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Title: A POINT SOURCE METHOD FOR RAPID ESTIMATION OF SOIL HYDRAULIC AND CHEMICAL TRANSPORT PROPERTIES

Author
item AL-JABRI, A - IOWA STATE UNIVERSITY
item HORTON, R - IOWA STATE UNIVERSITY
item Jaynes, Dan

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2001
Publication Date: 1/5/2002
Citation: Al-Jabri, A., Horton, R., Jaynes, D.B. 2002. A point source method for rapid estimation of soil hydraulic and chemical transport properties. Soil Science Society of America Journal. 66:12-18.

Interpretive Summary: To determine the fate and transport of water, nutrients, and other agricultural chemicals applied to fields, scientists need basic information about the hydraulic and chemical properties of soils. However, current methods for measuring these soil properties are costly and slow, which prevents the routine collection of this valuable data and limits its availability. We developed and tested a new approach for simultaneously measuring both soil hydraulic and chemical transport properties with a simple, rapid measurement system that is adaptable for use in the field. Our findings showed that the new method is easy to use, reproducible, and provides measurements that are equal in accuracy to current, more expensive and time consuming techniques. The new method will be of interest to other soil scientists and technicians and should lead to greater availability of critical soil information for scientists, regulators, and others.

Technical Abstract: Hydraulic and chemical transport properties are needed for accurate prediction of water and chemical movement through the vadose zone. Field methods used to estimate such properties are often hampered by extensive labor and time constraints. One objective of this study was to develop and evaluate an experimental setup and a procedure for a point source method that facilitates rapid and simultaneous measurements of soil hydraulic and chemical transport properties at multiple locations. Another objective was to evaluate the point source method in determining such properties by comparing the parameters produced by the point source method with those produced by ponded and tension infiltrometers. The experimental setup consisted of three dripper lines equipped with pressure-compensating drippers. Hydraulic properties from the point source method were determined by applying four consecutive discharge rates on the soil surface and measuring their corresponding steady-state saturated areas. Chemical transport parameters, immobile water fraction and mass exchange coefficient, were determined by applying a sequence of conservative fluorobenzoate tracers. The point source method gave consistent and reliable estimates for both sets of properties. Except for the mass exchange coefficient, there were no significant differences between the two procedures (point source vs. infiltrometers) in determining both sets of properties.