NOTES
Use of a dichotomous key
as an aid to correlating
soil series
Steven M. Jones and Bill
R. Smith*
Abstract
Traditionally,identification of soil taxa is accomplished
by
repeated comparisonof morphologicaldescriptions. This
cumbersome
andoften confusingprocess can be facilitated by
a systematicapproach
suchas usingdichotomous
keys. Theconcept of usinga dichotomous
keyto correlatesoils at the series
level is demonstrated.
Six dichotomous
keys weredevelopedfor
the Blue Ridge Mountainand PiedmontPhysiographicProvinces in SouthCarolina,primarilyas taxonomicaids in conductingforest soils research.However,
they haveprovento be
invaluableinstructionalaids as well.
T
O THEPLANT
TAXONOMIST,
identification of unknown
plant and tree specimens would be tedious and time
consuming without the aid of a dichotomous key. The
dichotomouskey includes those characters that differentiate taxa and omits those descriptive characters that are
nondifferentiating.
The obvious advantage lies in the
ability to identify taxa without repeated comparison of
lengthy morphological descriptions. This approach not
only facilitates identification of unknowntaxa whenthey
are first encountered, but also serves as a quick reference
when distinguishing amongfamiliar but confusing taxa.
Wehave applied this concept to correlating soil series.
The TaxonomicKey to Soils
In a stepwise progression, a series of choices is offered
to the user. At each step, one of two statements is chosen
that best describes the unknownsoil series. The user is
then directed to the next pair of statements. This procedure is continued until the soil series nameis reached.
Since these keys are intended for field use, differentiation requiring laboratory procedures is not included;
therefore, more than one series name is given when taxonomic separation based on field characteristics is not
possible.
To avoid the complexities of a single, large key, the
44 soil series were classed into two groups based on landS.M.Jones, Dep.of Forestry, ClemsonUniv., Clemson,SC29634;
and B.R. Smith,Dep.of Agronomy
and Soils, Clemson
Univ., Clemson, SC29634.Received25 Sept. 1987.*Corresponding
author.
Publishedin J. Agron,Educ.17:128-129
(1988).
128
J. Agron.Educ., Vol. 17, no. 2, 1988
Table1. Subdivisionof landscapepositionsandphysiographic
prw
vinces andthe corresponding
taxonomickeys.
Keys
toupland
soils
Blue
Ridge
Mountain
Province:
Chauga
Ridges
Region
Key1
BlueRidge
Mountain
Region
KeyI
Piedmont
Province:
Piedmont
Foothills
Region
Upper
Foothills
Key2
Lower
Foothills
Key2
Midlands
Plateau
Region
Interior
Plateau
Key2
Charlotte
Belt
Key3
Carolina
Slate
Belt
Key4
Southern
Piedmont
Hills
Key3
Kings
Mountain
Region
Key4
Keys
tobottomland
soils
Blue
Ridge
Mountain
Province:
Chauga
Ridges
Region
Key5
BlueRidge
Mountain
Region
Key5
Piedmont
Province:
Piedmont
Foothills
Region
Key6
Midlands
Plateau
Region
Key6
Kings
Mountain
Region
Key6
scape position. The two groups were defined as upland
soils weathered in residuum and bottomland soils formed
in alluvium. In addition, within each landscape position
class, soils were grouped by physiographic division, and
a separate key was developed for each region (Table 1).
This hierarchy of keys reduces the number of decisions
required by the user. One of the six dichotomous keys
developed for the Blue Ridge Mountain and Piedmont
Provinces in South Carolina is illustrated in Table 2.
Discussion and Conclusion
The taxonomic keys were informally developed and
tested over a 5oyr period to aid in soil series identification while conducting forest soils research. During this
period they were found to be useful as instructional aids
in teaching field taxonomy to undergraduate and
graduate students. Typically, students in forestry and
agriculture are familiar with the mechanics of working
through taxonomic keys. Students are introduced to the
soils keys by correlating typical pedonsin the field. This
systematic approach allows students to understand more
readily the concept of the series being viewedas well as
the relationship to closely related taxa. In addition,
students are not overwhelmedby what seems to them to
be an impossibly large number of soil taxa with which
to become familiar.
Successful application of the keys has been verified by
colleagues engagedin research. In those disciplines where
soil taxonomyis a research tool rather than an end in
itself, it is commonlybelieved that learning to identify
soils would be much too time consuming and bothersome.
The concept of the taxonomic key alleviates this "fear
or the unknown."Often, after introduction to the keys,
Table 2. Key to upland soils in the Piedmont Province.
Key 2. Piedmont Foothills Region
Upper Foothills Subregion
Lower Foothills Subregion
Midlands Plateau Region
Interior Plateau Subregion
1 Surface soil has silt loam texture
1 Surface soil has sandy loam texture
2 Soils with clay, clay loam, or sandy clay loam subsurface (argillic) horizon (Ultisols)
2 Soils with no increase in clay in subsurface, texture
sandy loam throughout (Inceptisols)
3 Subsurface "hue" 7.SYR or yellower
3 Subsurface "hue" SYR or redder
4 Solum depth < 100 cm (40 inches)
4 Solum depth > 100 cm (40 inches)
5 Subsurface (argillic) horizon has clayey texture (clay
>35%)
5 Subsurface (argillic) horizon has fine-loamy texture
(clay <35%)
6 Gray mottles present in the subsurface (argillic)
horizon
6 Gray mottles not present in the subsurface (argillic)
horizon
7 Solum depth 50 to 100 cm (20 to 40 inches)
7 Solum depth < SO cm (20 inches) (mica common)
8 Mica common to abundant throughout the pedon
8 Mica not common to abundant
9 Subsurface (argillic) horizon clayey (>35% clay)
9 Subsurface (argillic) horizon fine-loamy (<35% clay)
10 Color "value" in subsurface (argillic) horizon <3
(dark red)
10 Color "value" in subsurface (argillic) horizon >4 (red)
11 Solum depth <100 cm (40 inches)
11 Solum depth >100 cm (40 inches)
12 Solum depth <50 cm (20 inches)
12 Solum depth 50 to 100 cm (20 to 40 inches)
13 Solum depth 100 to 150 cm (40 to 60 inches)
13 Solum depth >150 (60 inches)
14 Subsurface (argillic) horizon <60 cm (24 inches) thick
14 Subsurface (argillic) horizon >60 cm (24 inches) thick
15 Subsurface (argillic) horizon <30 cm (12 inches) thick
(mica common)
15 Subsurface (argillic) horizon 30 to 60 cm (12 to 24
inches) thick
16 Mica common to abundant throughout the pedon
16 Mica not common to abundant
17 Subsurface (argillic) horizon fine-loamy (<35% clay)
17 Subsurface (argillic) horizon clayey (>35% clay)
18 Subsurface color "hue" 2.5YR or 10R
18 Subsurface color "hue" SYR or yellower
19 Firm, brittle layer at 38 to 100 cm (15 to 40 inches)
19 No firm, brittle layer present
20 Mica common to abundant throughout the pedon
20 Mica not common to abundant
21 Subsurface color "hue" 2.5YR or 10R
21 Subsurface color "hue" SYR or yellower
22 Rocky soil with a discontinuous loamy subsurface
(argillic) horizon
22 Soil not rocky and does not have a discontinuous
loamy (argillic) subsurface horizon
Use key 4
2
3
22
4
10
7
5
6
Durham
Helena
Appling
8
Tallapoosa
Grover
9
Wedowee
Rion
Bulletin (Jones and Smith, 1987). Use of technical terms
was avoided as much as possible, allowing those with a
limited knowledge of soil taxonomy to use the keys, particularly after some field experience. Some knowledge of
technical terminology is necessary, particularly in describing soil color. Users must be familiar with Munsell soil
color charts. A small glossary of technical terms accompanies the keys to aid in their use. In addition, a brief
description of all the soil series listed in the keys is
included.
The dichotomous key format has proven to be efficient
as a means of correlating unknown soil series and as a
quick reference for differentiating familiar but taxonomically confusing series. Application of the taxonomic keys to the classroom has also been effective. For
more advanced students, a higher level of soil taxonomy
terminology normally accompanies instruction.
The Department of Forestry Bulletin is available to
readers free of charge by contacting the corresponding
author of this manuscript.
11
14
12
13
Musella
Gwinnett
Hiwassee
Davidson
15
19
Designing parabolic waterways
Michael T. Aide*
Tallapoosa
16
Grover
17
Rion
18
Pacolet
Wedowee
Cataula
20
Madison
Abstract
Parabolic waterways are man-made structures designed to
transport water nonerosively. These waterways are especially
popular where siltation may be a problem. Previously a trialand-error approach has been employed to determine the dimensions. Described in this manuscript are computer-generated solutions that are used more easily in student-generated field plans.
21
Cecil
Appling
Louisburg
Wateree
individuals were able to correlate soils themselves rather
than relying on the authors to visit study sites. The taxonomic key approach should help alleviate the reluctance
of foresters, vegetation ecologists, and botanists to include soils when studying the interrelationships of vegetation and environment (R.D. Pfister, Univ. of Montana
School of Forestry, Missoula, MT, 1988, personal communication).
The keys were published in a field guide format in June
of 1987 as a Clemson Univesity Department of Forestry
G
RASS WATERWAYS are designed to transport water
nonerosively and with a minimum of silt deposition. Parabolic cross sections are especially popular when
surface drainage from depressional areas is desired (Fig.
1). Advantages of the parabolic cross section include the
transport of small flowages without silt deposition, which
is probable with trapezoidal cross sections. The velocity
is more nearly constant at all flow volumes with the
parabolic cross section, because the width changes more
Department of Agriculture, College of Science and Technology,
Southeast Missouri State Univ., Cape Girardeau, MO 63701. Contribution from Dep. of Agric., Southeast Missouri State Univ. Received 23
Oct. 1987. 'Corresponding author.
Published in J. Agron. Educ. 17:129-130 (1988).
J. Agron. Educ., Vol. 17, no. 2, 1988
129
tions (Eq. [1] and [2]), each involving only the terms t
and d; thus, a solution is possible.
2t = 18.1m
i
d = 0.19m
'(t,d)
(0,0)
Area = 2.29m 2
Fig. 1. Parabolic cross-section illustrating sample depth and width
measurements and resulting area.
than the depth; therefore, better velocity control may be
obtained but at the expense of a more complex design.
To design a parabolic waterway, the designer needs
estimates of the peak flow (Q), the maximum permissible velocity (V), slope (S), and the coefficient of
roughness (n). Estimates of the coefficient of roughness
and recommended flow velocities based on soil texture
and vegetation are given in van Schilfgaarde (1974, p.
118). Beasley (1980) provides an excellent description of
a trial-and-error approximation for determining the
dimensions of a parabolic waterway given the above
information.
Beasley (1980) demonstrates how to use field data (V,
n, S) to calculate a value for the hydraulic radius (R) using Manning's formula (V = l.49R2/3S1/2/n). By definition, the hydraulic radius is equivalent to the crosssectional area (A) divided by the wetted perimeter (WP).
Since R and A are obtainable, a value for the wetted
perimeter is calculable.
Program Design
Consider the basic shape of a parabolic waterway
where d is the maximum depth and 2t is the width. The
cross-sectional area may be calculated as Q/V. If an equation relating d and t to the cross-sectional area can be
derived, then t is a function of d. The algebraic descrip-
tion of a parabola may be written as y = (d/t2)x2 where
the parabolic vertex is at the origin and d/t2 is defined
by requiring the parabola to pass through the point (t,d).
By integrating under this curve and subtracting the result
from the rectangular area 2td, we obtain an estimate of
the area in terms of t and d:
Q/V = A = (4/3)dt
[1]
It may be shown by integrating from 0 to t using the
distance integral for arc length (Thomas, 1969) that the
wetted perimeter may be expressed in terms of t and d:
WP = B + (t2/2d) In \(2d + B)/t I
where B = (4d2 + r)1
130
[2]
. Clearly there exist two equa-
J. Agron. Educ., Vol. 17, .no. 2, 1988
Example
A parabolic waterway must be constructed to carry a
peak water flow (Q) of 2.80 m3 s~' down a 5% sodcovered slope. A maximum permissible velocity (V) of
1.22 m s ~' and a coefficient of roughness (n) of 0.068
were selected because of the soil's texture and excellent
grass sod (Beasley, 1980). The cross-sectional area (A)
is 2.29 m2 (calculated from Q/V) and the hydraulic
radius determined by Manning's formula is 0.124 m. The
wetted perimeter (WP) is calculated as the cross-sectional
area divided by the hydraulic radius and is equal to 18.4
m.
A value for depth (d) is found by iteration. If a value
of 0.01 m is substituted for d in Eq. [1], then a solution
for t can be obtained. Now with values for d and t, the
right side of Eq. [2] can be computed. If the value of the
right side of the Eq. [2] is greater than WP, then increment d by 0.001 m and repeat the iteration. Continue the
iteration process until there is agreement between WP and
the right side of Eq. [2]. In this example the depth is 0.18
m and the width (2t) is 19.1 m.
Classroom Usage
The undergraduate soil conservation course at
Southeast Missouri State University provides instruction
in the design of waterways and terrace systems. Computer
software, written by the author, substitutes for the extensive graphs and iterations formerly required to
calculate cross-section dimensions. This approach allows
students without a broad base in mathematics and
graphics to design farm conservation plans.
A listing of the computer programs for calculating
trapezoidal and parabolic waterways can be obtained
from the author. In addition, the author will supply
detailed calculations involved in generating Eq. [1] and
[2], or the reader may consult Chow (1959). Send requests
to M.T. Aide, Department of Agriculture, College of
Science and Technology, Southeast Missouri State
University, Cape Girardeau, MO 63701.
Changing careers: From
teacher to researcher
D. A. Knauft*
Abstract
Through
a 10-yrperiod,the authornoticeda perceptibledrop
in his motivation
for teaching.Contributing
factorsfor this loss
of motivation
includeda desire for moreobjectivepeerrecognition, a needfor moreobjective self evaluation,burnout,the
needfor greaterflexibility in the demand
for his time, anda
desire for morevarietyin the processof the job. Thisloss of
motivationcould be addressedif teachingresponsibilities,
especiallyat land-grant
institutions, werespreadmoreequitably
amongthe faculty. Teachingwouldneedto havemorepositive
reinforcement
for this to be successful. Theindividual with
heavyteachingresponsibilitiescouldlessen motivation
problems
by increasingthe varietyof activities requiredin the position.
Thiscouldincludeteachingseveraldifferentcoursesratherthan
severalsessions of the samecourse,or takinga breakfromthe
teachingcycle throughsabbatical leaves or alternate summer
programs.
was taught twice each year; a graduate-level genetics
course; an undergraduate plant breeding course; and a
graduate microcomputer/statistics course. At times, I
taught classes in crop production or oilseed crops. Additional responsibilities included academiccounseling, student club advising, and graduate student committee and
advisory work. Mylimited research activities involved
peanut breeding and genetics.
The Changeto a Research Position
Through the years I had noticed a gradual reduction
in my motivation for teaching. Recently I had the opportunity to switch from teaching to research when the
peanut (Arachis hypogaea L.) breeding program leader
at the University of Florida announced his retirement.
Initially I did not consider this potential changeof position as a solution to mymotivational problem, because
I thought I did not want to leave teaching. However,after
a great deal of reflection, I opted to accept this appointment that involved virtually no teaching.
The change to a research position was a rather drastic
one that, upon contemplation during the past year, I
realize I made for a number of reasons.
Lack of Enthusiasm. A contributing factor was the difficulty I experienced in generating enthusiasmfrom either
myself or mystudents. After teaching meiosis and mitosis
FTER10 WARSin a position that was primarily
for the twenty-first time, I found myself tired of explainteaching (80070teaching/20070research), I found
ing the topic and impatient whenstudents did not underincreasingly difficult to motivate myself to teach with the
stand it immediately. This was a striking change for somesame interest and enthusiasm I possessed earlier in my
one whoformerly could spend hours patiently describcareer. This loss of enthusiasm came about for many
ing the phenomenonto students.
reasons, but primarily because I felt caught in a cycle that
Desire for Peer Recognition of My Accomplishments.
rarely seemed to change. I continued to teach the same
I had put in the long hours required for competencein
classes over and over again.
teaching, and, as shownin their teacher evaluations, the
On the other hand, I viewed research as an opportunistudents appreciated it. Myteaching expertise was supty to makeprogress in a linear fashion. After successful
ported by the administration of the University of Florida,
completion of an experiment, I could build on the inforas evidenced when I received tenure and promotion. My
mation generated and learn more about the subject area,
colleagues in the department were supportive, although
rather than conducting the same experiment again. This
at times I wondered if part of the support was merely
desire for a different type of professional growth caused
gratitude
that I was teaching in their place. Yet I saw my
me to make a career shift from teacher to researcher.
colleagues developing national and international reputaAlthough I trained for 4 yr in graduate school for a
tions in their fields of expertise through their hard work
career in agricultural research, I taught for the first time
and quality research, while my hard work and quality
during mylast semester as a graduate student. This exteaching
gave me a reputation only amongmystudents.
perience was so positive that, upon completion of my
I realized that teaching excellence is something that is
Ph.D. in plant breeding and genetics, I accepted a posialmost impossible to demonstrate to colleagues at a nation as a teacher. I enjoyed the challenge of sharing my
tional level. On the other hand, myresearch peers can
knowledgewith students, making genetics exciting, and
be somewhat objective in judging research quality
unraveling the mysteries and confusion of this subject
through the evidence of cultivar release and publication
area. For the first 10 yr of myprofessional career, my
record.
job included teaching an average of five courses a year
This dichotomy began to bother me. Anyone could
to an annual total of about 300 to 350 students. These
pick up a journal and read research articles, whichwould"
courses included the introductory genetics course, which
point out the expertise of mycolleagues. However,unless
Departmentof Agronomy,304 NewellHall, Univ. of Florida,
one of my peers met a former student who had apGainesville,FL32611.Contribution
fromthe FloridaAgric.Exp.Stn.
preciated myteaching and was interested in discussing
JournalSeriesArticleno. 8628.Received
28Dec.1987.*Corresponding it, my teaching expertise never was knownoutside the
author.
classroom. The primary method for evaluating quality
of teaching is the course evaluation. The results of course
Publishedin J. Agron.Educ.17:131-133
(1988).
A
J. Agron. Educ., Vol. 17, no. 2, 1988 131
evaluations are usually not disseminated the same way
research articles are disseminated. Unlike research, where
virtually any scientist can pick up one of mypublications
and read of mywork, teaching requires essentially a personal contact for others to establish somesort of opinion
about the job I did.
I also realized that the subjective nature of peer evaluation of the teaching process was not only preventing
others from evaluating me, but it was also a less than
satisfactory wayfor self evaluation. AlthoughI could see
and measure the research I was conducting, I had contact with only a few students after they left the university and could only assume they had benefitted from my
teaching.
Burnout Syndrome. Although faculty can face this
problem in any academic position, those with heavy
teaching loads generally find it to be more acute. I felt
constant, low-level stress from the pressure of presenting
a polished "performance" for each class, of facilitating
and participating in a quality laboratory experience twice
a week, and constantly preparing handouts and exams
before a given deadline. Although the change from
teaching to research did not reduce the number of hours
I worked, it offered the opportunity for a less structured
demandon my time and talents. While research must be
conducted in a timely fashion, most of the experiments
! carry out do not require the same combination of constant newpreparation delivered at such a precise time each
day.
Lack of Variety. I also felt there was an opportunity
in research for the process I used in myprofessional life
to be more varied. While teaching allows some latitude
in methodsof instruction, the constraints of budget, time,
and class size limited the number of new procedures I
could use. However, in research on peanut genetics, I
could study the inheritance of physiological traits,
biochemical composition, yield, and morphological
characteristics, each involving different research techniques for the measurementof the characteristics being
studied.
Repetition. Perhaps the most compelling reason for my
switch to research was the feeling that myjob was becoming repetitive; I kept teaching the same classes over and
over again. I saw mycolleagues branching out into new
research areas, while I was still teaching the same subjects in the same classroom with only slight variations as
! incorporated new research results and new teaching
techniques. AlthoughI tried to lessen this repetition by
teaching five different courses beyond mymain responsibilities of genetics and plant breeding, I still becametired
of teaching epistasis over and over again and re-explaining
the single seed descent method. I saw researchers in my
department involved in a numberof different experiments
that, once finished, would generate information leading
to additional, different experiments. In contrast, once I
finished teaching a course, I wouldstart to teach it over
again.
Although I became frustrated with these issues, I had
not planned to leave teaching. However, when the op132 J. Agron.Educ., Vol. 17, no. 2, 1988
portunity to expand the research I was already conducting was presented, I chose that opportunity. Had my
research associate not retired, I would have stayed in
teaching, faced with the concerns I have mentioned. During the time I was teaching, I tried to deal with the frustration I was facing and I have continued to think about
the problem, leading to several suggestions that mayhave
either prevented, or at least lessened, mydissatisfaction
with teaching.
Teachers and Researchers Working Together
The problems of lack of personal motivation, burnout,
and frustration with job repetition partially could be
alleviated by providing teaching positions with more
variety. In land-grant institutions, faculty whogenerally
do only research could occasionally teach one or two
courses for a person with a heavy teaching load in exchange for research assistance from the instructor.
Perhaps the best solution at these universities would be
to have faculty teach no more than three or, at the most,
four courses a year.
For institutions with research programs, this would
mean no faculty member would have a large teaching
commitment, and all faculty would have some teaching
appointment.
The concern that such a switch would produce a
plethora of poorly taught courses because research faculty
are not interested in teaching is a real one. The major
way this concern could be addressed is for university administration to place the same emphasis on quality
teaching as is placed on quality research. Beyondthis,
research faculty should be made aware of the positive
aspects of teaching. I am more competent as a researcher because of my teaching experience. Teaching courses
in genetics, plant breeding, oilseed crops, crop production, and microcomputers and experimental design has
given me a much more thorough background in a wide
range of subject areas crucial for myresearch than my
graduate program ever did.
Interpersonal Relationships. Other benefits that could
be stressed to a researcher reluctant to move into the
classroom would include improved skills in interpersonal
relationships, somethingthat rarely, if ever, is taught in
graduate agronomyprograms. Teaching also provides the
opportunity
for contact with larger numbers of
undergraduates interested in graduate school, giving the
faculty member and the student opportunity for a
graduate research program "prescreening."
Another
benefit could be improved writing skills as a result of
creating handouts and exams, as well as grading papers
and projects.
Variety. Another method to help deal with the problems associated with job repetition is interruption of the
teaching cycle. Taking a break, especially during the summer term, can be a useful way to reduce the heavy concentration on teaching whether one is at a teaching and
research institution or at a teaching college. The time
could be used for research or consulting. Taking advan-
tage of faculty developmentleaves or sabbaticals to update knowledgein chosen subject areas can be beneficial
for improving both motivation and quality of instruction.
Variety can also be generated by teaching different
courses. Myteacher "burnout" might have occurred even
sooner had I not made the decision to teach an average
of one new course a year. Probably the major contributor
to my loss of motivation and burnout was teaching the
same course twice a year. Different faculty members
should be involved in teaching classes that must be offered
more than once a year.
Research. Research itself can be an important source
of variety for someonein a teaching position. In addition to the variety, research can enhance one’s teaching
capabilities by providing personal experiences that can
be drawn on to explain or demonstrate important concepts. The research, of course, also allows one to develop
peer recognition. Unfortunately, most teaching faculty
find it difficult to generate the external funds necessary
for an adequate research program. Lack of time to
prepare grant proposals and a more meager "track
record," both due to teaching commitments, are important contributors to this problem. Administrators need
to realize this funding problem for teachers and utilize
institutional research support accordingly.
Conclusion
Unfortunately, overcoming the lack of peer recognition for teaching will be extremely difficult. I knowof
no objective way to evaluate teaching, and without the
generation of some type of teaching counterpart to
research publications, national peer recognition for instructors will most likely not take place.
Perhaps there are alternative ways to improve peer
recognition of the teaching activity itself, even if the individual instructors are not recognized. Most researchers
realize that their work has little value if no one knows
the results of their research. Publishing research findings
makes them valuable by passing the information
generated by the research to others whoalso mayuse it.
As such, publication is an important component of the
research process. The scientific communityshould realize
that teaching is also communicationof research findings,
but on a different scale. Faculty membersteaching in their
area of expertise communicate not only their own
research findings and research ideas, but the findings and
ideas of others. The form of communicationis oral rather
than written, and the audience is composedof graduate
and undergraduate students rather than other researchers.
Weneed to convince researchers and administrators that
both types of communication are important.
I imagine manyin the teaching profession have shared
some of the same frustrations I felt. Mypersonal solution, simply changing to a research job, is not always
available to faculty membersand should not be regarded
as the best alternative. Most faculty teach because of a
genuine interest in the profession and should be encouraged to remain in teaching.
A simple laboratory exercise
to improve data presentation
and interpretation skills
S. J. Corak and L. J. Grabau*
Abstract
Beginningstudents in crop science often lack both an
understanding
of the scientific method
andthe ability to present andinterpret experimental
data. Asimpleandinexpensive
laboratoryexercise wasdevisedto addressthese needs, which
wereclarified as the followingbehavioral
objectives:(i) employ
the scientific method
in person,and(ii) improve
skills in data
presentationandanalysis. As a class, we tested the effect of
the number
of holes in a containerlid on the number
of seed
that wouldfall fromthe containerduringa single, rapidtip.
Studentswereaskedto predicta probableoutcome
beforebeginning the experiment.Dataobtainedby each groupof students
wereplotted on the board.Somedeviations fromanticipated
results wereobserved.However,
a plot of meanvaluescalculated
by poolingdatafromall groupsgenerallyconformed
to expectation. This helpedto illustrate the conceptof replication.
Overall student response to this laboratory session was
favorable. Weaccomplishedour primaryobjectives andwere
also able to stimulateclassroom
participationduringthis first
laboratorysession.
W
E HAVE
OBSERVED
that manystudents in our introductory agronomy course, "Principles of Field
Crop Production," had difficulties presenting and interpreting experimental data. A lack of understanding of
the scientific methodwas also prevalent, as evidenced by
student’s commentsand failure to comprehend this important method. Specific deficiencies included the inability to construct a line graph, transpose data onto the
graph, and draw meaningful conclusions from data
presented.
These deficiencies amongour students should not be
all that surprising, since we, as professionals, have often
been guilty of statistical misuses (10). It maybe that
students are simply reflecting our own inadequacies as
instructors. This failure to correctly understand and interpret statistical information carries with it a numberof
dangers. For example, students may be led to erroneous
conclusions about a given research result by their instructors’ incorrect interpretation of the data (5). It is thus
incumbent on us to be careful in our own presentation
of research results and to train our students to read
reports critically (5).
Bothauthors, Dep.of Agronomy,
Univ.of Kentucky,Lexington,KY
40546-0091.
Contribution
fromthe Univ.of Kentucky
Agric.Exp.Stn.
Received18 Feb. 1988.*Corresponding
author.
Publishedin J. Agron.Educ.17:133-135
(1988).
J. Agron.Educ., Vol. 17, no. 2, 1988 133
Methods available to improve student understanding
of scientific methods(6), and the presentation and interpretation of results derived through its use, include field
experiences (3) and the use of demonstration trials (12).
The utility of field experiences is obvious; however,this
training is available to only a limited portion of our
students due to scheduling and work conflicts. Swearingen and Holt (12) reported the use of "blank" small
grain variety trials, with statistical analyses conductedas
if the plots had been planted to several varieties; in reality, only one variety was used at each location. This
method provided a memorable experience for the area
crops extension agents involved and led to better
understandingof key intuitive and related statistical concepts. However,a serious limitation exists for classroom
use. Its presentation is necessarily abstract, does not involve students actively, and runs a high risk of communicationfailure with those students not adapted to less
active teaching methods (9).
Laboratory experiments can provide "hands-on" involvementfor all students without the limitations of field
studies or blank variety trials. In the past, laboratory experiments published in this journal have included new
devices to illustrate someconcepts of herbicide leaching
(1), soil pedoturbation (2), splash erosion (7), or
growing plant systems to teach crop growth analysis (4).
This last report is of particular interest here, since the
authors also incorporated the use of the statistical
parameters of mean, standard deviation, and standard
error. While this experiment has been subsequently incorporated into our crop production laboratory, we felt
a strong need to establish a commonground in the use
of the scientific methodearlier in the semester than its
analysis wouldallow. The simple exercise described below
provides a basic frameworkwithin the first laboratory
session, thus saving the teaching assistant a good deal of
time in grading other experimental write-ups submitted
prior to the conclusion of the crop growth analysis
experiment.
Based on the above discussion, an informal, interactive information session was developed to be followed by
a simple, quick, and inexpensive laboratory exercise. Our
specific behavioral objectives (8, 11, 13) were to have
students (i) employthe scientific methodin the laboratory
exercise, and (ii) improve skills in data presentation and
analysis.
Materials and Methods
Preliminary Discussion Session
Thepreliminarydiscussion session was conductedto introduce
and define the concepts of the scientific method.Pursuit of
knowledgeand problemsolving were presented as the goals of
scientific research. It was demonstratedthat science-related
problemscould be divided into those requiring either deductive or inductive reasoningfor solution. Thescientific method
wasoutlined and the use of the experimentas an objective tool
for hypothesistesting wasdiscussed. Theconceptsof treatment
and treatmenteffect werepresented,althougha detailed discussion of statistical methodswas avoided. Students were asked
134 J. Agron.Educ., Vol. 17, no. 2, 1988
Table1. Students’results of the number
of seed that fell from
the containers
havingzeroto five holesperlid duringa single,
rapidtip.
Studentgroup
Numberof
B
holes
A
C
D
E
Mean
0
0
0
0
0
0
0
1
2
3
3
4
2
2.8
3
12
9
12
1,5
11
11.8
13
14
15
14.8
5
18
14
for examplesof experimentsfrom their ownfields of study.
Transition to the laboratory exercise was accomplishedby
reviewingthe four steps of the scientific method:development
of an hypothesisto be tested, objective experimentation,data
acquisition,andanalysis of results (6). Anoutlineof the discussion section follows below.
Discussion Overview:
I. Self-introduction of teaching assistant
II. Goalsof scientific research
A. Pursuit of knowledge
B. Problem solving
1. Deductive reasoning
2. Inductive reasoning
a. Hypothesis development
b, Objective experimentation
c. Data acquisition
d. Analysisand interpretation of results
Laboratory Exercise
Thefollowingmaterials wereused by each groupof students:
1. Four 500-mL
ice creamcontainers with either zero, one,
three, or five I cmdiamholes per lid. Holeswerecut using
a cork-borer set to 1.0 cmdiam.
2. Enoughsoybean[Glycinemax(L.) Merr.] seed to fill each
container to approximately70%of its capacity.
3. Container to catch seed.
It is worthyof note that all requiredmaterials werecollected
from the homeor laboratory, and therefore no teaching funds
wereused to implementthis exercise.
Students wereaskedto volunteera hypothesisfor the effect
of the numberof holes in the lid uponthe numberof seed that
wouldfall from the container during a single, rapid tip.
Eachcontainer was completelyoverturned, from the vertical
upright position to the vertical downward
position, for approximately0.5 s before beingreturnedto the vertical upright position. Each group of students performedthe tip one time for
each of the four treatments. The numberof soybeanseed falling into the catching container was counted for each tip.
Data from the entire class were recorded on a chalkboard
(Table1). At this point the line graphwasintroducedalongwith
a brief discussionof independentand dependent
variables, labeling of the graph, and the mechanicsof using a line graph. Data
from each group were then plotted on separate graphs drawn
on a chalkboard. The experimentwas conductedby both sections of the laboratory portion of this crop productioncourse
in one semester.
Results and Discussion
The hypothesis
most commonly volunteered
by
students was that more seed wouldfall from the container
as the number of holes was increased. Specific numeric
predictions were not made, but in retrospect, would have
been desirable. Some deviations from the students' expectations were observed. However, a plot of mean values
calculated by pooling data from all groups generally conformed to the students' original hypothesis. This effectively demonstrated the importance of replication in scientific experiments.
This experiment reinforced those concepts of the scientific method that had been presented in the preliminary
discussion session, particularly the need for objective experimentation and careful data acquisition. It also served
to introduce and/or review the function and mechanics
of line graphing in an effective and acceptable manner.
Conclusions drawn directly from the graph enabled
students to practice inductive reasoning skills. Additionally, linear interpolation was presented using the plot of
means as an example. A value for the number of seed
falling from two holes in the lid was predicted from the
graph. Students were able to test this prediction.
This laboratory session was used during the first
meeting of the semester. The format employed helped to
establish an informal and participatory environment
within the classroom. Together with the preliminary
discussion, the experiment appeared to achieve our intended objectives. Since a control group was not included,
our conclusions on the effectiveness of this experiment
are based primarily on observation. Errors in data presentation and interpretation were less frequent than in the
preceeding semester, and an improved understanding of
the scientific method was apparent.
Measuring the chemistry
expertise of an incoming class
in introductory soil science:
A guide to course preparation
Paul B. Francis*
Abstract
Lack of familiarity with basic chemistry may diminish a student's ability to grasp certain topics in introductory soils courses.
A pretest designed to evaluate the knowledge of basic chemistry
as related to applications in soil science was given unannounced
on the first day of class and repeated during the final examination of an introductory soil science class at the University of
Arkansas at Monticello. Areas tested were molecular and
equivalent weight calculations, cations and anions, acidity/basicity, simple tit ration, and percentage calculations. Pretest
results indicated severe weaknesses in equivalent weight determination and simple titration. A lecture and assignments were
given to students in an attempt to strengthen the weaknesses
prior to topics requiring knowledge of these chemical concepts.
Posttest results indicated that more effort was needed in teaching
the applications of equivalent weight in soil science.
I
NTRODUCTORY SOIL SCIENCE is a required course for
several agriculture degree programs in universities
throughout the USA. For many nonplant and/or soil
science majors, introductory soil science can be a very
difficult course because of the volume and complexity of
the material covered.
Personal observations from introductory soil science
courses taught at five universities have indicated that student comprehension is lowest for those topics requiring
a basic knowledge of chemistry. This lack of understanding is apparent from both lower test scores and student
complaints. Topics in introductory soil science requiring
a basic understanding of chemistry include cation/anion
exchange, liming, nutrient availability, colloids, fertilizers, denitrification, and microbial decomposition of
organic matter.
A freshman-level chemistry prerequisite for introductory soil science is standard for most universities. Unfortunately, many agricultural students do not take introductory soil science until their junior or senior years. This
can be sufficient time for students to lose considerable
skills in basic chemistry.
Greene (1931) found that students lose approximately
50% of detailed facts within the first 4 months after completing courses in college-level zoology, psychology, and
Agriculture Dep., Univ. of Arkansas, P.O. Box 3508, Monticello, AR
71655. Received 28 Mar. 1988. 'Corresponding author.
Published in J. Agron. Educ. 17:135-137 (1988).
J. Agron. Educ., Vol. 17, no. 2, 1988 135
chemistry. An80 to 90°7o loss occurred at the end of 20
months. Overcoming a deficiency in chemistry is
necessary in order for a student to comprehendthe areas
of introductory soil science previously mentioned.
To deal with the students’ lack of knowledge in
chemistry, the introductory soil science instructor must
determine the chemistry comprehensionlevel of the class
as it relates to soil science. Then appropriate action can
be taken to correct the deficiency.
One tool to measure the background of an incoming
class is a pretest. Elkins (1987) used a pretest to identify
the entry level knowledgeand background of students in
an introductory crops course at Southern Illinois University. The information obtained was helpful in modifying
course content and stimulating student involvement.
The chemistry backgroundas it relates to soil science
was evaluated in the introductory soil science class at the
University of Arkansas, Monticello’s fall semester in
1987. The objectives of the project were to
1. Determine the knowledge of basic chemistry as it
relates to soil science for an incomingclass
2. Use this information to modify the course, if
needed, to provide a more meaningful and challenging learning experience
3. Determine at the completion of the course if the
learning experience helped basic chemistry
comprehension.
Table 1. Pretest questions.
No.
Questions
1. Place a "C" by the ions that are cations and an "A" by those that are
anions.
2+
+
Ca
Nor
ClNa
~ +
AI 3SO,~Mg
K+
2. Write the molecular weight and the equivalent weight of the following
compounds:
Co__~_pound
Mol. wt. (a)
Atomic wt.
E~ wt. (b)
CaCO3
C-12
KCI
O-16
HNOa
H-1
MgIOH)2
Mg-24
HCI
C1-35
Ca-40
N-14
K-39
3. Supposeyou titrate a 10-mLsolution of 1.0 MHCiwith a solution of
NaOHof an unknownmolarity. Exactly 20 mL of NaOHare used to
reach the reaction endpoint. Whatis the molarity of the NaOH7
4. Suppose you have 200 kg of fertilizer
that is 30% N. Howmanykg
of actual N do you have? Howmanykg of another fertilizer that is
only 10% N is needed to get the same amount of N?
5. Consider the following solutions. Whichone is more acid?
Solution
~._
A
4.4
B
5.0
C
4.3
6. Definesoil.
Table 2. Average scores to pretest questionsff
Question no.
Precourse score
Methods
A simple pretest was designed to determine the chemistry
backgroundof an incomingintroductory soil science class. The
test wassimple, short, and designedto measurethe students’
comprehension
of chemistryin five general areas used mostfrequently in soil science, whichare
1. Cations and anions
2. Molecular and equivalent weights
3. Simpletitration, pH
4. Percentage mathematics
5. Acids/bases
Thetest (Table1) wasgivenonthe first dayof class andagain
duringthe final examination.In bothinstancesthe test wasgiven
unannounced. Pre- and postcourse results were compared
statistically by analysisof varianceprocedures(SASInst., 1982).
Thetest results fromthe first class periodwereusedas a guide
for modifications of course content and outside class
assignments.The results fromthe last test gave insight as to
whether or not the course changes improved the students’
knowledgeof chemistry.
Results
Precourse
Scores from the first test revealed severe deficiencies
in the determination of equivalent weights and simple
titration (Table 2). It was also evident that somedeficiencies were present in calculations with percentages.
An understanding of equivalent and milliequivalent
weight is extremely important for topics such as cation/
136
J. Agron.Educ., Vol. 17, no. 2, 1988
Postcourse score
%
1
2a
2b
3
4
5
75.0
71.7
10.0
25.0
62.5
88.3
91.7"
83.9 NS
14.3 NS
50.0 NS
46.4 NS
92.9 NS
* Significant at the 0.05 level of probability. NS= not significant.
~ Refer to Table 1 for question content.
anion exchange, liming, and soil testing. To respond to
this deficiency, outside class assignments and a 30-rain
lecture during a laboratory period were used in an attempt
to help students gain the needed chemistry background.
This was done approximately 2 wk before the lectures on
cation exchange and liming. It was also hoped that this
would challenge the students and mentally prepare them
for what lay ahead. Students were advised to review their
chemistry notes dealing with titrations and percentage
mathematics,
although
no mandatory hand-on
assignments were given.
Postcourse
The postcourse results were not very encouraging, particulady in the area of equivalent weights (Table 2). More
effort was needed to assist students in their comprehension of equivalent and milliequivalent weights. No improvements were noticed in percentage calculations or
titration.
Mandatory hand-on assignments may improve
these deficiencies if noticed in the future. The students'
scores showed a significant improvement on their ability
to distinguish cations and anions. Advising students to
take introductory soil science as soon as possible after
completing freshman chemistry might help them perform
better in the soil science course.