Lorenzo A. Richards
Encyclopedia
Lorenzo Adolph Richards or known as Ren was one of the 20th century’s most influential minds in the field of soil physics
. Richards was born on April 24, 1904, in the town of Fielding, Utah
, and received a B.S. and M.A. degree in Physics from Utah State University
. His PhD thesis, completed at Cornell University
in 1931 and entitled Capillary conduction of liquids through porous mediums, was arguably one of the best known in the field of soil physics. Following his time at Cornell, and a brief stint at Iowa State University
, Richards spent the most part of his working life engaged in soil physics research at the United States Department of Agriculture
Salinity Laboratory in Riverside, California
.
to describe water movement in unsaturated soils. In this research, Richard described a partial differential equation, now commonly known by as the Richards equation
.
One of Richards' key interests was the energy status of soil water, and he led the way in developing new and improved methods of measuring soil water potential
. Early in his career, Richards recognised the importance of capillary
potential to plant-soil relations, and described the principles, construction and operation of the tensiometer
. Richards also proposed the tension plate apparatus for determining capillary potential in soil. The tensiometer was developed from the idea of using a semi-permeable, porous ceramic material to balance a pressure potential against a matric potential; once equilibrium had established, the matric potential of the soil could be determined by balancing the pressure potential.
Richards made continual improvements to his original design and the operation of the tensiometer. The problem of measuring capillary potential beyond the range of the tensiometer was a further research interest of Richards. In 1941 he published a paper describing the pressure-membrane apparatus. Although Richards claimed the primary purpose of the apparatus was the extraction of soil solution for salinity analysis, he also pointed out its potential for application to energy studies
(−1/3 bar, or −33 J/kg) and permanent wilting point
(−15 bar, or −1500 J/kg) were determined through experimental work by Richards and his colleagues.
Over forty working years, Lorenzo Richards contributed much to knowledge of the energy status and transport of water in soil. He developed much of the modern apparatus and methodology used for study of soil water, hence playing a pivotal role in the transformation of knowledge on this subject from the qualitative stage to one based on measurements and mathematics.
Soil physics
Soil physics is the study of soil physical properties and processes. It is applied to management and prediction under natural and managed ecosystems. Soil physics deals with the dynamics of physical soil components and their phases as solids, liquids, and gases. It draws on the principles of...
. Richards was born on April 24, 1904, in the town of Fielding, Utah
Fielding, Utah
Fielding is a town in Box Elder County, Utah, United States. The population was 455 at the 2010 census.-Geography:Fielding is located at ....
, and received a B.S. and M.A. degree in Physics from Utah State University
Utah State University
Utah State University is a public university located in Logan, Utah. It is a land-grant and space-grant institution and is accredited by the Northwest Commission on Colleges and Universities....
. His PhD thesis, completed at Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
in 1931 and entitled Capillary conduction of liquids through porous mediums, was arguably one of the best known in the field of soil physics. Following his time at Cornell, and a brief stint at Iowa State University
Iowa State University
Iowa State University of Science and Technology, more commonly known as Iowa State University , is a public land-grant and space-grant research university located in Ames, Iowa, United States. Iowa State has produced astronauts, scientists, and Nobel and Pulitzer Prize winners, along with a host of...
, Richards spent the most part of his working life engaged in soil physics research at the United States Department of Agriculture
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
Salinity Laboratory in Riverside, California
Riverside, California
Riverside is a city in Riverside County, California, United States, and the county seat of the eponymous county. Named for its location beside the Santa Ana River, it is the largest city in the Riverside-San Bernardino-Ontario metropolitan area of Southern California, 4th largest inland California...
.
Research
Richards' PhD thesis represented the first decisive progress beyond the work of Edgar Buckingham in the extension of Darcy's lawDarcy's law
Darcy's law is a phenomenologically derived constitutive equation that describes the flow of a fluid through a porous medium. The law was formulated by Henry Darcy based on the results of experiments on the flow of water through beds of sand...
to describe water movement in unsaturated soils. In this research, Richard described a partial differential equation, now commonly known by as the Richards equation
Richards equation
The Richards equation represents the movement of water in unsaturated soils, and was formulated by Lorenzo A. Richards in 1931 . It is a non-linear partial differential equation, which is often difficult to approximate since it does not have a closed-form analytical solution.Darcy's law was...
.
One of Richards' key interests was the energy status of soil water, and he led the way in developing new and improved methods of measuring soil water potential
Water potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension...
. Early in his career, Richards recognised the importance of capillary
Capillary
Capillaries are the smallest of a body's blood vessels and are parts of the microcirculation. They are only 1 cell thick. These microvessels, measuring 5-10 μm in diameter, connect arterioles and venules, and enable the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste...
potential to plant-soil relations, and described the principles, construction and operation of the tensiometer
Tensiometer
A Tensiometer as it applies to physics is an instrument used to measure the surface tension of liquids.-Goniometer/Tensiometer:...
. Richards also proposed the tension plate apparatus for determining capillary potential in soil. The tensiometer was developed from the idea of using a semi-permeable, porous ceramic material to balance a pressure potential against a matric potential; once equilibrium had established, the matric potential of the soil could be determined by balancing the pressure potential.
Richards made continual improvements to his original design and the operation of the tensiometer. The problem of measuring capillary potential beyond the range of the tensiometer was a further research interest of Richards. In 1941 he published a paper describing the pressure-membrane apparatus. Although Richards claimed the primary purpose of the apparatus was the extraction of soil solution for salinity analysis, he also pointed out its potential for application to energy studies
Other work
Another important element of Richard’s work was in the field of soil-water-plant relations, and led to the standardisation of characteristic soil-water properties. Together with scientists at the USDA Salinity Laboratory in Riverside, Richards correlated water content at certain water potential values with then current soil water parameters. The currently accepted moisture potential values defining the lower and upper limits for plant growth; at field capacityField capacity
Field capacity is the amount of soil moisture or water content held in soil after excess water has drained away and the rate of downward movement has materially decreased, which usually takes place within 2–3 days after a rain or irrigation in pervious soils of uniform structure and texture...
(−1/3 bar, or −33 J/kg) and permanent wilting point
Permanent wilting point
Permanent wilting point or wilting point is defined as the minimal point of soil moisture the plant requires not to wilt. If moisture decreases to this or any lower point a plant wilts and can no longer recover its turgidity when placed in a saturated atmosphere for 12 hours...
(−15 bar, or −1500 J/kg) were determined through experimental work by Richards and his colleagues.
Over forty working years, Lorenzo Richards contributed much to knowledge of the energy status and transport of water in soil. He developed much of the modern apparatus and methodology used for study of soil water, hence playing a pivotal role in the transformation of knowledge on this subject from the qualitative stage to one based on measurements and mathematics.