So my name's Lisa Eash.
I'm a PhD student at Colorado State in the Department of Soil
and Crop Science.
And I'm looking at cover crops as a potential solution
for soil health restoration in dryland cropping systems
on the Colorado Plateau.
So I actually do my research in Yellow Jacket in Colorado.
But we work with farmers that extend
into San Juan County in Utah.
So I guess we're all familiar with the Colorado
Plateau and the little annual precipitation that it receives.
Many farmers in this region also don't have access to irrigation
and rely on dryland farming, which
is why we're all in this session and why
we care about dryland farming.
And as a result, many farmers rely
on a 14-month fallow period in between cash crops
to recharge soil moisture and take advantage
of the low amounts of precipitation
that the area does receive.
So over time, this has led to a lot of soil erosion.
And now we're in a situation where soils are
highly degraded in the area.
So our project is exploring cover crops as a potential way
to mitigate a lot of the challenges
that local farmers face.
In other regions, cover crops have
been shown to have several benefits, which
seem to directly address a lot of the challenges, some
of which are providing soil cover to prevent erosion.
Cover crops can increase soil organic matter levels
or fixed nitrogen in the case of planting legume cover crops.
And they also have mentioned the increased soil water retention.
So in the monsoon season, like we're in right now,
the soil could actually capture more rainfall
and have less runoff.
But they also imply an increase in water consumption
because cover crops take moisture to grow.
And you limit the amount of soil moisture recharge associated
with the fallow period.
So that could represent a trade-off and a barrier
to the adoption of cover crops in a semi-arid region
like the Colorado Plateau.
So we aim to evaluate how cover crops impacts soil
health in such an arid climate.
They've been studied in more humid regions
like the Northeast or the Great Plains, so we want to see,
in a more moisture-limited environment,
how they impact soil health.
And I want to evaluate what the trade is in terms of cash crop
productivity and whether cover crops are economically
viable in this area.
And we want to share these results with producers
and local stakeholders to gain feedback
on cover crop perception and eventual adoption.
So we're doing this through a three-pillar approach.
We have ongoing experiments at the Southwest Colorado Research
Center where we can employ a factorial experimental design
and look at how specific management
practices, like planting window, cover crops species,
and tillage regime can influence the impacts of cover crops.
We also work with farmers throughout the Colorado Plateau
who implement cover crops on a portion of their field
and are asked to just continue with their typical farming
practices.
And that is with the intention of seeing
how cover crop results apply to more of a real-world setting.
And then we get consistent community feedback.
And that's important in ensuring that our results are actually
pertinent on a local level.
So we have two experiments on station.
The first was started back in 2015.
And it looks at three different fall-planted mixtures
against fallow wheat treatment, which is the control.
And we have three replicated blocks.
And this is all under no-till management.
And so, again, this was started in 2015.
So we're just coming out of our third cover crop rotation.
The second experiment is a little more in depth
and was started a year later.
It compares five fall-planted and three
spring-planted mixtures against a wheat fallow control.
And we're also looking at how no-till versus
conventional tillage impacts the effects of cover crops.
Here, I show just one block of the experiment--
so all nine cover crop treatments,
and then we have a split-plot design separating
conventional and no tillage.
And that's replicated three times.
So we're just coming out of the second wheat rotation.
So like I mentioned, we also work
with participating dryland farmers
throughout San Juan, Montezuma, and Dolores Counties.
So they plant cover crops in replicated strips
on their field.
And then their practices span a wider range.
Some producers are no-till, some are organic.
They plant different cash crops.
And then, we go in and take yield biomass and soil health
data over time.
So this project goes through 2021.
So these are just some of the preliminary results.
These results are from the second experiment
that I showed you where we're looking
at spring-planted and fall-planted mixtures.
So fall-planted mixtures are producing
about four times the amount of biomass as
compared to the spring-planted mixtures.
So within those planting windows,
cover crop species selection doesn't
look like it has much of an effect on overall cover crop
biomass.
And a big reason for that is that,
in the fall-planted mixtures, species are actually
being outcompeted by volunteer wheat and weeds in many cases.
And then, this is reflected in subsequent wheat fields
where the wheat and the fallow treatments
is yielding significantly more than
in the fall-planted treatments.
And then spring planting treatments
are yielding somewhere in the middle.
And so, when you actually correlate
the cover crop biomass with the subsequent wheat yield,
there's a pretty nice linear regression
with an r-squared of 0.53.
So there's a pretty significant relationship
between cover crop biomass and the subsequent yield penalty.
So this could be a way for, if you wanted some of the benefits
in terms of soil health or maybe just soil cover,
you could consider planting later in the spring,
or you could terminate earlier and then have
less of a wheat yield penalty.
So what is causing the wheat yield
penalty following cover crops?
So as we know, moisture is the primary limitation
in the region.
So it's not a surprise that we're seeing decreased soil
moisture with the cover crops.
Particularly, in the fall planting
cover crops, which is mixes one and five, shown on the left
here, you see much lower soil moisture
throughout the soil profile.
And then, the spring-planted mixtures,
which are the blue and green lines,
are in between the fall-planted in the fallow.
And we're also seeing a reduction
in available nitrogen. So this is measured at 2017 wheat
planting and is showing how much nitrogen is actually
available to the wheat, since a lot of dry land wheat farmers
don't fertilize in this region.
So a lot of nitrogen is being immobilized in the cover crop
biomass.
So you see a lot less soil nitrate
in the fall-planted cover crops, which are shown in red,
than you do in the fallow, which is shown in green.
But it's important to note, of course,
that this isn't a loss of nitrogen from the system.
And this will be mineralized back into the soil eventually
and, perhaps, in a timely way that
could be beneficial to the wheat in the future.
And so since these are dryland systems,
cover crop biomass is usually very
dependent on the year in which it's grown
and particularly, the precipitation amounts
and distribution patterns.
So in 2016, we got really good cover crop biomass,
between 4,000 and 5,000 pounds per acre,
which is definitely a significant amount.
But then, in 2018, this was following
a severe drought in the area.
And so we were only averaging a little more than 1,000 pounds
per acre.
So this is reflected then in the wheat yields
where there was a 25% wheat yield penalty following
all that cover crop production.
And then, in 2019, there actually
wasn't a wheat penalty.
And the cover crop treatments actually
yielded slightly higher even than the fallow, which
is shown in the purple bar.
So we're seeing similar trends on farm too.
So in 2016, farmers, similarly, have
a lot of biomass production.
And so they also saw, on average, a 25% reduction
in wheat in the cover crop plots.
And this is averaged across all of those farm sites
that I showed you in the map.
And then, in 2019, this was following very little
to cover crop biomass production.
So you see a slight reduction in wheat yield,
but the differences are not significant.
So we're also monitoring soil health metrics.
And we know that changes in soil health
take several cycles to show up and, particularly,
in arid regions.
So we still have yet to see significant changes.
In experiment one, which was started a little bit earlier,
and it's going through two cover crop wheat cycles now,
we're seeing trends.
So this is showing total soil carbon.
And it's slightly higher in cover crop treatments.
It's significant to an alpha level of 0.1.
But we're just going to continue to monitor this over time
and see if the changes become more pronounced.
And this is soil aggregation.
This is showing in wheat diameter and the cover
crop versus the fallow.
And again, there's a trend, but this is not yet significant.
So the project is going to be followed through 2021 at least
with possible extension.
And so we're just going to see whether, over time, the soil
health improves and whether that's enough for farmers
to justify taking a little bit of a wheat yield
penalty in the shorter term.
So with that, I'll take any questions.
Thanks a lot for your attention.