Novel way in teaching introductory soil science.
Wadia, Adil M. ; Clark, William B.
ABSTRACT. The importance of soils is often underemphasized in
introductory undergraduate geology courses, despite their relevance to
students and the communities in which they live. The high agricultural
productivity of United States and the economic well-being of many of its
communities are dependent on the physical properties of soils, as well
as agricultural practices, human and natural history, and climate.
Although this could be realized through lectures and memorization, in
order to achieve the metacognitive changes necessary to promote
long-term understanding and behavioral change associated with resource
planning and conservation, learning activities that promotea deep
approach rather than a surface approach to learning must be utilized. In
this way students are engaged in activities in which they are actively
searching for meaning, rather than engaging in rote memorization. This
paper discusses a teaching method in which the learning objectives,
activities, and assessment are aligned to achieve this aim and presents
evidence of its efficacy over seven years of its use.
Date of Publication: 11 November 2015
INTRODUCTION
Soils can be defined in a variety of ways depending upon the area
of interest. For instance, a geologist may consider soils as products of
weathered rocks. An engineer may place greater emphasis on the physical
properties of soils--namely texture, structure, drainage, and strength.
A pedologist may define soils as a natural body, comprised of
unconsolidated rock fragments and organic matter in various layers, and
approach soils as an object to study and understand without any
particular bias. An agronomist would define soils as the unconsolidated
cover of earth, composed of mineral and organic components required for
plant growth (Kohnke and Franzmeier 1995).
Soils are important for various reasons. Besides obvious value in
agriculture, soils play an important role in affecting the nature of a
host of other human activities, including environmental resource
planning and conservation; waste disposal; recreational purposes such as
parks, golf courses, and camp grounds; and foundations on which to
construct (Wadia 2004).
The importance of soils in introductory geology courses is not
often emphasized. Typically, soils receive a cursory mention in
textbooks, which cover a very small portion in chapters that include
sedimentary rocks and weathering processes. At most, these chapters
mention soil profiles and factors responsible for their formation, which
include climate, vegetation, topographic relief, parent material, and
time (Jenny 1941). The relationship among soil forming factors is a
complex interaction best summed by the equation, Soil = f(p, cl, r,
[phi]) t, where p = parent material, cl = climate, r = relief, [phi] =
organic material, and t = time (Buol and others 2011). Nevertheless,
memorization of these factors or of this equation is not likely to serve
introductory or non-major undergraduate geology students well. Instead,
such students need to be presented with an engaging exercise that will
allow them to discover these relationships in a context that is
meaningful to them.
Students enrolled in The University of Akron Wayne College, in
Orrville, Ohio, are predominantly first-generation students who live
within 25 miles of the rural campus situated on what was, until its
foundation in 1972, a working farm. In fact, many fixtures from that
time still remain, including a farmhouse and derelict antique farming
equipment. To this date, portions of this campus on which campus
buildings have not been erected are leased to area farmers.
The state soil for the State of Ohio is the Miamian silty clay
loam, which covers more than 750,000 acres. These soils are fertile
supporting main crops such as winter wheat, soybeans, and corn according
to United States Natural Resource Conservation Service (USNRCS), United
States Department of Agriculture (USDA), Ohio (Accessed 2015). Table 1
summarizes the characteristics the soil profile of typical Miamian soils
found in Ohio. (USNRCS, USDA, Ohio. Accessed, 2015).
Agriculture is a major part of the economy in Wayne County, Ohio,
within which the highest percentage of land usage is devoted to cropland
and pasture (Table 2) (United States Department of Agriculture National
Agricultural Statistics Service (USDA-NASS), 2007).
Wayne County, Ohio, ranks highest in the state among 88 counties in
the following categories: milk-dairy product from cows; fruits, tree
nuts, and berries; other crops and hay; corn for silage; forage land
used for all-grass sileage, greenchop, and hay and haylage; and cattle
and calves, as well as third-highest in the state for total value of
livestock; poultry; and for the total value of agricultural products
sold.
PREVIOUS WORK
Instructors of introductory geology courses are often challenged by
the competing need to introduce an experiential component into their
courses and constraints imposed by the dangers and logistical challenges
of introducing inexperienced students into areas containing geologically
interesting features such as stream banks and outcrops (Hudak, 2003).
Hudak (2003) has demonstrated that utilizing campus features as data
collection models of processes such as weathering and retaining wall
stability can be effective substitutes of more inspiring settings. As
Hannula (2003) has shown, as long as a lab compels students to state a
hypothesis, conduct observations, and make data-based inferences
concerning the validity of the initial hypothesis, then students will
have gained experiential knowledge in the scientific method; even
mundane settings such as those utilized by Hudak (2003) are useful in
this regard.
Knapp et al. (2006) have implemented engaging experiential lab
experiences in an institution with the advantage of local access to the
Appalachian Fold. However successful, the model utilized in this
instance does not generalize well to inexperienced first-semester, first
generation students, as it relies heavily on Geographic Information
Systems (GIS) and statistical analysis. Clearly, this program is
successful, but does it does not generalize to other students and
settings without considerable adjustment.
Given the relative inexperience of The University of Akron Wayne
College students with the scientific method and the local agricultural
riches, it seems that the locale presents a relatively safe, natural
laboratory of local exploration. Learning experiences emphasizing the
importance of soil are relevant, not only because the proximity of farms
both on and adjacent to campus allows students to take field trips in
order to study soil texture, structure, composition, and organic matter,
but because these factors matter to the local economy in which they
live. Student engagement is enhanced, not only because soils are located
near the classroom, but because it is so clear that soils matter to the
country's economic strength and local livelihood.
Because of this relevance, these exercises represent optimal
alignment of learning objectives, activities, and context, as described
by Biggs (1999a). Given that predominance of agriculture in the local
economy, relatively few of parents of students are college educated and
have modeled the expected approach to problem solving in higher
learning. It is important to select teaching methods that will encourage
students to engage learning activities with an academic orientation that
first generation students would be less likely to spontaneously (Biggs,
1999b). Requiring students to actively seek answers to questions
discourages them from taking a passive surface approach to learning
(such as memorizing and note-taking), and instead compels students to
take what Marton and Saljo (1976) term as a deep approach (such as
applying and theorizing). Accordingly, requiring students to apply and
theorize concerning how soils play a critical role in the maintenance of
their local economy and livelihood represents optimal alignment of
curriculum in undergraduate teaching of geology.
MATERIALS AND METHODS
As part of the "Ice Age and Ohio" spring course offering
at The University of Akron Wayne College, from 2008 to 2014, students
completed a learning activity designed to actively engage them in
learning, so as to encourage them to discover the importance of soils as
a natural resource. Initially, students are engaged in a discussion
concerning the major glacial periods affecting Ohio and their role in
shaping the land, flora, and fauna observed today. Students learn that
the soil that predominates locally is classified as a Miamian silty clay
loam, and that a soil of this texture has much to do with both
Ohio's glacial past and the present agricultural riches of Wayne
County.
Silty clay loam soils formed from loess are ideal for agriculture
because they hold nutrients, moisture, and humus better than sandy soils
(Buol and others 2011). However, it is a combination of natural history,
human history, and current practice that maintains superior
productivity. Rather than simply presenting students with a list of
these factors, students are asked to discover these through inductive
reasoning, by way of answering a series of three questions, presented in
six parts (Wadia 2011).
Through this learning activity, students attempt to answer the
following questions, and arrive at the following conclusions, as
learning activities and objectives, respectively:
1) Why is the agricultural productivity of soils in the United
States generally better than other parts of the world (aside from the
technological advances, quality of fertilizers, pesticides, etc.)
considering:
1a) the duration of agricultural activities in the United States:
Objective (conclusion): The duration of farming in the United
States (approximately two centuries) is considerably less than in parts
of Asia and Africa, where agricultural activities span a few millennia.
Therefore, the soils in the United States are much younger, fresher, and
more fertile, as they have been farmed for a relatively shorter
duration.
1b) the effect of the United States' winters:
Objective (conclusion): The growing season in the United States in
many places (mainly the Midwest) is restricted from about April-May to
September-October. For the rest of the year, the soils are frozen, and
winters give soils a break. Furthermore, snow provides a protective
covering reducing soil decomposition.
1c) the historic effects of glaciation in North America:
Objective (conclusion): The Pleistocene Age (Ice Age) resulted in
glaciers bringing fresh new material, which influenced the fertility of
the soil, as well as the topography.
2) Why are crops rotated from season to season?
Objective (conclusion): Different crops take up as well as return
different nutrients to the soil, and keep the soil at its optimum. A
crop may be farmed for two consecutive years, but after that, a
different crop should be planted. For instance, needed application of
nitrogen is reduced when corn is planted after soybean, as compared with
that required between two consecutive corn growing seasons (Schoessow
and others 2010; Crops and Soils 2011).
3) After crops have been harvested, why are the stalks kept in
place?
Objective (conclusion), (two part answer):
Part 1: As the stalks decay, they return nutrients back into the
soil.
Part 2: The stalks are kept in place after harvest in order to
reduce soil erosion, as stalks act as soil binding-tethering mechanisms.
Students were asked to prepare written answers to each of these
questions outside of class. However, they were free to discuss their
answers among themselves and to use whatever resources they wished, so
long as they provided appropriate citations of their sources. At the
conclusion of the written exercise, student responses were discussed in
class; weather permitting, a field trip was also conducted to one of the
farms close to campus, so as to reinforce the concepts that were covered
in the exercise.
RESULTS
Student responses were evaluated by the instructor for accuracy and
thoroughness, according to the following rubric: two points per each of
the three parts of question one (soil productivity), two points for
question two (crop rotation), and one point per each of the two parts of
question three (leaving stalks in place). Accordingly, the greatest
weight was given to responses concerning soil productivity. The merit of
each of the six scored responses was evaluated separately from the other
five. However, no fractional points were awarded, and one point was not
awarded as partial credit either for question two, or any part of
question one.
The aggregate sum of points awarded for each semester was produced,
and this was divided by the number of participating students to yield a
mean term score. Conveniently, the maximum number of points awarded per
student is 10, so the resulting term score can be intuitively
interpreted without further transformation. Generally, the desired
benchmark for a given class is that students be able to answer these
questions sufficiently so as to earn 75 percent of the total points
possible. As can be seen in Figure 1, this was achieved five out of the
seven semesters. In addition, at the level of the individual student,
across all semesters, it can be inferred from Table 3 that more than 75
percent of the time, of all students achieve a score of eight or better.
Overall, the exercise produces the added value to student learning that
is expected.
Furthermore, individual comments made by student participants
suggest that the exercise has the desired effect of increasing student
engagement. First, some students remark that questions concerning the
relative agricultural productivity of the United States versus other
parts of the world are particularly challenging. Second, many commented
that their internet searches for quick answers were not of much help.
Finally, some students resorted to consulting individuals involved with
farming. These latter instances, in which students were compelled to
actively seek information in their community, represent ideal outcomes.
At the least, there is compelling evidence that these exercises are
prompting some students to approach problems with an academic
orientation to a greater extent than they would if not for the personal
and local relevance of these activities.
DISCUSSION
Soils play an important role in a number of human activities; for
most University of Wayne College students, agriculture, resource
planning, and conservation will be paramount. However, resource planning
and implementation of conservation measures, in particular, are
long-term endeavors that require multigenerational commitment. Although
students can be compelled to memorize a list of soil forming factors,
this would do little toward developing appreciation of how these factors
affect their livelihood and compelling students to consider these in
their future decision making. This is because, as Biggs (2003) states,
students typically second-guess coming assessment tasks and learn what
they believe will meet the requirements; thus, memorization tasks will
likely evoke a surface approach to learning at odds with the development
of metacognitive skills necessary to practice conservation. This is
increasingly problematic with students who are not prone to approaching
problems with an academic orientation, and as class sizes grow larger
(Biggs 2003).
[FIGURE 1 OMITTED]
Proper alignment between not only the learning objectives and
learning activities, but also assessment practices, dissuades a surface
approach to learning, encourages an academic approach, and promotes the
development of lifelong learning (Biggs 1999b). In this exercise,
students cannot simply memorize the correct answers; instead, they must
seek them out through sources that they must identify, and must persist
in their search until they themselves are satisfied with the answer.
Further, the instructor's evaluation of the work product is not a
statement of right or wrong, but of the quality of the response in terms
of sufficiency of the explanation, merit of the writing, and the breadth
of the resources used. Not only do students receive a score, they
receive feedback, both individually and as groups. As individuals,
students receive constructive feedback, as appropriate. As a group,
particularly commendable efforts are discussed, in order to recognize
them and to model superior work and effort. In this manner, assessment
of students' work product is what Ainsworth and Viegut (2006) term
as formative rather than summative. As such, the evaluative criteria
reinforce the initial educational objective of learning about the impact
of soils, and ultimately applying this learning.
ACKNOWLEDGMENTS
The authors would like to thank Lisa Nagy, Coordinator of Library
Services at The University of Akron Wayne College for assistance in
obtaining some of the journal articles used in this research.
LITERATURE CITED
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ADIL M. WADIA (1), Department of Geosciences, and WILLIAM B. CLARK,
Office of Academic Affairs, University of Akron Wayne College, Orrville,
OH, USA
(1) Address correspondence to Adil M. Wadia, Department of
Geosciences, The University of Akron Wayne College, 1901 Smucker Road,
Orville, OH 44667. E-mail: amwadia@ uakron.edu
TABLE 1
Soil Profile of the Miamian Soils
Encountered in the State of Ohio
Soil Horizon Depth Characteristics
A 5-10" Very dark grayish brown
to brown silt loam or
loam as topsoil
B 8-35" Brown or yellowish
brown subsoil layer
C >35" Brown or light olive
brown substratum;
slightly or moderately
alkaline and has a lower
clay content than B
TABLE 2
Percentage Distribution of Land By Activity
in Wayne County, Ohio (USDA-NASS, 2007)
Activity Percentage
Cropland 77.66
Pasture 8.98
Woodland 8.31
Other Uses 5.04
TABLE 3
Summary of Results (scores and numbers of
students earning that score over 2008-2014)
Individual Frequency Cumulative Cumulative
Student Frequency Percent (%)
Scores
10 47 47 33.8
9 36 83 59.7
8 22 105 75.5
7 15 120 86.3
6 8 128 92.1
5 5 133 95.7
4 4 137 98.6
3 1 138 99.3
2 1 139 100.0
1 0 139 100.0
0 0 139 100.0
Total 139 139 100.0
