https://en.wikipedia.org/wiki/Long-term_experiment
A long-term experiment is an experimental procedure that runs through a long period of time, in order to test a hypothesis or observe a phenomenon that takes place at an extremely slow rate.
Several agricultural field experiments have run for more than 100 years, but much shorter experiments may qualify as "long-term" in other disciplines. An experiment is "a set of actions and observations", implying that one or more treatments (fertilizer, subsidized school lunches, etc.) is imposed on the system under study. Long-term experiments therefore contrast with nonexperimental long-term studies in which manipulation of the system studied is impossible (Jupiter's Great Red Spot) or undesirable (field observations of chimpanzee behavior).
A long-term experiment is an experimental procedure that runs through a long period of time, in order to test a hypothesis or observe a phenomenon that takes place at an extremely slow rate.
Several agricultural field experiments have run for more than 100 years, but much shorter experiments may qualify as "long-term" in other disciplines. An experiment is "a set of actions and observations", implying that one or more treatments (fertilizer, subsidized school lunches, etc.) is imposed on the system under study. Long-term experiments therefore contrast with nonexperimental long-term studies in which manipulation of the system studied is impossible (Jupiter's Great Red Spot) or undesirable (field observations of chimpanzee behavior).
Physics
The Oxford Electric Bell has been ringing at Oxford University since 1840, although there is some reason to believe it may be 15 years older. The Beverly Clock at the University of Otago has been running since 1864.
The pitch drop experiment has been running at the University of Queensland since 1927.
Botany
The William James Beal Germination Experiment has been running since 1879. It is the oldest on-going experiment in botany. It is scheduled for completion in 2100.
The Godwin Plots experiment at the Wicken Fen reserve in Cambridgeshire,
England, has been running since the 1920s and explores the differences
between areas of vegetation which are never cut, and respectively all
four, three or two years and every year.
Long-term agricultural field experiments
Broadbalk Experiment Rothamsted
Long-term experiments test the sustainability of different farming
practices, as measured by yield trends over decades. Examples include
the Park Grass Experiment at Rothamsted Experimental Station (1843–present), the Morrow Plots (1876–present) at the University of Illinois at Urbana–Champaign, the Magruder Plots (1892–present) at Oklahoma State University, Auburn's Old Rotation (1896–present), and the Haughley Experiment (1939–1982?).
Experiments at Rothamsted showed that "grain yields can be
sustained (and even increased) for almost 150 years in monocultures of
wheat and barley given organic or inorganic fertilizer annually". These results show that practices considered unsustainable by some advocates of sustainable agriculture may preserve "the ability of a farm to produce perpetually", at least under some circumstances. But even if crop diversity in space or time (crop rotation)
and organic inputs are not always essential to sustainability, there is
abundant evidence from Rothamsted and elsewhere that they are often
beneficial.
An experiment in alpine pasture has been ongoing in Switzerland at Schynige Platte from the 1920s looking at the human effect on the alpine environment.
The Haughley Experiment was noteworthy as a rare example of a
long-term experiment in organic farming without external inputs of
nutrients. After about 30 years, however, it was decided to start
importing manure. There is some disagreement whether a "decline in
relative yields from the organic section" was due to a depletion of soil
nutrients.
Various short-term experiments have used legumes (in symbiosis with nitrogen-fixing rhizobia)
as a nitrogen source, but good short-term yields do not prove the
system is sustainable. The problem is that release of nitrogen from soil organic matter
can make up any shortfall of nitrogen from legumes for a decade or
more. The Old Rotation showed that nitrogen from legumes can balance
nitrogen removed in a harvested crop over the long term. A key point is
that the nitrogen in the legumes was not removed, as it would be with a
soybean crop, but was plowed under as a green manure. In the Old
Rotation, the green manure was grown during the winter to supply
nitrogen to a summer crop (cotton); this would be less practical in
colder climates.
Long-term agricultural experiments that have been started more recently include the Long-Term Research on Agricultural Systems experiments at UC Davis, started in 1993.
Long-term microbiology experiments
A photo showing the components of the 500-year microbiology experiment
Chroococcidiopsis glass ampoules
At the UK Centre for Astrobiology within The University of Edinburgh and at the Institute of Aerospace Medicine with the German Aerospace Centre, Charles Cockell and Ralf Möller established the "500-Year Microbiology Experiment" that started in July 2014 to study the loss of viability of desiccation-resistant
bacteria over long periods. The experiment involves the study of
vegetative bacteria (the extreme tolerant cyanobacterium, Chroococcidiopsis sp.) and spore-forming bacteria (Bacillus subtilis).
The experiment comprises two oak wooden boxes containing duplicate samples, to be kept at the University of Edinburgh and the Natural History Museum.
Every two years for the next 24 years, triplicate samples of both
organisms contained within glass ampoules will be opened and the number
of viable cells enumerated. The first time point was taken in 2014.
Within each box, the experiment is duplicated into a reduced and
non-reduced background radiation experiment, with one set of samples
being kept in a lead box to cut back background radiation, allowing the
impact of radiation in combination with desiccation on viability to be
studied over long periods. It was motivated by a desire to understand
how microbes survive desiccation in deserts, rocks, permafrost and their
potential survival in space. The destruction and pathways of
degradation of biomolecules will also be studied. In addition to the
core experiment, there are a variety of samples including dried agar
plates and endoliths for investigation over long periods.
One of the wooden boxes was delivered to the Natural History
Museum on 27 February 2015, and will be curated within the
cyanobacterial collection.
In evolutionary biology
The experiments of Richard Lenski on evolution of E. coli have been underway since 1988 for more than 50,000 generations.
Experiments with the evolution of maize under artificial selection for
oil and protein content represent more years, but far fewer generations
(only 65).
The domesticated silver fox, an ongoing breeding program since 1959 with dramatic results.
Long-term ecological experiments
The
US National Science Foundation supports a number of long-term
ecological experiments, mostly in ecosystems that are less directly
affected by humans than most agricultural ecosystems are. See LTER. Within the UK the Ecological Continuity Trust
works to promote and secure the future of long-term ecological
experiments, maintaining a register of experiments where treatments have
been applied for a minimum of six years.
A number of other areas, sometimes called involuntary parks, can be regarded as long time ecological experiments, because they have been abandoned by humans and returned to near-feral condition. These include areas abandoned for political reasons, such as the Korean Demilitarized Zone, or environmental contamination, such as the Chernobyl Nuclear Power Plant Exclusion Zone.
Medicine and psychology
The Framingham Heart Study has been running continuously since 1948.
The Grant Study at the Laboratory of Adult Development in the Department of Psychiatry at Brigham and Women's Hospital, a Harvard Medical School affiliate, is conducting a longitudinal study of human adult development, by following two groups of individuals as they age (268 Harvard graduates and 456 males from inner-city Boston). The study has been ongoing since 1937 and is currently the longest running study of adult life ever conducted.
