Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/12/2004
Publication Date: 5/15/2005
Citation: Johnson, D.O., Arriaga, F.J., Lowery, B. 2005. Automation of a falling head permeameter for rapid determination of hydraulic conductivity on multiple samples. Soil Science Society of America Journal. 69(3):828-833. Interpretive Summary: Soil management can be improved if spatial variability of soil hydraulic conductivity is taken into account. To accommodate for the large number of samples needed to assess spatial variability of large fields, a laboratory soil hydraulic conductivity device was automated with the use of pressure transducers. This automated unit allows for several samples to be processed with minimal oversight compared with frequent manual readings by a laboratory technician. Values obtained using the automated method were compared to values obtained for the same cores using the traditional manual technique and there were no statistical differences. The potential exists to expand this instrument and process an even larger number of samples at a time. This automated system can increase the amount of soil hydraulic conductivity data that can be obtained, increasing the understanding of spatial variability of fields and help improve soil management.
Technical Abstract: Soil management can be improved if soil spatial variability is taken into account. We initiated a study to quantify spatial variability of soil hydraulic properties. Initially we focused on hydraulic conductivity of saturated soil (Ks) by horizons. In situ Ks measurements made in the Ap, Bt, and till horizons showed significant differences between horizons within a given location and spatial position. The 2-ha study area consisted of three soils and in situ sampling was very time consuming. To accommodate the large number of samples needed to assess spatial variability of the 2-ha area, further sampling was done via 7.62-cm diameter by 7.62-cm long soil cores for laboratory analyses. For these samples, we developed an automated falling head permeameter by attaching pressure transducers to falling head permeameters to measure Ks of soil cores in the laboratory. To test this method, sixty soil core samples were taken from two additional locations, 30 from a sandy soil and 30 from a silt loam soil. The Ks values from sand ranged from 1.02 x 10-5 to 2.78 x 10-6 cm s-1, and values from silt loam ranged from 2.78 x 10-7 to 2.48 x 10-8 cm s-1. The automated unit allows for six samples to be processed with minimal oversight compared with one sample being read manually requiring frequent observations. When values obtained using the automated method were compared to values obtained for the same cores using the manual technique, there was no statistical difference at the 95% level.