Vl. Quisenberry et al., SPATIAL-DISTRIBUTION OF WATER AND CHLORIDE MACROPORE FLOW IN A WELL-STRUCTURED SOIL, Soil Science Society of America journal, 58(5), 1994, pp. 1294-1300
Macropore how is recognized as an important component of water and sol
ute transport in many soils. Our understanding of its magnitude and si
gnificance is not well developed. The objective of this experiment was
to measure the effect of application rate on the magnitude and spatia
l distribution of macropore how in a Maury silt loam (fine, mixed, mes
ic Typic Paleudalf). An undisturbed block of soil (32.5 by 32.5 by 32.
5 cm) was obtained and placed on a specially designed apparatus that a
llowed effluent to be collected under - 2.0 kPa vacuum and separated i
nto 100 cells. Water tagged with Cl- was applied by 100 needles, 0.25-
mm i.d., which were positioned directly above the 100 collection cells
. Approximately 7.5 cm of solution was applied at four application rat
es: 3.14, 1.97, 1.23, and 0.5 cm h(-1). A large fraction of the water
and solute moved through a small percentage of the total soil for all
application rates: 50% of the water and Cl- were collected in <20 and
10%, respectively, of the cells. Displacement of antecedent water by a
pplied water was much higher for the 0.5 cm h(-1) application rate tha
n for the higher three rates. The position and spatial pattern of macr
opore flow remained fairly constant for the three highest how rates. A
reas of high soil water flow and high Cl- concentrations were clustere
d, not randomly distributed across the column. We believe these findin
gs support our hypotheses that how takes place in the same network of
pores for similar rainfall events and that interpedal voids between te
rtiary structural units are important pathways of