Look out at the Campbell tract, west of Highway 113 and what
do you see? Ag land, right?
Well, not exactly. Lying underground is a sophisticated research facility called a lysimeter that has been collecting wind pattern and evaporation data on crops for nearly 40 years.
Its sensitive measuring capabilities and importance to campus research prompted Planning and Budget this spring to move the site of the proposed waste water treatment plant elsewhere.
"The measurement is so fine--at microlevels-- that the researchers were concerned that a local phenomenon like the plant would override the regional trend," said campus planner Bob Segar.
Although the lysimeter's data depend on precise field conditions, its basic principles are not all that complex. The lysimeter is much like a potted plant that sits in the ground, with its top at field level. Instead of just one plant growing in it, the lysimeter can accommodate hundreds, according to Kyaw Tha Paw U, a professor in land, air and water resources who has headed up many of the lysimeter studies since 1984.
"People who drive by or even people doing work near our section might not know it's there," Paw U said.
The lysimeter was developed by Paw U's colleague Bill Pruitt, who supervised the research until he retired in 1984. Pruitt, who still lives in Davis, was responsible for the equipment's construction in 1958.
"For a while it was the largest lysimeter of its type in the world," Paw U said. "It was used for the first pioneering experiments for establishing the fundamental relationships between water loss and heat transfer that are still used today."
The lysimeter has been used in hundreds of experiments throughout its 38-year history, and the data provided are applicable to a number of fields such as organic farming, environmental toxicology, botany, engineering and atmospheric science. As a result, several interdisciplinary collaborations have relied on the lysimeter for data.
"We often work with hydrology and plant science," said Alistair Moles, a graduate student who has worked with Paw U for three years. "Right now we're studying water stress, which means depriving plants of water and seeing what kinds of mechanisms they use to allocate their energy."
Actually, two types of lysimeters exist at the Campbell tract off Hutchison Drive.
One, a weighing lysimeter, has a tunnel underneath it housing a precise, 45-metric-ton scale that measures water loss from the soil and plants to tenths of a pound.
The weighing lysimeter measures nearly 20 feet in diameter and descends 6 1/2 feet underground. Its tunnel underneath is accessible via a hatch that opens up onto the field.
The other lysimeter is a floating lysimeter, since the container of soil and crops floats on a thin layer of water. When wind buffets the crops above, the displacement of the lysimeter reflects the wind's strength, which is measured. Although Paw U says the weighing lysimeter will never become obsolete because its principles are so basic -- water loss equals weight loss -- the floating lysimeter has been dated somewhat by new technology like the sonic anemometer, a device they are testing right now.
The
anemometer measures the extent sound waves are disturbed by wind currents
and temperature. The data are then analyzed in the tunnel below on a computer.
"It's used to replace the floating lysimeter," Paw U said. "The sonic anemometer and the lysimeters can also be used in conjunction with each other to help confirm each other's readings."
According to graduate student Moles, the rapidity of the sonic waves makes the anemometer a good resource. "It's very sophisticated equipment," he said. "The faster the speed, the more accurate the information from the data becomes."
While the sonic anemometer may be cutting-edge technology, crop scientists have been using lysimetry for some 300 years, according to A. Aboukaled's Lysimeters. The first was built in 1688 by De la Hire, a mathematician and meteorologist under King Louis XIV. Over the centuries, European and American scientists expanded lysimetry to encompass more aspects of crop growth, and within the last two decades, lysimeters have become instrumental in the study of atmospheric science.
"Using the lysimeter we found that heat and water loss from plants are controlled by the action of wind shearing," Paw U said. "Wind shear has caused airplanes to crash in the past, but in crops it's on a much smaller scale and it's not associated with clouds.
"We also found at the Davis lysimeter that many equations that were devised for conditions above the plants do not hold true for below the crop canopy," he added. The lysimeter studies receive support from the Department of Energy, the U.S. Geological Survey and the U.S. Department of Agriculture, among other organizations. Through a collaboration with the National Aeronautics and Space Administration in 1994, the space shuttle Endeavour photographed the site with radar from outer space, demonstrating that a 300-year-old science is still relevant.
"There's a lot of science in crop science," Paw U said. "Sometimes people look out at a field and just think, 'Hey there's some corn growing!' but there's a lot more to it than that."
Jessie Seyfer, a senior physiology major, is the science writing intern
for the News Service.
(Tony Noveloso/Axiom Photo)
