Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2009
Publication Date: 6/16/2011
Citation: Palmer, R.E., Meisinger, J.J., Magette, W.L. 2011. Undisturbed soil columns for lysimetry I. Collection, field testing and construction. Applied Engineering in Agriculture. 27(3):379-389. Interpretive Summary: The study of the movement of nutrients through soils is an important area of soil science, particularly when evaluating the water quality impacts of nutrient management practices, cover crops, or conservation tillage. Maintaining the soil's structural characteristics is of particular concern since many transport process involve movement through cracks, worm holes, or old root channels. A simple and inexpensive method of excavating large, 18 inch diameter by 3 feet long, undisturbed soil cores was developed which involves field excavation around an intact core, placing a PVC casing around the core, and grouting between the soil and PVC with a 50-50 mix of bentonite clay and sand. The structural integrity of the encased core was evaluated in the field by its ability to transmit air under low pressure, using an air permeability technique. Encased cores were then removed from the field, secured to a specially designed floating platform, and transported 60 miles to the Beltsville Agriculture Research Center. After transportation the cores were again tested for air permeability. Results showed that seven out of eight cores were successfully moved from the field site to the research site. A series of seven independent porous ceramic cup extractors were also fitted to the bottom of each soil column to collect percolate when hooked into an on-site vacuum system, which transformed the columns into small lysimeters capable of studying solute transport processes in soils or water quality. This investigation is important to soil scientists, applied engineers and environmental scientists because it has shown that it is possible to secure, transport, and test the structural integrity of large undisturbed soil columns and to outfit them with a vacuum system for collecting percolate that can be used for nitrogen leaching and water quality research.
Technical Abstract: Methods to obtain undisturbed soil columns are vital to the study of solute transport in soils. Of particular concern is the maintenance of the soil's structural integrity in order to preserve preferential flow processes. A simple and inexpensive method of excavation was developed for 41 cm diameter by 100 cm long undisturbed soil columns. A 50:50 mixture of bentonite clay and sand was used to encase and seal the soil column within a 42 cm internal diameter by 100 cm long PVC casing. Air permeability was successfully used to evaluate the integrity of the undisturbed soil columns before and after transportation. A steel frame fitted with a floating platform was designed which successfully transported seven of eight soil columns over a distance of 102 km. The soil columns were fitted with a series of seven independent porous ceramic cup extractors that were hooked to an on-site vacuum system, which transformed the columns into small lysimeters capable of studying solute transport processes in soils or water quality. Results of this research demonstrate that it is possible to secure, transport, and test the structural integrity of undisturbed soil columns and to equip them with a tension drained collection system suitable for solute transport or water quality research.