2 - 2020 South Central Ag Lab Field Day
South Central Ag Lab Field Day
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- [00:00:04.890]I'm Sabrina Ruis.
- [00:00:05.780]I'm a research assistant professor with
the agronomy and horticulture department
- [00:00:08.930]at the University of Nebraska-Lincoln.
- [00:00:11.350]and I'm going to talk today
a little bit about,
- [00:00:13.760]some corn residue removal study,
that we have going out on out here.
- [00:00:19.430]And the study has been going
on for about six years.
- [00:00:23.330]So I'm going to present both
three-year and six year data.
- [00:00:26.780]And this topic is actually
really important because we
- [00:00:31.460]kind of know the generally high rates
of, crop residue removal,
- [00:00:36.140]can have negative impacts on soils. And,
- [00:00:40.190]but we really don't have
a lot of long-term data,
- [00:00:43.580]particularly from the Great Plains region.
- [00:00:46.040]So what we did was we assessed the impacts
of crop residue removal that are moveable after
- [00:00:50.030]three and six years on soil
properties and crop yields.
- [00:00:55.010]So our experiment is
located here at clay center.
- [00:00:59.690]We also have a sister site, just
in, in the East that is rain fed gear,
- [00:01:04.340]it's irrigated, but I'm going to
focus on the irrigated site itself.
- [00:01:09.500]And so we have treatments of zero 25,
- [00:01:12.920]50 75 and 100% residue removal.
- [00:01:17.120]and you'll see on the slide that it does
talk about cover crops a little bit.
- [00:01:20.090]That is also part of the project.
- [00:01:21.620]What I'm going to focus on
the residue removal apart.
- [00:01:25.370]I will be talking a little bit
later about the cover crop portion.
- [00:01:29.960]And so we measured for this study,
- [00:01:32.360]corn grain yield and a variety
of soil health parameters,
- [00:01:37.730]that will include lay bile or easy to
degrade organic matter total organic
- [00:01:41.810]matter water erosion, potential
or soil structural quality,
- [00:01:45.950]compaction, water, infiltration, water
retention, and, heat transfer.
- [00:01:51.710]So first we're going to talk
about particulate organic matter.
- [00:01:55.250]And in year three we saw no
effect of crop residue removal.
- [00:02:01.040]And in year six,
- [00:02:03.110]we found that anything
over 25% removal basically
- [00:02:07.520]reduced that particular organic
matter or lay organic matter.
- [00:02:11.180]Now particulate organic matter is
really important because that's what the
- [00:02:14.450]microbes are going to be feeding on.
- [00:02:16.400]As they feed on that particulate
organic matter, they are,
- [00:02:21.260]are acting on that. They are,
- [00:02:24.350]decomposing that and they produce various
glues and sticky substances that help
- [00:02:28.430]to form aggregates.
- [00:02:30.560]So when we reduced our particulate
organic matter, we're reducing our,
- [00:02:35.330]food for the microbes and
thereby probably our aggregation,
- [00:02:38.420]which I will get to momentarily,
- [00:02:40.970]for total organic matter or overall
organic matter at this site,
- [00:02:44.750]we saw no effect after three years,
- [00:02:48.770]from residue removal,
- [00:02:49.790]but similar to the particular
organic matter or lay bile,
- [00:02:54.110]the total organic matter did also
decrease with crop has removal starting at
- [00:02:59.020]about 25% and higher.
- [00:03:03.010]What aggregate stability is, just are,
- [00:03:06.160]you can think of that as
our water erosion potential
- [00:03:11.110]and on the slide I'm showing both
the rain fed in the irrigated site.
- [00:03:14.410]I'm going to,
- [00:03:15.130]I'm just talking about the irrigated
sections site that are circled.
- [00:03:19.330]And in year three we saw
no effect of croppers
- [00:03:23.680]removal on what aggregate
stability or aggregate size.
- [00:03:27.730]And you can see on the Y axis of the
slide that it says, mean weight, diameter,
- [00:03:32.340]water, stable aggregates, just
think of it as aggregate size.
- [00:03:36.580]in year six,
- [00:03:38.110]we saw that any residue
removal rate greater than,
- [00:03:41.620]or equal to 50% reduced
our aggregate size.
- [00:03:45.880]So treatments with 50 75 or
a hundred percent removal,
- [00:03:50.170]they are more susceptible
to lottery erosion.
- [00:03:53.080]And so let's say we
get a heavy rain storm.
- [00:03:56.170]They're more likely to
see runoff compared to our
- [00:04:01.000]zero and 25% because the
aggregates are smaller.
- [00:04:04.330]They're more easily carried
by water compaction and water
- [00:04:09.010]infiltration are the next two properties
that we're going to talk about.
- [00:04:12.490]And we didn't measure either
of these in year three,
- [00:04:15.130]just because they're a little bit
slower to change with management.
- [00:04:18.790]after six years we saw no effect
of crop residue removal rate on saw
- [00:04:23.620]compaction parameters. And we, we,
- [00:04:26.080]we looked at soil compaction from
two different angles, woke density,
- [00:04:29.320]which is our massive,
- [00:04:31.270]soil over a set volume and
then penetration resistance,
- [00:04:35.470]which is the,
- [00:04:37.360]you can kind of think of it as the
soil is resistance to something moving
- [00:04:40.660]through it, like a root moving
through the soil or an earthworm that's,
- [00:04:45.820]it's going to be what they are
seeing as they move through the soil.
- [00:04:48.910]And with our, our site here,
- [00:04:51.670]we saw no effect of compaction
or no effect of residue removal
- [00:04:56.620]on compaction, water infiltration.
- [00:04:59.110]We looked at initial water
infiltration and we saw again,
- [00:05:01.900]no effect of crop residue removal on,
- [00:05:06.220]water infiltration,
water retention. We,
- [00:05:09.520]we measure a number of parameters.
When we look at water retention,
- [00:05:13.510]we have what's called field capacity,
- [00:05:15.790]permanent wilting point or PWP
and plant available water or paw
- [00:05:21.730]field capacity is so let's
say you have a saturated soil,
- [00:05:25.810]and then you let that drain and
a silt loam or silty clay loam
- [00:05:30.760]for 24 hour 48 hours ish,
- [00:05:34.720]depending on the soil.
- [00:05:36.790]And then all everything that's gravity
drained out of that what's left is our
- [00:05:41.710]water content at field capacity,
- [00:05:44.380]permanent melting point it's anything
that's left after it's anything that's
- [00:05:49.270]really stuck to the soil particles.
- [00:05:51.280]It's not going to be available
to the plants. So field capacity,
- [00:05:56.140]we, observed that anything,
- [00:06:00.590]any residue removal rate greater than
25% reduced plan available water outfield
- [00:06:05.540]capacity now permanent
wilting point or PWP.
- [00:06:10.010]And we saw no effect of residue removal,
- [00:06:12.500]but when we look at the
plant available water,
- [00:06:14.810]that was actually higher with
no removal than with 25% and
- [00:06:19.550]greater. Now you're
probably wondering, well,
- [00:06:21.890]why did we see these reductions in
plant available water when we are
- [00:06:26.810]removing residents? Well, if
you remember back a few slides,
- [00:06:29.720]we talked about particulate organic
matter and organic matter being lower.
- [00:06:34.670]That means that because those guys
are those two things are really
- [00:06:39.380]important for holding onto
water, as well as our,
- [00:06:44.120]aggregate structure.
- [00:06:45.380]field capacity is more driven by
organic matter and by aggregations.
- [00:06:49.720]So because both of those were
reduced with crop residue removal.
- [00:06:53.960]That's why we're seeing those
reductions. Now, thermal properties,
- [00:06:58.460]we're looking at three
different components here.
- [00:07:00.560]We're going to focus on the
first two thermal conductivity,
- [00:07:03.950]which is the ability of the
soil to conduct heat.
- [00:07:07.820]so it warms up on the surface.
- [00:07:09.530]We want that heat to transfer
down a little bit lower,
- [00:07:12.650]to warm up where a seed is
placed, specific key capacity,
- [00:07:17.930]which is the second column
of data. That's the,
- [00:07:23.210]amount of heat that it or energy that
it takes to raise the temperature
- [00:07:28.370]of a unit of soil. So in both cases,
- [00:07:33.050]we saw no effect of residue removal,
- [00:07:34.700]and I'll let Michael talk a little
bit more later about that. Cause he's,
- [00:07:39.080]he's got some contrasting data
based on some of his research,
- [00:07:44.510]and now we're going to
talk about crop yields.
- [00:07:48.170]And so we've got six years of crop yield
data out here. And in only one year,
- [00:07:53.030]did we see an effect of residue,
- [00:07:54.440]removal and residue removal
actually increased crop yields?
- [00:07:59.550]And the top line was 0% removal.
- [00:08:02.510]You can see it's 14.8
megawatts per hectare,
- [00:08:05.150]and then versus a hundred
percent removal at 16.2.
- [00:08:10.370]So what did we find? And in summary here,
- [00:08:14.270]particulate organic matter after three
years, no effect. After six years,
- [00:08:18.920]I rates of residue removal
reduced and by high rates,
- [00:08:21.620]I'm meaning at least 50%
overall, total organic matter,
- [00:08:26.390]no effect in year three, greater than
or equal to 25% reduced in year six.
- [00:08:32.090]what aggregate stability or soil
structure no effect in year three,
- [00:08:36.260]but after six years greater than or
equal to 50% reduced initial water
- [00:08:41.180]infiltration and compaction plan available
water and thermal properties were not
- [00:08:44.510]measured in year three. initial water,
- [00:08:48.440]infiltration and compaction.
We saw no effect.
- [00:08:52.130]We saw no effect of thermal
- [00:08:55.200]residue removal rates greater than or
equal to 25% reduced plan available water.
- [00:08:59.820]And after three years we saw that,
- [00:09:03.060]resident removal kind of
- [00:09:07.170]grain yields in one out of three years.
- [00:09:09.840]But then when we look at the
second set of three years,
- [00:09:11.910]we saw no effect of residue removal.
So what is our big takeaway? Well,
- [00:09:18.270]similar to other studies
and other regions,
- [00:09:21.600]we saw no effect of crop residue or we're
- [00:09:26.370]seeing mixed effects of crop residue
removal. And it's going to depend on,
- [00:09:31.410]on the residue removal, right? In general,
- [00:09:33.720]high rates of residue removal will have
negative impacts on soil properties,
- [00:09:39.240]but overall, we're not seeing a
lot of effects on crop yields.
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