]do they justify the expense or the cost?
[00:01:10.000]And what about, how is it gonna,
[00:01:12.610]not only the direct cost,
[00:01:14.390]but how might that influence crop yields?
[00:01:19.220]There's a few things that we've known about
[00:01:20.600]this idea of how do we successfully establish cover crops
[00:01:25.290]within our corn and soybean systems?
[00:01:27.430]And so I just gonna highlight just a couple of those ideas.
[00:01:29.420]One being planting date has a pretty strong influence
[00:01:32.260]on how much cover crop biomass we accumulate.
[00:01:34.500]And we know that the more biomass that we accumulate
[00:01:38.100]that tends to be pretty strongly correlate
[00:01:40.650]or relate to the benefits that we see in those systems.
[00:01:44.250]And so this is just showing a study over two different years
[00:01:48.324]in Central Nebraska,
[00:01:49.800]and you can see the earlier the planting date
[00:01:52.330]on that bottom axis,
[00:01:53.590]the more cover crop biomass that we accumulated
[00:01:57.170]which are those green bars,
[00:01:59.020]that Spring biomass.
[00:02:00.170]And so planting in September, early October,
[00:02:04.190]that generated a lot more biomass
[00:02:05.760]than waiting until the very end of October to plant.
[00:02:09.300]We've seen this visually as well.
[00:02:12.530]And so you can just see this progression of planting dates
[00:02:17.960]from early September until the later part of October
[00:02:21.810]and there's a pretty significant difference
[00:02:24.040]come the next Spring.
[00:02:25.420]So this is the end of April when these pictures were taken.
[00:02:29.610]We had quite a bit more cover crop biomass showing.
[00:02:33.510]The other side of the coin in terms of biomass accumulation,
[00:02:37.080]if you can delay termination,
[00:02:39.450]that's a pretty big difference in biomass accumulation.
[00:02:41.960]So this was showing some data
[00:02:43.600]from a previous Soybean Management Field Day study,
[00:02:47.340]looking at termination date.
[00:02:48.640]And so this was a difference of about two weeks
[00:02:50.770]in termination timing.
[00:02:51.630]So we went from mid May
[00:02:55.366]to early June termination timing.
[00:03:00.107]You can see the two weeks difference
[00:03:02.310]made a pretty sizable difference in the amount of biomass
[00:03:05.970]that we were able to accumulate at that time of the year.
[00:03:07.950]And so that's another opportunity within the system
[00:03:11.200]to accumulate biomass.
[00:03:12.290]These are some of the ways that we've looked at,
[00:03:14.110]that we've studied more thoroughly.
[00:03:19.823]The question is what other opportunities are there in terms
[00:03:22.290]of getting cover crops into our systems
[00:03:24.760]into corn and soybean systems?
[00:03:26.930]And so there's other ideas
[00:03:28.214]that have been explored.
[00:03:29.900]So this idea of can we add wheat to the rotation
[00:03:32.110]at a third crop rotation?
[00:03:33.882]That just would give you a little bit broader window
[00:03:36.470]for establishing a cover crop.
[00:03:38.500]Seed corn, silage, using a shorter season maturity groups.
[00:03:43.120]All of these are just ways that you can gain a little bit
[00:03:46.560]of an extended season for establishing
[00:03:48.580]and growing a cover crop in Nebraska.
[00:03:51.610]Green planting is another one.
[00:03:53.470]So that would be delaying termination
[00:03:55.860]or delaying how long you let that cover crop
[00:03:57.610]grow in the Spring.
[00:03:59.310]There's certainly others that could be talked about.
[00:04:02.060]And then the last one I'll highlight
[00:04:03.780]and the one I'm interested to cover today
[00:04:05.530]is this idea of interseeding.
[00:04:08.740]When we think of interseeding,
[00:04:09.859]there's really two ways that it's done.
[00:04:11.720]So there's broadcast interseeding.
[00:04:13.210]So this would be an airplane or high-clearance applicator.
[00:04:16.010]And typically this is a late season application.
[00:04:18.280]And so you think of towards the end of the year,
[00:04:21.240]R5-R6 in corn,
[00:04:23.540]just as soybean leaves start to yellow
[00:04:25.730]before the leaves start to drop,
[00:04:27.000]often cover crops could be interseeded at that time.
[00:04:31.400]Really the drawbacks to interseeding this way
[00:04:33.861]is when you broadcast the seed just falls
[00:04:37.720]on top of the soil surface.
[00:04:39.030]A lot of it can get hung up in the plant canopies.
[00:04:42.170]So you just have poor seed to soil contact.
[00:04:45.090]And the other challenge
[00:04:45.980]is you need really timely precipitation.
[00:04:49.370]So if you're in a dry land environment and it doesn't rain
[00:04:51.910]within a couple of days of interseeding,
[00:04:56.010]your establishment tends to go way down
[00:04:58.350]or else you're gonna need to think about
[00:05:00.470]maybe a late season irrigation
[00:05:02.110]where you typically wouldn't irrigate,
[00:05:03.810]but if you have that seed on top of the soil,
[00:05:06.010]irrigation might be warranted.
[00:05:10.140]And then another type of interseeding
[00:05:12.250]that's starting to gain more attention
[00:05:14.470]is drill interseeding.
[00:05:15.860]And so there's a number of companies,
[00:05:18.220]a number of farmers that have just innovated these rigs
[00:05:23.220]or where they're kind of their high-clearance machines,
[00:05:25.470]where they can be driven through the field
[00:05:28.600]earlier in the season.
[00:05:29.720]This is kind of the V3 to V5 window in corn.
[00:05:34.583]When a tractor can still get through the field
[00:05:36.730]and the toolbars high enough to clear
[00:05:39.400]those plants without damaging them.
[00:05:41.380]But the advantage is you can use
[00:05:44.280]drill openers to put the seed into the soil
[00:05:47.000]and so you have a lot better seed to soil contact.
[00:05:50.630]And most of the work to date has been in corn
[00:05:53.330]evaluating how effective this type of system is.
[00:05:57.570]So I just thought I'd highlight maybe some ideas or things
[00:06:01.300]to think about to be successful with this type of system.
[00:06:05.690]So the timing of planting is certainly critical.
[00:06:13.118]When the seed goes into the system
[00:06:15.700]is gonna strongly influence how effective it can be,
[00:06:18.950]and just as a way to highlight that
[00:06:21.460]there was a study done a handful of years ago
[00:06:24.450]at our South Central research center,
[00:06:28.410]looking at the timing of interseeding in corn.
[00:06:32.040]I just show a couple of pictures here to show.
[00:06:34.990]In this system,
[00:06:36.207]when we seeded the cover crop at the same time as the corn,
[00:06:39.160]it had a pretty detrimental influence on that corn.
[00:06:42.180]And so that early timing just wasn't effective in corn.
[00:06:45.890]So getting the timing right is really critical.
[00:06:51.400]Cover crop selection.
[00:06:52.700]Now that you're planting cover crops in an environment
[00:06:55.600]where they're in some kind of competition
[00:06:58.089]with our cash crop,
[00:07:00.820]picking the right cover crop is really critical.
[00:07:04.530]What kind of light is available to that cover crop?
[00:07:07.250]How does that environment favor certain crops over another?
[00:07:10.570]Again, this is where there isn't a lot of research being,
[00:07:15.780]research is fairly new.
[00:07:17.240]Let's put it that way.
[00:07:18.130]There isn't a lot of information yet
[00:07:19.650]on what are the most effective crops
[00:07:21.850]for these drill interseeding environments.
[00:07:24.830]In the corn environments,
[00:07:27.370]the cover crops that I've listed here
[00:07:29.980]are ones that have been recommended.
[00:07:34.620]And so you can see annual rye.
[00:07:36.050]Some of the clovers tend to do okay in that environment.
[00:07:40.310]A lot of these environments, as you go farther north,
[00:07:44.570]the cropping systems tend to change the environments
[00:07:47.530]under those canopies is a little bit different,
[00:07:49.410]and so there's even suggestion of cereal rye, oats.
[00:07:54.640]These might even work in the Northern parts of Nebraska.
[00:07:58.990]But it's certainly something to consider
[00:08:02.100]is what cover crop are you wanting to put
[00:08:04.210]under these canopies and how well are they gonna survive
[00:08:06.388]under that environment?
[00:08:09.200]And then the last one I'll highlight here
[00:08:12.620]is herbicide selection.
[00:08:14.030]Now we've kinda changed our cropping system.
[00:08:16.500]So we've gone from really managing weeds
[00:08:19.360]with just the presence of corn or soybeans,
[00:08:21.510]but now we've added another crop into that system.
[00:08:24.550]And so our herbicide programs most likely
[00:08:27.210]need to be adjusted or adapted to consider that
[00:08:30.830]because many of the cover crops that we might use
[00:08:33.810]in these systems
[00:08:34.889]would not work well with a lot of our herbicides
[00:08:39.070]or herbicide programs.
[00:08:42.050]Now we're kinda led to think about
[00:08:44.631]what are the factors that influence
[00:08:46.680]or affect herbicide persistence?
[00:08:49.770]'Cause the longer that herbicide persist
[00:08:51.670]in that environment is gonna influence
[00:08:55.710]how that herbicide might impact our cover crop.
[00:08:59.240]So rainfall, soil texture, organic matter, pH,
[00:09:03.050]the rate of the herbicide,
[00:09:05.470]just the chemistry that herbicide itself, how long does it,
[00:09:08.130]what's the half-life of this herbicide.
[00:09:11.370]Those can all influence how well
[00:09:14.470]it might match with it with a cover crop.
[00:09:17.460]Just for an example, here's an herbicide label, Optill PRO.
[00:09:23.200]And if you look in this table here,
[00:09:25.850]this is showing the label recommendations
[00:09:28.810]on how long you need to wait
[00:09:30.150]between applying the herbicide
[00:09:31.750]and planting the subsequent crop.
[00:09:34.340]And they have a category for other crops.
[00:09:36.970]And most of our cover crops would fall under that category
[00:09:39.830]in that they haven't been researched thoroughly.
[00:09:44.210]For this herbicide that's a 40 month restriction.
[00:09:46.740]And so you can imagine if you applied Optill PRO
[00:09:49.520]and you wanted to plant a clover into that system.
[00:09:52.370]Well, according to the label,
[00:09:53.320]they would recommend you wait 40 months
[00:09:54.980]before applying that,
[00:09:56.650]planting that cover crop.
[00:09:57.660]So that's not feasible for any of our systems.
[00:10:00.370]And so thinking about the herbicides
[00:10:02.110]that you select is important.
[00:10:03.930]I'd highlight another label just to say more and more labels
[00:10:07.470]are now containing language that talk about cover crops.
[00:10:10.410]Here's a label in DiFlexx DUO that actually has a section
[00:10:14.600]that talks about cover cropping
[00:10:16.083]and their recommendation is if you're using a cover crop
[00:10:19.960]to either do a bioassay,
[00:10:22.190]how well that cover crop might grow on the soil,
[00:10:24.790]or to at least acknowledge that you're doing it
[00:10:26.770]at your own risk.
[00:10:29.046]If you wanna push the envelope
[00:10:31.980]and plant a little bit sooner your cover crop,
[00:10:34.750]you can try that
[00:10:35.910]and it may very well work in these systems,
[00:10:37.880]but this is something that the companies
[00:10:39.811]haven't thoroughly tested
[00:10:41.200]and so you need to kinda test it yourself.
[00:10:45.200]And so that's what the labels would describe.
[00:10:47.510]And then I just highlight,
[00:10:48.850]there's other resources available
[00:10:50.370]that would give you some indication of how,
[00:10:52.960]what herbicides might be compatible
[00:10:55.390]with different cover crops.
[00:10:58.320]We have our guide for weed disease and insect management,
[00:11:00.860]and we have a lot of these tables talking about herbicide,
[00:11:04.140]carry over replant restrictions and so forth
[00:11:07.360]that could be used to think through this question.
[00:11:10.970]There's some resources that talk about
[00:11:12.350]how to conduct a field bioassay.
[00:11:14.637]And so if you wanted to test yourself,
[00:11:18.090]how might a cover crop grow given your soil conditions
[00:11:21.870]and how much your herbicide
[00:11:23.080]you might have left in your soil.
[00:11:24.380]This would be one way to test it.
[00:11:26.930]Then another one I'd highlight,
[00:11:27.940]and this is one that is probably one
[00:11:29.870]of the more developed resources right now.
[00:11:31.640]PennState has done a nice job of listing a number of tables
[00:11:34.980]and how different herbicides might be compatible
[00:11:40.770]with different cover crops.
[00:11:43.320]And so I just highlight
[00:11:45.320]that webpage here.
[00:11:47.690]You can easily Google this and track it down.
[00:11:51.660]And I pull out one of the tables that they list there
[00:11:55.370]on their website.
[00:11:56.280]This is showing a number of soybean residual herbicides
[00:12:00.190]and how they might influence either a grass,
[00:12:02.800]a legume or a brassica cover crop.
[00:12:04.570]And so it kinda gives you at least
[00:12:06.120]some kinda reference as you're thinking through
[00:12:08.490]what herbicides might work best with cover crops.
[00:12:14.120]And then finally thinking about other considerations
[00:12:18.590]for effectively interseeding cover crops
[00:12:21.520]into soybeans in particular.
[00:12:23.650]And these are questions that I don't think
[00:12:25.280]we have good answers to,
[00:12:26.210]but I think we're gonna have to think through
[00:12:28.290]and soybean population.
[00:12:30.890]So a lot of cover crop success in interseeding
[00:12:33.750]is there enough light and resources for that cover crop
[00:12:36.360]to at least survive until that crop is harvested.
[00:12:39.860]So is lowering the soybean population down,
[00:12:43.330]is that an effective way
[00:12:45.670]to allow more light into the system?
[00:12:49.210]Row direction is something that's been considered.
[00:12:52.300]Is a North-South row more effective
[00:12:55.010]at letting light into the canopy
[00:12:56.290]compared to an East-West row.
[00:12:58.710]The stature of soybean plants.
[00:13:01.130]A lot of what we select our plants on,
[00:13:03.730]we might have to start thinking of different parameters
[00:13:05.730]that we use for cultivating hybrid selection.
[00:13:09.110]Are short stature plants better?
[00:13:12.930]It's thinking about maybe some of the determinant varieties
[00:13:15.270]that would cease growth at a certain height,
[00:13:17.580]maybe allow a little more light into that system.
[00:13:20.340]So again, there's a number of questions
[00:13:21.590]that we could begin to ask
[00:13:22.980]relative to making this successful in soybean.
[00:13:26.958]Those are some of the ideas we had in mind
[00:13:28.930]as we design our study for this year's field days.
[00:13:34.510]And so we have our four locations
[00:13:37.550]across our state.
[00:13:39.110]Arlington, Shelby, Elgin and Hildreth.
[00:13:44.720]And so we had,
[00:13:45.610]it was about the second week of May give or take
[00:13:48.670]that we planted most of our soybean.
[00:13:50.750]And then we came back.
[00:13:52.250]It was about a month,
[00:13:55.290]maybe a little bit more than a month later
[00:13:56.720]that we came back and we interseeded
[00:13:58.180]with a drill interseeder at those locations.
[00:14:02.660]And the soybean was roughly V3 growth stage
[00:14:05.540]when we interseeded.
[00:14:07.380]We had two soybean cultivars that we evaluated.
[00:14:11.756]One was kind of a typical maturity group 3 cultivar
[00:14:17.170]of this growing in Nebraska
[00:14:18.003]and then we tried to select another one
[00:14:19.920]that had a little bit shorter stature
[00:14:22.390]hoping that we might see a little bit more light
[00:14:24.540]into the canopy with that cultivar.
[00:14:27.530]We seeded all of our study
[00:14:30.540]at 100,000 soybean seeds per acre.
[00:14:34.839]And then we had two different herbicide programs
[00:14:36.940]that we evaluated.
[00:14:37.850]And so we looked at what we would call a typical program,
[00:14:41.850]or we had a burndown plus a pre-emerge herbicide.
[00:14:45.520]In this case, we used valor
[00:14:47.800]followed by a post-emerge herbicide,
[00:14:51.110]which we only use roundup for this particular study
[00:14:54.030]compared to no pre-merger beside it all.
[00:14:55.867]And so we were wanting to know,
[00:14:57.900]was our herbicide program having any influence
[00:15:00.030]on the establishment of our cover crop
[00:15:02.090]in this interseeded environment.
[00:15:04.750]And then for the cover crop that we utilized,
[00:15:06.720]again we don't have a good frame of reference,
[00:15:08.500]so what we came up with for this particular study
[00:15:11.330]was to evaluate.
[00:15:13.550]We planted a mixture of annual ryegrass
[00:15:15.930]at 2 pounds an acre mixed with a winter wheat
[00:15:18.760]planted at 10 pounds an acre.
[00:15:20.010]And so that was interseeded into the cover crop.
[00:15:24.970]Or excuse me, that cover crop was interseeded
[00:15:26.670]into our soybean.
[00:15:28.390]And so those have been evaluated throughout this season
[00:15:32.540]and as that data becomes available,
[00:15:35.700]that's gonna be compiled and made available to you
[00:15:40.280]in our research booklet here
[00:15:42.060]at the end of the season with the yields
[00:15:44.070]and the cover crop biomass and all that.
[00:15:48.572]The question is what are the common species and mixes used
[00:15:53.260]in these interseeding environments for cover crops?
[00:15:57.350]One, there's just not a lot that does well
[00:15:59.820]under that canopy.
[00:16:01.610]So the most common in corn is annual ryegrass.
[00:16:06.950]I think that one tends to do a little bit better
[00:16:08.610]under low light environment,
[00:16:09.580]and then there's a couple of clovers that seem to do okay
[00:16:12.840]and so I think some of the crimson clover
[00:16:16.030]is one that gets talked about frequently.
[00:16:19.550]I know there's more and more research coming out.
[00:16:22.260]I know some of our colleagues are doing some research
[00:16:25.520]in the central part of the state,
[00:16:26.353]and they're looking at much broader mixes.
[00:16:28.940]I think trying to capture some nitrogen fixing species
[00:16:32.800]along with some grass species and even some brassicas
[00:16:35.260]and seeing if they can make those successful
[00:16:38.780]at least in a corn environment.
[00:16:40.460]And in corn, you have just a little bit more light.
[00:16:42.160]I think the challenge is just that much more in soybean.
[00:16:44.900]And so I think we're gonna have to adapt our soybean system
[00:16:48.500]more dramatically if we wanna make this work in soybean.
[00:16:52.410]Does that answer your question?
[00:16:54.170]I don't have good answer but that's kinda what I know.
[00:16:58.270]The comment in question is we've used one suggestion
[00:17:02.460]to accumulate more biomass following soybean.
[00:17:05.160]The soybean crop is to shorten the maturity group
[00:17:08.180]that's used in that system
[00:17:09.530]so that harvest would occur a little bit sooner.
[00:17:12.010]And so in the research that we've done on that,
[00:17:14.700]what we've seen
[00:17:16.670]is that most,
[00:17:19.140]we really don't see any yield penalty
[00:17:21.340]all the way down to about a maturity group 3,
[00:17:23.670]maybe a very late two,
[00:17:26.130]but then from a three down to a two for Nebraska,
[00:17:31.850]for most of the Nebraska locations we've tested,
[00:17:33.940]we see about a three or four bushel decrease in yield
[00:17:37.700]to go from a three down to two,
[00:17:39.780]but we gained about two weeks of growing season
[00:17:42.170]in terms of harvest date.
[00:17:44.410]And so there's a window in there.
[00:17:46.190]I think in the kind of the mid to late 2s,
[00:17:50.470]your yield penalty would be fairly minimal,
[00:17:53.000]but you would probably gain in somewhere
[00:17:55.470]between a week to 10 days in terms of timing
[00:17:58.410]to establish a cover crop in the fall.
[00:18:01.200]So that's kind of our been our recommendation for Nebraska,
[00:18:04.030]for most of the parts of Nebraska.
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