- Our first talk is by Amaya Atucha.
She's the Wisconsin Fruit Extension Specialist
and she's gonna be talking about the 15-year mulch study.
- Thank you, Sara.
I told her I really don't need any introduction.
I'm playing local this time.
The ones that don't know,
I'm the new fruit crop specialist.
I'd started a little bit more than a year ago.
And today, I have a talk on
some of my studies that I did
as a grad student when I was at Cornell
and the title of the talk, the real title of the talk
is Orchard Floor Management Systems
but Anna just put a little bit of her in the program
and she changed it but we're gonna be talking about
floor management systems today.
So I think they are recording us
so I'm gonna have to stay here.
There we go.
So just first, an acknowledgment,
all of the studies that I'll be showing today
I said it was part of graduate studies
and so, a big thank you to the Department of Horticulture
at Cornell that supported me as a grad student,
my adviser, Doctor Ian Merwin,
and technical support from Mike Brown.
Without them, I would have not been able
to do any of this work.
So just an introduction of why we are looking
and why floor management and soil health
which is that concept that we hear a lot is important.
First of all, (clears throat)
we know that it helps maintaining
just the soil fertility, the soil tilth.
It has an impact.
The way that we manage our soil and our orchards
has an impact on weed pressure and competition
for water and nutrients.
We all know with these new high-density systems,
how we talk about how it's very important
to control the weeds 'cause we want these tiny, little trees
to grow fast and to fill up the space.
Well, one of the reasons is because of our soil not nutrient
and water competition.
When we have a groundcover, we will have a mulch.
Also, we know that that is going to have an effect
on the soil temperatures and moisture extremes
so days are very hot
that soil probably is not gonna get that hot
and their root system is not gonna suffer that much
when we have a cover on our soil
than when we have our soil completely exposed.
Also, when we have specific groundcovers,
we can provide a habitat
for some beneficial insects and pollinators.
And very important, in certain orchards with slope
is to minimize soil erosion.
So what I'm gonna first present is a study.
It's a long-term study on the effect
of four groundcover management systems
that it did on an apple orchard.
And so, just the basic setting,
what we did is over 17 years,
we had four different ground management systems
that I'll explain afterwards
and we'll look at how the trees were growing,
the nutrition of the tree production
and we'll look at what was happening with the soil physical
and biological properties.
So here are the four treatments that we had.
We had a pre-emergence herbicide
in which the soil was completely bare.
We had no weeds.
Nothing was growing underneath the trees.
We had a post-emergence
that you can see some weeds going on here.
We had a mix of post-emergent herbicides.
It was mainly glyphosate.
We would apply twice during the growing season, early in May
and then we would apply it again around July, August
and so, some weeds would grow
but during the times that we would apply the herbicide,
the weeds would die.
Then we had a sod treatment
that it was just basically the continuation of the
(clears throat) sod that we had on the alleyways.
We just planted the same sod underneath the trees.
And then we had a mulch treatment
that was right underneath the trees in the same,
all of these in the same area
and that we would renew every other year.
And so, a little bit more specifics about the treatments.
The variety that we had,
this was an Empire on an M9, M11
planted in 1992.
It was a three by six meters.
That was the planting frame
and we had as I said the four treatments.
The PreHerb, the mix of pre-emergence herbicides.
The PostHerb which was basically glyphosate
as I say in May and July.
The Mowed Sod which was a mix of just orchard grass.
And then we had the mulch,
it was a hardwood bark mulch
composed of all these different species.
And I said the orchard and the treatment
were established in 1992 and were maintained since then.
So what did we see
during the time that we measure?
And we'll look at these different treatments.
So when we look at tree growth,
you can see here the cumulative tree cross-sectional area
in centimeters so it's basically the area of the main trunk.
So from 1992 all the way to 2008, we measured this
and everytime you see this asterisk here,
it means that there is a statistical difference.
So you can see in the very first year,
the blue and the red, so the first two columns
are going to be the herbicide treatments
then the green one is the grass
and then the black one is the mulch.
So what we saw is that during the first year,
we saw some significant difference.
With no surprise, the herbicide treatments,
those trees were bigger
so the first maybe four years,
we saw that there was a significant difference
in favor of using the herbicides.
Trees were bigger.
But as we move on
and that's where these studies are so interesting,
we start seeing that there's a shift
on tree growth and we started seeing that the mulch,
actually the trees on the mulch are much bigger
and is statistically different
from all the other treatments.
And what we get by the last year,
we can see how the mulch trees
are significantly bigger than all of the rest.
And we can see actually, that is the tree
in the PreHerb or the pre-emergence herbicides,
the treatment that was bare soil.
Those trees are significantly smaller than the rest
especially than the mulch
which was very different from the trend
that we saw the first four, five years.
So this is very interesting
because most of the studies that we do
in orchard systems, we usually do four, five years
and we're like, "Wow, that's a lot of years."
Well, this shows that there are significant changes
in trends when you keep measuring
things like different treatments of groundcovers
or different soil management systems.
So when we look at,
we excavated one tree
and we decided to divide it and look at
what was the weight of the main trunk,
of the main roots, of the secondary roots,
and of the fine roots
but we also look at if there was any difference
in the trees itself in terms of the size of the trunks,
the main scaffolds,
The three-plus-year branches, the two-year branches,
and the one-year branches so when we look at these,
we actually didn't see a lot of significant difference.
This was 10 years after the treatments were established.
What we mainly saw was a different
on the secondary roots.
We saw that it was actually in the treatment
that has the glyphosate applied twice
during the growing season.
We saw in that one and the mulch
a little bit more roots than on the sod
and on the bare soil treatment,
and this is probably due to competition also.
It might be possible in the sod
that there were less secondary roots
because of competition with the sod itself
but in the case of the pre-emergence herbicide
where we started seeing at this time
and if you remember the previous graph,
the tree started to decline in term of growth
and so, what probably we're seeing here
is that the sod properties are starting to deteriorate
and that is affecting the development of the root.
When we look at yield,
here we have the kilograms for tree...
starting from 1994 all the way to 2008,
again, we see that in the very first years
is actually the two herbicides
so that the first two columns, that had the highest yield
which, you know, it makes sense.
We had bigger trees.
They had bigger trees of higher yields
at the very beginning
but then once again, we started seeing that
there's a lot of shift.
There's some years that we had spring frost
so that's why you see this very low yield here
but we see that overall, after 17 years,
there's not really a clear significant difference.
You can see some trends.
You can see that the mulch still produces
consistently higher than the bare soil treatment
and is actually the PostHerb
so the glyphosate applied twice a week
letting some of the weeds grow
that is very comparable to the mulch
so once again, this illustrates that what happens
at the very beginning
might not be what we see in a mature orchard afterwards.
So what happens with soil fertility?
I know there's a lot of data here
but I just want to point out some very specific things.
We measured here, we have 1992, '93, '95,
2000, 2005, 2006, and 2007.
So by 2007, one of the biggest difference
is that if we look at the phosphorus,
a significant different mulch had
10 times more phosphorus in the soil.
The same if you look at calcium,
how much higher and significantly higher mulch is
after those 17 years.
And then the pH, we see some difference
also in the pH.
We tend to have a little bit higher pH
on the mulch which was significantly different
and we see some difference, significantly difference
on the magnesium.
So what happens that over time,
that mulch that we kept putting on and putting on
and putting on started decomposing and releasing
a lot of these nutrients
that just the bark of those trees had
and thus, those were probably not available
at the very beginning when we saw
almost no significant difference
but after 17 years of putting more and more
and more mulch, what we saw is every time
we would excavate the soil
is this baked layer of like dark, dark organic matter,
decomposed organic matter full of roots,
all the roots were there.
Well, no wonder, with all of those nutrients there
and being moist and cool,
of course, their roots wants to grow there.
When we looked at the carbon in the soil
and the nitrogen and carbon-to-nitrogen ratio
which is a good indication of microbial activity,
we saw that the percent of nitrogen in the soil
was significantly higher once again in the mulch
with no difference on the other three treatments.
When we look at the carbon, again, it's the mulch
after those 17 years that it has, even before that,
by '99, so seven years
after the treatments were established,
already the mulch treatment was significantly higher
carbon content and the carbon-to-nitrogen content
again was significantly higher for the mulch
and there were no significant difference
between the other treatments.
Some soil physical properties,
some of the things that were measured by Oliveira
in the same study, by eight years after the treatments
were established is that you can see
that the mulch treatment has a significantly lower
bulk density so that soil was looser
and more fluffy and nicer soil.
We also see there's difference in the infiltration rate
of the water and the soil capacity
so that soil had a significantly higher
water holding capacity.
It had the capacity of keep more moist in that soil
than the other treatments
especially than their pre-emergence treatment,
the treatment that had bare soil
which we saw a little bit of compactation on the very top
so a lower infiltration rate.
This graph here
shows soil biological properties
so it's showing microbial activity in the soil
which is very important for mineralization as you know
and so, on the very top, it shows soil respiration.
It's a good indication of how much activity that soil has,
how much microbial activity is happening
and so, you can see,
this is a work done by Yao in 2005 in the same orchard,
you can see that the mulch here,
the first line with the Xs is significantly higher
in terms of soil respiration than the other treatments.
When we look at the number of bacteria,
so in the colonies, the number of colonies of bacterias
forming the soil, we see that the mulch
also has significant and the PreHerb, the bare soil,
very, very low bacteria activity
and this counters for pathogenics and beneficials.
And for fungi, once again, surprisingly,
it's actually the grass that has a very significant,
higher content of colonies of fungi in the soil
compared with other treatments
that were not significantly different
so bottom line, we can see that the pre-emergent herbicide
had a very, very low microbial activity on those soils.
So just a couple of summaries of these studies.
First, the total soil nitrogen, carbon content
and the ratio of carbon-to-nitrogen
are essential for plant and nutrients
and were much higher in the mulch treatment
after 16 years than on the pre-emergence treatments
or the bare soil treatment.
We saw that in the weed-free plots
so in the pre-emergence herbicides,
most of the soil physical properties
and biological activity was deteriorated.
We saw that soil was much more compacted.
It holded less water.
It also has less roots and there was less microbial activity
and it was actually the post-emergent herbicide
so that glyphosate applies twice during the growing season,
letting the weeds grow during the rest of the growing season
which produced the best results in terms of compromising
of soil fertility, soil microbial activity
but also in terms of fruit production.
That is what we are very much interesting.
This is very nice but if we don't produce any fruit,
it doesn't work.
So the second study that I'm going to present today
is a study in which
we look at the entire system.
We wanted to know,
given that we have all of these treatments...
what happened with the nitrogen budget?
What happens with the nitrogen in the system
once you have a groundcover management system
established for so long?
So the objectives were, mainly,
we were concerned about pesticides and fertilizer,
excessive use and leeching into the groundwater
which was a problem that we had in upstate New York
so the idea started from there.
We wanted to try to look,
"Well, if we treat the soil differently,
"we manage our weeds differently,
"can we affect the overall nitrogen budget
"of the sod of the plant
"given that we have all of these previous information?"
So we quantified the inputs and the outputs
of nitrogen in the orchard
with these four different treatments
which are going to be the same treatment.
In one year in which we apply fertilizer
and in a year in which we did not apply any fertilizer
so in the year that a fertilizer was applied,
53 pounds of nitrogen per acre were applied.
So again, the same treatments,
two years: a year with fertilizer
and a year without fertilizer.
So what did we see? Or how did we measure it?
This is our little budget
so we look at everything
that was adding nitrogen to the system:
the fertilization, all the nitrogen
that was coming from the irrigation
and precipitation water,
and the nitrogen that was being mineralized
from the bark mulch,
from the treatment that had the mulch.
We look at everything that had internal fluxes
so all of the nitrogen that was being used
and coming back to the system,
just in the surface, all those weeds,
all the grass, we would basically clip that grass
and the grass would stay there,
decomposed, and the nitrogen would just go
from the grass to the soil, from the grass to the soil, and it would stay there.
We measured that.
We measure how much nitrogen was being recycled
through the leaf litter, through the pruned wood,
and we calculated how much nitrogen
was coming out of the soil.
Then we look at the outputs,
how much nitrogen we were taking out of the system
through the fruit and all the nitrogen that was going out
through the water that was leeching all the way out
of the orchard and the surface runoff water
that had also nitrogen.
So just to show you more or less how we did these things.
So this is how we measure all the nitrogen
that was coming out from surface vegetation.
We had these litter bag studies
in which we would clip some of the vegetation on top,
put it on these special bags,
and measure over time from day zero,
how much nitrogen they had until several days afterwards
to see how much of the nitrogen
had been decomposed by the microbes in the soil
and going back to the soil
so that's how we measure that.
One second.
This is how we measure the amount of nitrogen
in the leaves so what we did is we chose one tree,
we put a big net, we cut all of the leaves
from those trees, we dried them, we measured them,
and we took a sample,
and we analyzed how much nitrogen it had
so that's how we measure how much nitrogen
there is in the leaves
which was a lot of work.
And then we measure the outputs.
Fruit, very easy,
of course, we measure every single fruit that we had.
We took a sample and we analyze how much nitrogen was there
so that we can take it out of the budget.
The subsurface leeching,
what we did is we had this system
in which each one of the plots,
these are each one of the plots, we had 12 plots,
was hydrologically isolated
and we had some pipes,
some drainage pipe that would capture all of the water.
It was probably three to four feet under the ground
and it would take us to these stations
in which we could collect some water there
and we had a little system of some tipping buckets
that were connected to a data logger
so all of the water that was infiltrating the soil
was being collected on these pipes
and being driven to these tipping buckets
that you can see here
that when they're full, they switch,
they flip like this and so,
you know the exact volume of water that you have in there
and so, if you have the number of tips,
you know how much water run over
when there was a storm or when we irrigate it,
we could calculate that
and we would take periodically samples of that water
and analyze how much nitrogen it had.
And so, then we calculated all of the nitrogen
that was lost through the leeching
so the water that was infiltrating the orchard.
In a very similar way,
we measured the water that was exiting the orchard
through surface runoff.
We had a system in which we had half a pipe
on the bottom of this plot
and it would collect all of the water
running from the surface
and it would once again go to a tipping bucket
and then we would do the same as we did with the leeching.
So what did we see?
You can see on the graph on your left side
is an F for the year that we fertilized it with nitrogen
and NF for no fertilizer
so here, what we have is the amount of nitrogen
that was being mineralized from what was growing
just on the surface of the soil
so here are the grams of nitrogen per kilogram biomass
so this is those little packs that we had
that we put these litter bags that we put
and we can see that in the year
that we applied fertilizer,
these solid squares here
show the mulch.
It shows how the mulch mineralized much more nitrogen
so that vegetation, those weeds that were growing
in the mulch had a lot of nitrogen
and if you cut them down and you let them mineralize,
they were going to put a lot of nitrogen in the system.
The year that we had no fertilizer,
we still saw that the mulch was the one
that was releasing the most nitrogen
from that surface vegetation.
Just because the mulch was also given nitrogen
to the system so if you had the weeds growing
where there was a lot of nitrogen,
well, those weeds contain a lot of nitrogen as well.
When we look at the average concentration of nitrogen
that was coming out of the runoff water,
you can see that in the year with fertilizer,
here are the treatments.
The treatment with bare soil had the highest concentration
of nitrogen exiting the system through runoff.
While the year that,
when we look at the leechate,
we actually saw that it was the mulch
in both year that has significantly higher nitrogen
exiting the system so what this means is basically
there was more nitrogen coming out through runoff
on the bare soil because the bare soil,
as I was showing before,
had lower infiltration of water.
The water was just running off
instead of coming in because there was this crust
that formed because we had had it exposed for so long.
It had nothing to protect it
while the mulch, there was a lot of water
actually infiltrating the mulch
because it had a much higher porosity,
the water would go into the soil
and it would drive all of this nitrogen
coming out of the mulch after 17 years
and that's why we saw these really high concentrations.
And so, when we look at the water flow,
once again, we see that the mulch
had the lowest amount of surface runoff
because all of the water was infiltrated
but it had the highest level of leeching water
because more water was coming in
and going through the soil profile
and then exiting to the groundwater.
So, again, this is a lot of data
but what I really want to show
is up here, there are all the treatments:
the bare soil, the glyphosate, the sod, and the mulch.
And here's the budget, you can see this is the everything
that was exiting,
all the nitrogen that was exiting the system
out of the orchard,
all of the internal fluxes, and all of the outputs.
So you can see here the mulch,
it has a significantly higher input.
There was a lot of nitrogen going into the system
when we had a mulch,
either basically from the decomposition of the mulch.
When we looked at the balance
which is basically if you add what you take out,
sorry, what you put in weed where it was being recycling
and you subtract what you're taking out,
overall, what we saw is that the year that we had fertilizer
so it's the first column for each one of these:
the 20, 10, 43, and 187,
they were all positive
which basically means that orchard
had more than enough nitrogen.
The nitrogen that we were putting in with the nitrogen
that we were taking out, it was a positive result.
There was extra nitrogen
than what the orchard really needed.
But the year in which we apply no fertilizer,
you can see that both of the herbicide treatments
have negative number.
It means that there was more nitrogen being lost
in that orchard so there was not enough nitrogen.
But with the groundcover and with the mulch,
the year without fertilizer is still positive
which means that those systems, after 17 years,
in a way, they had equilibrated
and they were given enough nitrogen
for those trees to grow,
to produce and there was less nitrogen being lost
out of the system and this happened after 17 years
of those treatments.
Okay, I only have three more minutes
so we're gonna go fast through the summary.
The soil nitrogen that was mineralizing and recycling
so basically everything that was coming from the leaves,
from the pruning, from the surface vegetation,
all of that accounted for over 60%
of the nitrogen that was being recycled.
The harvested fruit represented more than 70%
of the nitrogen that was coming out of the orchard
so even nitrogen was coming out through runoff
and through leechate and through the fruit
that we were harvesting,
70% of the nitrogen was coming out with the fruit.
Most of the nitrogen's losses occur through leechate
rather than runoff so this was a big eye-opening for us
because it meant there's a serious potential contamination
of groundwater because a lot of the nitrogen
was just being leeched out of the system.
As I said, there were positive balance overall
for the sod and the mulch
but it was not the case for the herbicides.
And potential long-term problems with the nitrogen leechate
in the orchards
that made us think that maybe if you are applying
organic amendments like compost
or you're using mulch or you're using any other source
of organic nutrient that you should be cautious
about how much you put in and how often you're putting it
because you might ended up what would happen with us
with the mulch, that that mulch was being mineralized
and there was so much nitrogen coming out of that
that there was a lot of nitrogen going into the groundwater
which is a big problem.
And overall, after 17 years,
the system was not balanced for the two herbicides
and we saw that the main reason was that the
recycling of the nitrogen was much lower
when we were having an herbicide
compared when we had the grass
or when we had the mulch.
So with that, I think that I'm running out of time.
I'll be happy to take any questions.
No, it was clay. It was mainly clay.