Soil Science Society of America Journal 65:1-3 (2001)
© 2001 Soil Science Society of America
HISTORY OF SOIL SCIENCE
Who Invented the Tensiometer?
Dani Or
Department of Plants, Soils and Biometeorology, Utah State University, Logan, UT 84322-4820
Corresponding author (dani{at}mendel.usu.edu)
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ABSTRACT
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The invention of the tensiometer for measurement of soil water matric potential is commonly attributed to Willard Gardner, with the first robust design for field applications attributed to Lorenzo A. Richards during the early 1920s. However, evidence shows that the original design was proposed by Burton E. Livingston as early as 1908 (perhaps earlier) with advanced implementation of similar concepts for "measuring the capillary lift of soils" by Lynde and Dupre in 1913.
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INTRODUCTION
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ONE OF THE MOST USEFUL DEVICES for monitoring soil water status is the tensiometer. It consists of a porous cup (usually made of ceramic with very fine pores) connected to a vacuum gauge (mechanical or electronic transducer) through a rigid water-filled tube (Fig. 1)
. The porous cup is placed in intimate contact with the bulk soil at the depth of measurement. When the matric potential of the soil is lower (more negative) than the equivalent pressure inside the tensiometer cup, water moves from the tensiometer along a potential energy gradient to the soil through the saturated porous cup, thereby creating suction sensed by the gauge. Water flow into the soil continues until equilibrium is reached and the suction inside the tensiometer equals the soil matric potential (i.e., when the driving force dissipates). When the soil is wetted, flow may occur in the reverse direction; that is, soil water enters the tensiometer until a new equilibrium is attained.
In their textbook Soil Physics, Marshall et al. (1996) attributed the introduction of the tensiometer to Richards (1928)(whose original drawing is shown in Fig. 2a)
. Cassel and Klute (1986) attributed the first complete description of the tensiometer to an abstract published by Gardner et al. (1922). The description in Gardner's abstract reads:The apparatus used consists of a porous cup closed with a water-tight joint and connected through a tall tube to an exhaust pump. The cup is surrounded by a thin layer of soil in the outer vessel and atmospheric pressure is maintained on the soil side. The pressure is then reduced on the water side and measured, and by means of a glass tube the amount of water in the soil is determined.
While it has been accepted for quite some time that Willard Gardner (Utah Agricultural Experiment Station, Logan, UT) invented the tensiometer, Haines (1927) showed a design of a modern tensiometer (Fig. 2b) attributed to Livingston (1918). Inspection of work published by Livingston (1908)(1918) and Livingston and Hawkins (1915) convincingly shows that the tensiometer was invented more than a decade before the description by Gardner et al. (1922).
Thus, the earliest account of a tensiometer or a tensiometer-like device was reported by Livingston (1908). The method proposed by Livingston (1908)(1918) uses all the elements of a modern tensiometer to automatically control soil water status of potted plants (Fig. 3a)
. A liquid-filled porous cup was brought into contact with the soil. The measurement capability of a similar device was demonstrated by Pulling and Livingston (1915) who used an osmometer with a collodion osmotic membrane backed by sugar cane solution (as depicted in Fig. 3b) to measure the "water supplying power of the soil."
A related early development was reported by Lynde and Dupre (1913) who described experimental methods for "measuring the capillary lift of soils." The basic design is that of a hanging water column as shown in Fig. 4
(note that the experimental setup was capable of measuring capillary pressures in soils for ambient pressures different—greater or lower—than atmospheric).
In summary, Livingston (1908) appears to be the first to have implemented a tensiometer for measurement and control of soil matric potential. The most likely precursor for this invention was the so-called porous cup atmometer (Livingston and Hawkins, 1915, p. 11). These authors cited work by Babinet (1848), who named the device atmidoscope. The analogy and the process were explained by Livingston and Hawkins (1915): "In the porous cup atmometer evaporation removes water from the system. In the auto-irrigator the `capillary' attraction of the surrounding soil brings about the same result. As water passes from the cup to soil it automatically distributes itself so as to tend towards equilibrium throughout the soil mass."
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ACKNOWLEDGMENTS
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The manuscript benefitted from stimulating discussions with Wilford Gardner, Art Warrick, Jon Wraith, Markus Tuller, Scott Jones, and Teamrat Ghezzehei, and from constructive review comments by R.D. Miller and an anonymous reviewer. The partial support of the Utah Agricultural Experimental Station and the Western Regional Project W-188 are gratefully acknowledged. Approved as UAES journal paper no. 7336.
Received for publication April 3, 2000.
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REFERENCES
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- Babinet, J. 1848. Note sur un atmidoscope. Compt. Rend. 27:529–530.
- Cassel, D.K., and A. Klute. 1986. Water potential: Tensiometry. p. 563–596. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed.Agron. Monogr. 9 ASA, and SSSA, Madison, WI.
- Gardner, W., O.W. Israelsen, N.E. Edlefsen, and D. Clyde. 1922. The capillary potential function and its relation to irrigation practice.(Abstract) Phys. Rev. 20:196.
- Haines, W.B. 1927. Studies in the physical properties of soils: IV. A further contribution on the theory of capillary phenomena in soil. J. Agric. Res.(Cambridge) 17:264–290.
- Livingston, B.E. 1908. A method for controlling plant moisture. Plant World 11:39–40.
- Livingston, B.E. 1918. Porous clay cones for the auto-irrigation of potted plants. Plant World 21:202–208.
- Livingston, B.E., and L.A. Hawkins. 1915. The water relation between plant and soil. p. 3–48.Publ. 204. Carnegie Inst., Washington, DC.
- Lynde, C.J., and H.A. Dupre. 1913. On a new method of measuring the capillary lift of soils. J. Am. Soc. Agron. 5:107–116.
- Marshall, T.J., J.W. Holmes, and C.W. Rose. 1996. Soil Physics. Cambridge Univ. Press, Melbourne, Australia.
- Pulling, H.E., and B.E. Livingston. 1915. The water supplying power of the soil as indicated by osmometers. p. 49–84.Publ. 204. Carnegie Inst., Washington, DC.
- Richards, L.A. 1928. The usefulness of capillary potential to soil moisture and plant investigators. J. Agric. Res.(Cambridge) 37:719–742.
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