Kristina: Hello, plant scientists.
Today we're going to learn about Dr. Sam Wortman
and a study he conducted on biodegradable plastic
and fabric mulch performance.
So we're going to learn a little bit about Dr. Wortman,
we're going to learn about the study he conducted,
and at the end, we're going to look at some data
he collected and how we can read that data.
So Dr. Sam Wortman is an assistant professor
at the University of Nebraska-Lincoln
and he focuses on environmental horticulture.
His interest is in local, urban,
and organic vegetable production,
and he's studying biomulches
because they can be used as alternatives
to polyethylene mulch,
which is commonly used in vegetable production.
And growers are concerned
about the disposal of polyethylene film
and are seeking alternatives that provide the same benefits,
and so that is why he is conducting this recent.
So growers use polyethylene mulch
because it helps control weed growth,
it increases yields,
it helps with temperature management,
it has a low cost and it helps improve growth.
And it's an environmental concern
because it has to be removed and disposed of
after each growing season.
The most common way it is disposed of
is by being stockpiled on farms.
There are options to recycle it, but they are very limited,
and hauling it to a landfill is very costly,
and burning isn't an option because they are carcinogenic.
Alternatives to polyethylene mulch are organic mulches,
paper-based mulches, bioplastics and biofabrics.
But bioplastics and biofabrics were used in the experiment
because previous research that was conducted
shows that they have the greatest potential
to be an alternative.
So seven treatments were used in the study.
Bare soil was used as a control to compare six biomulches,
and of the six biomulches, there were four biofabrics
that varied in thickness, weight, and color,
and highlighted in the yellow box
there are two bioplastics.
From 2013 to 2015 at the University of Illinois
in Urbana, Illinois, the experiment was conducted.
A total of five trials were conducted
over that span of time,
and you can see in the photos
that each trial was arranged as a randomized block design
with four replicate blocks.
In 2013, you can see in the photo on the left
was the cucumber trials, and that had two trials,
one in the field and one in high tunnels.
In 2014, which is the photo on the right,
again, two trials were conducted,
one in the field and one in high tunnel
using tomatoes and peppers.
And in 2015, only one trial was conducted
in the field using cucumbers.
So what type of data did Dr. Wortman collect?
He collected data on soil temperature, soil moisture,
weed emergence, crop yield,
decomposition of biomulches in the soil,
and mulch deterioration.
In a few slides we are going to look at data,
and the data that we are going to look at
will be from the 2013 cucumber field trials
for the decomposition of biomulches in the soil.
So we need to learn how the data was collected.
So the biomulch was incorporated into the soil
after each growing season,
and it was incorporated into the top 15 centimeters
using a rotary tiller.
And you can see in the photo
the biomulch before and after incorporation into the soil.
After the mulch was incorporated into the soil,
it was then sampled at zero, six, and 12 months.
And to get the samples, a golf hole cutter,
which you can see in the photo,
was used to remove eight core samples per plot at random
from each experimental unit.
The soil samples once collected
were then sieved to recover mulch residues
and then recovered mulch
was then washed, dried, and weighed.
So now we have background information
on the experiment conducted by Dr. Wortman.
So let's think, if we conducted this study,
and in our cucumber field trial for 2013
for the decomposition of the biomulches in the soil,
here is data for two of the biodegradable fabrics.
This is what you would be looking at.
And so here is BK-1-270,
and below it is BK-2-360, my two biofabrics.
I have the four replicates for each,
and I have their mass of the remaining biomulch in the soil
at zero, six, and 12 months.
So we're writing our article and we want our reader
to be able to easily look at this data
and understand what is happening.
So to easily compare the biofabrics
at zero, six, and 12 months,
the first thing that we want to do is create a graph.
And so to create the graph,
we wanna take the averages of each replicate
for each treatment at zero, six, and 12 months,
and so we're going to find our average.
So we're going to start by finding the average
for our biofabric BK-1-270.
And so to find the average,
and the average is also considered the mean,
we're gonna take the sum of the data,
so step one, sum up all data points.
So we're gonna add up at for zero months
each mass for each of the four replicates.
So down here, you can see that I've done that
and I come up with 317.58.
And then because we had four replicates,
I'm going to divide that number by four
and I get my average.
And I will do that for six and 12 months
and I will do that for my other treatment as well.
So now that I've calculated my averages
for both of my biofabric treatments
at zero, six, and 12 months,
I'm going to take this data
and put it into Excel to create a graph.
So I created a bar graph in Excel from my averages.
So I have a graph
of the average biomulch remaining in the soil.
And as you can see, my biomulch treatments,
I have BK-1-270 and BK-2-360.
And I can easily compare them,
the blue being immediately after incorporation,
the orange is six months after incorporation,
and the silver is 12 months after incorporation.
So I can easily see what's happening during that timeline
and it's also easier for my readers
to understand what is happening.
And there is more that we can do to understand the data
for the decomposition of biomulch in the soil,
but we are going to save that for a future lecture.