Soil oxygen enables aerobic respiration of plant roots and
soil micro- and meso-flora and fauna. Its availability can
be limited by soil wetness, compaction, discontinuous
pores, or high respiration in moist soil due to elevated soil
temperature or incorporation of fresh organic substrate.
With oxygen depletion, soil redox potential shifts from
oxidative to reducing conditions, hampering plant growth
because of less efficient metabolic pathways and release
into soil of toxic by-products of reduction chemistry or
anaerobic respiration. Several texts are excellent sources
for fundamental soil aeration concepts (1-3).
Measurements of soil aeration fall into three categories:
"capacity," volume of gas-filled void space; "Intensity,"
partial pressure or concentration of oxygen (or other gases)
in the voids; and "transport rate," the rapidity at which
oxygen can be supplied to a point in the soil. Measurement
difficulty increases in the order capacity < intensity
< rate, as do the value and insight of the measurements
