Gardner, W R
Wilford Robert Gardner 1925 (Logan, Utah, USA) - 2011 (Mapleton, Utah, USA)
Wilford Gardner was born October 19, 1925 to Robert and Nellie Barker Gardner in Logan, Utah. He was a veteran of World War ll and served with the Army Corps of Engineers in the European and Pacific Theatres of Operation. He married Marjorie Louise Cole on June 9, 1949 in the Logan Temple. Wilford earned his Bachelor of Science from Utah State University in 1949, during which time he also performed as a flutist in several musical ensembles including a woodwind quintet.
His pathway to soil physics was all but inevitable, given that much of the foundational work in the field had been done by members of his own family. the study of physical processes in unsaturated soils did not really begin until early in the 20th century with the arrival of Wilford’s uncle Willard gardner at the Utah State Agricultural College (now Utah State University) in logan in 1917. Willard had received the eighth PhD. ever granted in physics by the University of California at Berkeley, and over the next 30 years he elevated the field of soil physics from a small area within agricultural science to a legitimate branch of physics. Wilford’s father, Robert, became a soil chemist and taught soil physics for a time at Colorado State University. Willard’s son, Walter, had a long career in soil physics at Washington State university, earning a reputation as a skilled scientist and one of the finest teachers in the field. Thus, almost inevitably, both Wilford and his brother Herb entered the field of soil physics as well.
He went on to complete a Master of Science degree in soils physics and a Ph.D. in soil physics and mathematics at Iowa State University, where he worked under Professor Don Kirkham, the foremost soil physicist of the day. The two of them worked together to develop the use of neutron scattering as a method for measuring the quantity of water held in soil. This device was to become the principal means for quantifying water storage in soil for the next three decades. After completion of his doctorate he accepted a research position at the U.S. Salinity Laboratory in Riverside, California where he worked closely with L.A. Richards. Subsequently he received a professorship at the University of Wisconsin where he taught from 1966 through 1980.
During this time he served as a Senior Fulbright Fellow and in 1972 was awarded the Medal of Honor by the University of Ghent, Belgium. In 1980 he accepted a position at the University of Arizona as head of the Department of Soil and Water Science. From 1987 and 1994, he served as Dean of the College of Natural Resources at the University of California, Berkeley. During his tenure at Berkeley he also served as Bishop of the Richmond 1st Ward.
Over the course of his career, he published over 140 books, chapters, and scholarly articles. He served as an active member of many associations devoted to soil science. He was a fellow of the Soil Science Society of America, the American Society of Agronomy, and the American Association for the Advancement of Science. He received the Soil Science research award, the top honor of that society, was a Centennial Alumnus from Utah State university, received the Berkeley Citation from UCB, an honorary doctorate from Ohio State University, and an honorary professorship from the Chinese Academy of Sciences. He was also a member of the Water Science and Technology Board of the National Research Council. He was the first USU graduate to be elected to membership in the National Academy of Sciences in 1983. He was the president of the physics committee for the International Soil Science Society, head of the delegation to International Union of Soil Science, chair of the United States National Committee for Soil Science, and served as president of the Soil Science Society of America.
Wilford Gardner was a major contributor to soil physics and the understanding of evaporation and transpiration from the soil-vegetation-atmosphere interface. , and in the modelling of water uptake by roots.
At the time Wilford arrived in riverside, scien- tific understanding of water retention and flow in soil was in its infancy. equations for water transport had been formulated, largely through the efforts of Willard gardner, but they were highly nonlinear and therefore unsolvable by any methods available before the advent of high-speed computers. moreover, the equations contained transport coefficients that were nonlinear functions of water content, and methods had not been developed to measure their values in soil. This field was ready to be plowed by the new wave of scientists trained in physics and mathematics.
Soon after Wilford started at the Salinity lab he began analyzing data on the water-saturated permeability of soils. He discovered that the varia- tion of this value within a soil-mapping unit was much better described by a lognormal distribution than the commonly used normal distribution. further study showed him that soil particle size distribution was also better described as lognormal than normal. this observation, which he published, was the first indication that soil property variability deviated greatly from the assumed normal distribution upon which most sampling statistics were based.
Wilford’s initial major contribution to soil physics research was to make the first measurement of the unsaturated hydraulic conductivity (then called the capillary conductivity) as a function of the energy state of water. Water in unsaturated soil is adsorbed to the surface of soil minerals, which causes the air-water inter- face within soil pores to curve inward toward the liquid, thereby lowering the pressure of the water held in soil pores relative to free water. l. A. Richards had designed and built a pressure membrane apparatus to measure the equilibrium relation between the water content in soil and its energy state. using this device called for placing a wetted soil sample held in a ring on a water-saturated ceramic plate within a sealed chamber connected to the outside through a tube attached to the plate. When the air pressure in the chamber was raised, the water was expelled from the soil through the membrane and out the chamber, leaving the remaining water at an energy state opposing the applied air pressure. the applied air pressure. Wilford enhanced this method by measuring the rate at which the water left the chamber and interpreting this rate through a linearized form of the flow equation, which allowed him to measure the coefficient of permeability (the hydraulic conductivity) as a function of both the energy state of the water and the water content of the soil. His published paper reported measurements of￼hydraulic conductivity over six orders of magnitude, something that had never been accomplished before.
He made important contributions in the approximate analytical solution of the Darcy-Buckingham-Richards equation for various boundary conditions. One of his approximations was to assume that the transport coefficients were exponential functions of the water content or of the energy state of the water (expressed as a soil water potential). this functional relationship, which was a reasonable approximation over a practical range of water content for many soils, allowed him to transform the flow equation into a linearized form and create solutions to a variety of hitherto unsolvable problems. in his classic paper of 1958 he used this method to calculate the maximum possible evaporation of water from a water table as a function of the depth of the water table below the soil. He also demonstrated that coarse-textured sandy soils conduct far less water upward to the surface than their finer-textured counterparts, even though sandy soils are much more permeable than finer-textured ones when both are saturated.
Later, working with Carl Ehlig, Wilford was able thoroughly to characterize the factors limiting plant growth under conditions of both adequate and inadequate water supply. In a classic paper in Science he and Ehlig demonstrated that the limiting resistance to water flow from the soil to the plant shifted from that produced by plant tissue and membranes under wet conditions to the soil permeability under dry conditions. in a second paper in Science, Wilford and Neimann demonstrated through measurements of plant transpiration, cell division, and cell enlargement that no single lower limit of available water could be defined for these three plant processes. The soil-water content at which permanent wilting is exhibited does not represent a true lower limit for any of these. this paper largely dispelled the previous belief that plant-available water is a measurable soil characteristic.
Wilford also continued his work on plant-water relations while at Wisconsin. His student Mary Beth Kirkham conducted a number of studies examining the effect of soil salinity on plant water stress, cell growth, and cell division. they simultaneously monitored turgor pressure and stomatal conductance, developing a number of relationships between soil conditions and plant response. Wilford had previously studied plant roots’ resis- tance to water uptake arising from soil and plant condi- tions, and with his student Frank Dalton he examined in detail the simultaneous movement of water and solutes across plant membranes. He and dalton published a theory describing the hydraulic and osmotic transport of water and the diffuse, convective, and active transport of solutes across root membranes. the theory predicted a nonlinear relationship between the flux of water and the pressure difference across root membranes, which was in good qualitative agreement with a variety of observa- tions on simultaneous uptake of water and solutes.
Also at Wisconsin, work with Ed Miller and his student Bill Herkelrath suggested that substantial resistance was encountered between the soil and root xylem, even though the permeability of the soil was quite high at the average water content of the soil in the experiments. This result was at variance with previous diffusion-based models, which predicted up to 8 times higher water uptake rates than they observed under these ￼￼conditions. the researchers developed an alternative model that assumed the loss of contact area between soil and root was responsible for the discrepancy, something that had never before been proposed.
Source: Wilford Gardner obituary
- Gardner, W.R., 1956. Representation of Soil Aggregate-Size Distribution by a Logarithmic-Normal Distribution1, 2. Soil Science Society of America Journal, 20(2), pp.151-153.
- Richards, L.A., Gardner, W.R. and Ogata, G., 1956. Physical processes determining water loss from soil. Soil Science Society of America Journal, 20(3), pp.310-314.
- Gardner, W.R., 1958. Some steady-state solutions of the unsaturated moisture flow equation with application to evaporation from a water table. Soil science, 85(4), pp.228-232.
- Gardner, W.R., 1956. Calculation of capillary conductivity from pressure plate outflow data. Soil Science Society of America Journal, 20(3), pp.317-320.
- Gardner, W.R. and Mayhugh, M.S., 1958. Solutions and tests of the diffusion equation for the movement of water in soil. Soil Science Society of America Journal, 22(3), pp.197-201.
- Gardner, W.R. and Fireman, M., 1958. Laboratory studies of evaporation from soil columns in the presence of a water table. Soil Science, 85(5), pp.244-249.
- Gardner, W.R., 1959. Solutions of the flow equation for the drying of soils and other porous media. Soil Science Society of America Journal, 23(3), pp.183-187.
- Gardner, W.R., 1960. Dynamic aspects of water availability to plants. Soil science, 89(2), pp.63-73.
- Gardner, W.R. and Hillel, D.I., 1962. The relation of external evaporative conditions to the drying of soils. Journal of Geophysical Research, 67(11), pp.4319-4325.
- Gardner, W.R. and Ehlig, C.F., 1963. The influence of soil water on transpiration by plants. Journal of Geophysical Research, 68(20), pp.5719-5724.
- Gardner, W.R., 1964. Relation of root distribution to water uptake and availability. Agronomy Journal, 56(1), pp.41-45.
- Gardner, W.R. and Nieman, R.H., 1964. Lower limit of water availability to plants. Science, 143(3613), pp.1460-1462.
- Gardner, W.R. and Ehlig, C.F., 1965. Physical aspects of the internal water relations of plant leaves. Plant physiology, 40(4), p.705.
- Gardner, W. R., Movement of nitrogen in soil. In: Soil Nitrogen, W. V. Bartholomew and Francis E. Clark, eds., pp. 550-562. Madison, WI: American Society of Agronomy.
- Hillel, D. and Gardner, W.R., 1969. STEADY INFILTRATION INTO CRUST-TOPPED PROFILES. Soil Science, 108(2), pp.137-142.
- Black, T.A., Gardner, W.R. and Thurtell, G.W., 1969. The prediction of evaporation, drainage, and soil water storage for a bare soil. Soil Science Society of America Journal, 33(5), pp.655-660.
- Hillel, D. and Gardner, W.R., 1970. Transient infiltration into crust-topped profiles. Soil Science, 109(2), pp.69-76.
- Gardner, W.R., Hillel, D. and Benyamini, Y., 1970. Post‐Irrigation Movement of Soil Water: 1. Redistribution. Water Resources Research, 6(3), pp.851-861.
- Dalton, F.N., Raats, P.A.C. and Gardner, W.R., 1975. Simultaneous uptake of water and solutes by plant roots. Agronomy Journal, 67(3), pp.334-339.
- W.A. Jury, Gardner, W. R., P. Saffigna, and C. B. Tanner. Model for predicting simultaneous movement of nitrate and water through a loamy sand. Soil Sci. 122: 36-43.
- Herkelrath, W.N., Miller, E.E. and Gardner, W.R., 1977. Water uptake by plants: I. Divided root experiments. Soil Science Society of America Journal, 41(6), pp.1033-1038.
- Herkelrath, W.N., Miller, E.E. and Gardner, W.R., 1977. Water uptake by plants: II. The root contact model. Soil Science Society of America Journal, 41(6), pp.1039-1043.
- Skopp, J., Gardner, W.R. and Tyler, E.J., 1981. Solute movement in structured soils: Two-region model with small interaction. Soil Science Society of America Journal, 45(5), pp.837-842.
- Warrick, A.W. and Gardner, W.R., 1983. Crop yield as affected by spatial variations of soil and irrigation. Water Resources Research, 19(1), pp.181-186.
- Gardner, W.R., 1991. Modeling water uptake by roots. Irrigation science, 12(3), pp.109-114.