Kr. Close et al., TENSION INFILTROMETER CONTACT INTERFACE EVALUATION BY USE OF A POTASSIUM-IODIDE TRACER, Transactions of the ASAE, 41(4), 1998, pp. 995-1004
Tension infiltrometer (disc permeameter) measurements may be adversely
affected by small variations in experimental procedures. Published te
nsion infiltrometer procedures are not adequate for all tension infilt
rometer studies. A potassium iodide solution was infiltrated through t
ension infiltrometers into packed soil columns in PVC tubing to evalua
te the effect of permeameter contact variations at the silica sand/mem
brane interface. Packed columns minimized the effects of macropores, s
oil type variability and layering, allowing improved setup procedures
to be developed. The spatial distribution of the potassium iodide solu
tion on horizontal cross-sections of the column, at the surface, and v
arious depths, was examined wing a starch and bleach technique which f
orms a blue-black potassium iodide-starch-bleach complex. The dye stai
ning technique allowed assessment of the causes of variability Tension
infiltrometer setup procedures were developed which resulted in repro
ducible tension infiltration curves and patterns as indicated by a pot
assium iodide tracer (during the initial 10-min phase). Despite using
improved permeameter setup procedures there was non-uniform wetting an
d infiltration of packed columns of a sandy loam soil and a sandy clay
loam soil at tensions of 0.6 kPa and 1.2 kPa, respectively. This was
attributed to non-uniform wetting of the contact silica sand at the me
mbrane interface. Assumptions that the flux through the silica sand co
mpensates for imperfect membrane contact may not be justified The deve
loped procedures will aid other researchers using tension infiltromete
rs to decrease variability between replicates.