Abstract
I
tested whether or not elevation
(tops and bottoms of hills) had an effect on the leaching of nitrogen
and
phosphorous out of the soil. The levels of nitrogen and phosphorous
found in
the soil showed that there was not a significant difference between the
tops
and the bottoms of the hills.
Introduction
Farmland is an important
part of our
environment and how the farmland is treated can change the soil.
Something that
is often done to the soil on farmland is that it is fertilized. This
increases
the amount of nitrogen and phosphorous in the soil. This is important
to the
farmland because nitrogen and phosphorous can change how well the
plants grow
and produce (Syers, Powlson, Sanchez, and et. al., 1997).
One of the issues that
farmers face
is being able to keep nitrogen and phosphorous levels up to support
their
crops. The challenge of deciding how much fertilizer to put on the soil
is
figured out by testing the soil for nitrogen and phosphorous levels.
This is
how the farmer decides what kind of fertilizer and how much fertilizer
the
farmer needs to put on the soil. If the farmer adds too much fertilizer
in the
soil, the possibility of the nutrients, nitrogen and phosphorous
leaching into
ground water becomes an issue. Even though it is important that these
nutrients
are present, it is also just as important that they are not present in
excess
because of the leaching and the dangers of the nutrients getting in the
ground
water.
This particular experiment
has been
designed to explore if leaching is affected by elevation (hills versus
bottoms
of hills). I hypothesized that because if leaching of soil does occur
and can
pull nitrogen and phosphorous out of the soil (Smil, 1991), that there
will be
higher levels of nitrogen and phosphorous at the bottom of the hill.
Materials
and Methods
On
October 14, 2007 around 12:00 p.m.
soil samples were collected off of Robert Poblocki’s Berwick farm on
Rural
Route 2, located in Illinois Warren County. A total of 20 samples were
collected. Ten of these samples were collected by locating areas on a
topical
map that were elevated. The other ten samples were collected by finding
a low
area in the vicinity of each elevated area located. Once there was a
total of
20 designated areas to sample from the samples were collected all in
the same
way.
How
I collected samples was by locating one of the designated areas and
digging a
hole .15 m depth to collect a soil sample from. The depth of the hole
that was
dug was figured out by using a Kenson 50 meter tape measure model
OTR50M to
measure. Then around the hole I first dug and sampled from I dug four
additional holes at .15 m depth to sample from using the same method of
measuring for the first hole. These four additional holes were dug at a
distance of 1.21 m, which was determined by the usage of Kenson 50
meter tape
measure model OTR50M. In addition, these four holes were located in the
cardinal directions with respect to the first hole dug and sampled. How
the
cardinal directions were determined was through the usage of a compass.
Once all
five holes were dug and sampled from the soil was mixed to make a
composite of
the soil and put in a glade zip block bag to be brought back to the
lab. This
same procedure was repeated for the 19 remaining designated areas.
Figure 1: This is how samples were collected for each of the 20 samples
Two
weeks later after the samples have been collected I tested the samples
for
levels of nitrogen and phosphorous. These tests were conducted through
the
usage of a Lamott brand model STH series combination soil outfit. The
protocol
for extraction procedure was followed along with the protocol for the
nitrate
nitrogen test and phosphorous test.
In
order to analyze data it was inserted into Microsoft Excel to get
means,
standard deviations, produce graphs, and to obtain p-values through
using a
paired T-test with one tail.
Results
The
nitrogen and phosphorous tests
that were conducted on the soil samples from both the tops and the
bottoms of
the hills indicated through statistics that there was no significant
difference
between the levels of nitrogen (Bottom of hill: Mean = 30.03 kg, S.D. =
14.92, Top
of hill: Mean = 35.94, S.D. = 11.39) (Fig. 2). Furthermore the p-value
for hill
tops and hill bottoms nitrogen levels is .1 this indicates that the
nitrogen
levels for the tops and bottoms of hills does not significantly differ.
Figure 2: Nitrogen
levels for hill tops and
Like the
nitrogen levels at the top and bottoms of hills the
phosphorous levels also do not significantly differ at the tops or
bottoms of
hills. This is not only indicated by the p-value of .17, but also is
indicated
by the mean and standard deviation (Bottom of hill: Mean 88.63, S.D.
7.18, Top
of hill Mean 90.9, S.D. 0) (fig. 3) indicating that the levels of
phosphorous
do not significantly differ from the hill tops and bottoms.
Figure 3: Phosphorous levels for hill tops and hill bottoms
Both the
results of the nitrogen and phosphorous tests
indicate that the levels of nitrogen and phosphorous do not differ
significantly. This refutes the hypothesis that I would find higher
levels of
nitrogen and phosphorous at the bottoms of hills due to leaching.
Discussion
According
to the results there was no difference in the levels of nitrogen and
phosphorous at the bottoms and tops of hills. This was opposite of what
was
expected. However, an explanation for the results could be due to the
fact that
rain fall was so small that leaching in the soil did not cause a
significant
difference in nitrogen and phosphorous levels (Wagenet,
Nye, Nowland,
and et. al., 1990).
Another explanation for why leaching may have not caused a difference
in the
levels of nitrogen and phosphorous levels is because the soil has been
used for
farmland for at least the last 9 years, which may cause the soil to be
so
saturated with phosphorous and nitrogen that leaching doesn’t cause a
significant change in the soil.
These
above mentioned factors that were not considered before doing the
experiment
would be a definite improvement and consideration for a follow up
experiment.
Literature
Cited
Syers K. J.; Powlson S.D.; Sanchez A.P.;
Greenland
J.D.; Ingram J. (1997, July). Managing Soils for Long-Term Productivity
[and
Discussion], Philosophical Transactions: Biological Sciences, 1011-1021.
Rtrieved October 1, 2007 from Jstor database.
Smil V. (1991, December). Population Growth
Nitrogen:
An Exploration of a Critical Existential Link. Population and
Development
Review, 569-601. Retrieved October 17, 2007 from Jstor database.
Wagenet R.J.; Nye P.H.; Nowland
J.; Burns I.G.; Greenwood D.J.; Addiscott T. M.; Graham-Bryce I.J.
(1990,
September). Quantitative Theory is Soil Productivity and Environmental
Pollution, Philosophical Transactions: Biological Sciences,
321-330.
Retrieved November 28, 2007 from Jstor database.