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News from ICTP 104 - Features - Soil Physics
The ICTP College on Soil Physics celebrated its 20th anniversary this year. The activity has proved a valuable source of training for hundreds of scientists worldwide.
Soil Physics:
Twenty Years On
In 1980, while attending the
ICTP Autumn Course on the Physics of Flow in the Oceans, Atmosphere
and Deserts, Donald Gabriels casually sat down for lunch in the
Centre's Main Building cafeteria. As he turned to his side, he
was surprised to see the Centre's director, Abdus Salam, sitting
next to him.
"Our conversation was what you would expect-seemingly nothing
more than casual cafeteria chatter," Gabriels, a professor
of agricultural engineering, University of Ghent, Belgium, recently
recalled. "Salam asked me which activity I was participating
in and what was my major field of research."
"Soil physics, I told him."
"You should prepare a course outline on the subject, Salam
quickly replied, and send it to me. Perhaps we can organise a
workshop here."
"Delighted by his invitation, several weeks after returning
to my university, I sent Salam a detailed course outline and a
brief description of the workshop's objectives. He responded in
short order, saying the Centre had tentatively scheduled to hold
a training activity on the subject. It was one of the most extraordinary
turns of events in my career."
And, as Gabriels would subsequently learn, an unusual example
of the sometimes positive power of miscommunication. You see,
at their lunchtime encounter, Salam thought that Gabriels had
said his major field of interest was solar--not soil--physics.
"Salam was expecting a course outline dealing with subjects
close to the Centre's core fields of study in theoretical physics-perhaps
an exploration of issues related to subatomical behaviour dealing
with sunspots, solar magnetism and hydrogen bounding. What he
received, instead, was a course outline with such headings as
soil erosion, compaction and siltation."
"But rather than dismissing what I had given him, Salam was
intrigued enough to let the proposal move forward. Only several
years later, after our biennial colleges on soil physics had become
a regular feature on the ICTP calendar, did Salam let me know
that the activity was based on a mutual misunderstanding of what
we had talked about at lunch."
The chance encounter--and misunderstanding--between Salam and
Gabriels, which took place more than two decades ago, unwittingly
laid the groundwork for one of ICTP's most unusual activities:
the College on Soil Physics. Over time, some 500 scientists--80
percent of whom are from developing countries--have participated
in the programme, which this March celebrated its 20th anniversary.
What is soil physics? In the simplest terms, it is the study of
the physical characteristics of soil. Put another way, which emphasizes
the dynamic processes that drive soil formation, use and evolution
(and not just the medium itself in a static state), soil physics
is the study of the physical laws of nature governing the behaviour
of soil.
"While the definition of soil physics may appear simple,"
adds long-time College organiser Edward Skidmore, "the reality
is that soil physics is a subject of infinite complexity. The
study--and, equally important, the potential applications--of
soil physics involve an understanding not only of physics but
of biology, chemistry, hydrology, engineering and even land-use
management." Skidmore, a research leader at the US Department
of Agriculture, Agricultural Research Service, Manhattan, Kansas,
has also served as one of the principal architects of the activity
since its inception.
Edward Skidmore, Donald Gabriels, GianCarlo Ghirardi,
Ildefonso Pla Sentis and Donald Nielsen
The reason soil physics is so complicated lies in the fact that
the health and behaviour of the soil depends on a complex interplay
of factors: the physical and chemical composition of the soil;
the diversity of flora and fauna living within the ecosystem in
which a particular type of soil is present; the number and variety
of soil microbes; the altitude and slope of the landmass; the
rate and intensity of rainfall; and the density of human population
and patterns of land development.
"Those who study soil physics," adds Donald Nielsen,
a former dean at the University of California, Davis, USA, and
the third 'founding' organiser of the event, "must process
large amounts of data and information in order to build models
that help us understand and, at times, anticipate soil behaviour
under ever-evolving conditions--some of which are induced by nature,
others by human activities.'' In developing such models, soil
physicists must continually excavate a complex academic terrain
that resides at the unspecified boundaries of mathematics, physics,
chemistry, biology and agricultural science.
But, as Nielsen is quick to add, ''soil physics is not just an
academic exercise. It carries important implications for understanding
and responding to some of the most critical issues of our time:
food security, access to safe drinking water, air and water pollution,
and the prospects for such natural disasters as flooding and landslides."
To shed light on these critical phenomena, soil physicists need
to examine such complex environmental forces as erosion, water
flow, runoff, soil transport, and carbon and oxygen diffusion.
The wide ranging critical issues that draw on information and
insights provided by soil physics were on full display at this
year's College, which took place from 3 to 21 March. Researchers
came from a variety of fields that included not only physics but
agricultural science, biology, chemistry, engineering, forestry
and land-use management. Their places of work ranged from academic
research centres to governmental agencies to universities to burgeoning
private-sector consulting firms. Fifty-five out of 57 participants
came from developing countries or countries with economies in
transition.
The participants' scholarly research and on-the-ground work-related
projects ranged from the construction of an irrigation system
in the drought-prone Indian province of Guwahati; to the study
of soil composition in Ghana, where food shortages remain a threat
to public health and the physical well-being of the citizens;
to the development of soil-related instruments in Brazil that
help to measure the soil's water-retention capabilities, which
is a critical parameter in determining the soil's potential health
and long-term viability for food production.
The personal commitment and enthusiasm that participants at the
College had for their work was clearly conveyed in how they chose
to describe what they did.
"Don't call it dirt. It's not dirty. In fact, it's one of
cleanest, most pristine materials that you would ever want to
handle," says Daniel Okae-Anti, an agricultural scientist
at the University of Cape Coast in Ghana, who was attending the
College for the third time.
Okae-Anti's good natured but heartfelt description reflects his
deeply rooted personal commitment to the study of soil genesis,
which involves analysing the parent materials--the rock, sand,
water, chemicals and microbes--that interact with one another
under ever-changing climatic and weather conditions to create
a particular category of soil. Okae-Anti notes that scientists
have identified more than 200 orders or classes of soil worldwide
and that each one of these orders may be divided into subcategories
based on virtually endless local and regional ecological factors
and processes.
Other participants at the College, including Gautam Barua, a professor
of civil engineering at the Indian Institute of Technology, in
Guwahati, India, and Carlos Vaz, an agricultural researcher at
EMBRAPA's (Empresa Brasileira de Pesquisa Agropecuaria)
Agricultural Instrumentation Institute, in São Paulo, Brazil,
share Okae-Anti's sense of commitment to the study of soil. All
agree that what they do represents more than a job to them.
"My work in India will help continue my country's efforts
to increase the nation's food supply," says Barua. "We
now recognise that increasing the level of food production in
the short term cannot take place at the expense of the long-term
health of the soil, which could suffer from rising levels of salinisation
if our irrigation systems deplete groundwater levels faster than
they can be replenished. The models that I helped to devise have
enabled us to create engineering blueprints that serve both our
short- and long-term needs for healthy and productive soil."
"The tensiometers that I designed," notes Vaz, "have
allowed field workers to record valuable information on the level
of water in the soil and the ability of the soil to retain water
during periods of low rainfall. Such data is critical for determining
the soil's potential productivity as well as its responsiveness
to crop-rotation or irrigation strategies that might be implemented.
In a sense, agriculture throughout much of the world has become
an information-intensive industry and what I do helps increase
the level of scientific data that both farmers and agricultural
policy makers need to succeed."
"Just like beauty," Barua adds, "details are in
the eyes of the beholder. And our ability to better understand
the intricate nature of soil--in all of its elegant complexity--holds
the key to addressing some of the world's most critical concerns."
"Some people may call it dirt, but on closer inspection,
the soil is indeed one of nature's most elegant media and, more
importantly, the basis of one of earth's most fundamental life-giving
elements: our food supply."
For the past two decades, the ICTP College on Soil Physics has
helped train hundreds of scientists to better apply their skills
and talents to such a vital concern. This year--the 20th anniversary
of the College--offered an opportunity for participants to extend
their thanks to those who have made the activity possible, most
notably directors Donald Gabriels, Edward Skidmore, Donald Nielsen
and, more recently, Ildefonso Pla Sentis, coordinator of Escuela
Latinoamericana de Fisica de Suelos (ELAFIS), as well as GianCarlo
Ghirardi, professor of theoretical physics at the University of
Trieste and long-time ICTP consultant, who has been the College's
local organiser since the beginning.
If the enthusiasm displayed by the participants of this most recent
College is any indication of things to come, the 20th year anniversary
will likely be followed by many more Colleges in the years ahead.