Reprinted from SOIL SCIENCE SOCIETY OF AMERICA PROCEEDINGS
Vol. 25, No. 4, July-August 1961
Pages 321-325
Tension Lysimeter Studies of Ion and Moisture Movement
In Glacial Till and Coral Atoll Soils'
41043
D. W. Core, S. P. GesseL anp E. E. HEtp?
ABSTRACT
The alundum tension lysimeter originally described was
modified to allow installation in shallow soils and to
facilitate collection of the leachate. The lysimeter plates
were located at various depths in two contrasting soil
types to study the ion content of the gravitational water.
In addition, the influence of potassium (added as KCl)
and nitrogen (added as (NH,)2SO,) on ion movementin
the soil was studied.
The ion content of the gravitational water changed
markedly with soil type, depth, month of the year, and
daily weather conditions. KCl and (NH,).SO, soil additions distinctly altered established soil dynamics, increasing movement of other soil elements including the
radionuclide cesium!" from local fallout in 1954 on
Rongelap Atoll soils.
oxe THE EARLY sTuDIES of De LaHire (4) in 1708,
and Ebermayer (7) in 1897, lysimeters have been
widely used in agriculture and forestry research to obtain
information on the nature, amount, and movement of
gravitational water. In general, they have been commonly
employed to studysoil development (12); fertilizer losses
(1, 5); and evapotranspiration (8, 10).
The validity of information derived from lysimeters has
been repeatedly questioned (8, 11, 15), primarily on the
grounds that the soil-air interface at the outlet retards
normal soil drainage. Drainage occurs only when the
soil immediately above the outlet is saturated; thus, the
volume of water flowing from the lysimeter may be less
than that which would normally drain from the soil. Most
lysimeter types also impose definite restrictions on roct
development by the very existence of vertical side walls.
These sources of error are particularly significant in
studies of ion and water movement through forest soils.
Here the investigator is dealing with a community. of
plants, both annuals and perennials, which have widely
developed interrelated root systems.
Thus, to study the influence of various environmental
factors on the passage of ions and water through a forest
soil, a special type of lysimeter was developed, representing a modification of the tension lysimeter previously
reported by the author (2). In orderto test the field usefulness of this lysimeter as well as obtain data on movement of water and ions under two widely contrasting
environments, the lysimeters were installed in coral atoll
soils of the northern Marshall Islands and a glacial till
soil of western Washington. The ion content of the gravitational water was studied in relationship to soil type, soil
depth, season of the year, daily weather conditions and
fertilizer application. The data presented in this article
are intended to illustrate the influence of the above factors
‘This project was sponsored in part by the National Science
Foundation and the Laboratory of Radiation Biology at the
University of Washington under contract number AT (45-1)
540 of the Atomic Energy Commission, Division of Biology
and Medicine. Presented before Div. V-A, Soil Science Society
of Amcrica, Cincinnati, Ohio, Nov. 17, 1959. Received June
21, 1960. Approved Feb. 24, 1961.
“Research Associate in Forestry, Associate Professor in Forest
Soils, and Research Assistant Professor in Radiation Biology,
respectively.
on the movement and loss of both water and ions in several widely differing soil profiles.
EXPERIMENTAL PROCEDURE
The Lysimeter
The lysimeter developed by the senior author (2) minimizes
the soil-air interface problem. A negative tension (suction)
is placed against the soil through an alundum filter plate. Thus,
the capillary force of the soil at field capacity is opposed by
the negative tension exerted against the alundum plate. Whenever soil tension is decreased by an increase in soil moisture
content, from rain or irrigation, water is removed from the
soil until it returns to field capacity. Since the tension against
the plate is maintained at a constant value, it is possible an
undue amount of water is extracted during the early phases
of the drainage cycle. This error would be greatest in heavy
soils during intense rain or rapid irrigation. In well-drained
soils used in this study, this error was not noticed.
.
As originally conceived, the tension system was established
and maintained by gravity through a water column. The
necessary excavation posed practical problems in soils containing hardpan or bedrock; and in other situations, limited the
depth at which a lysimeter could be established.
The tension lysimeter as redesigned requires a hole only
deep cnough to locate the plate. All equipment except the
plate is above the ground, simplifying the collection of
leachates and servicing of equipment. The components, illustrated in figure 1, are: (@) vacuum tank, to maintain the
system over an extended period; (b) Cartesian manostat, to
maintain the desired magnitude of vacuum from the tank
to the rest of the system;
(c)
distribution tank, to allow
a series of plates to be controlled by a single vacuum tank; (d)
collection carboy, to receive leachates passing from the
lysimeter plates; and lysimeter plate to intercept gravitational
water as it passes through the soil. The lysimeter plate is
constructed from an ll-inch fused alundum dise as described
by Tanner (13) for a tension table and Cole (2) for the
original tension lysimeter. All tubing is 3/16-inch ID tygon.
The vacuum tank (figure 2) is constructed from 16-gauge
stainless steel reinforced inside with channel iron. A vacuum
gauge (i) on the side of the tank indicates the vacuum
reserve. Air is removed from the tank through the toggle valve
Figure 1—Alundum tension lysimeter with the tension
maintained and controlled through a vacuum system:
(a) vacuum tank for maintaining the system over a
period of time; (b) Cartesian manostat for controlling
the vacuum from the tank to the rest of the system;
(ec) distribution tank to allow a series of plates installed
from one vacuum tank; (d) collection carboy, 5 gallons;
(e) hole excavated for installation of plate.