substances develop that are much less useful in soil. Under airless
conditions much nitrate is permanently lost. The odiferous wastes of
anaerobes also includes hydrogen sulfide (smells like rotten eggs),
as well as other toxic substances with very unpleasant qualities.

Heaps built with significant amounts of coarse, strong, irregular
materials tend to retain large pore spaces, encourage airflow and
remain aerobic. Heat generated in the pile causes hot air in the
pile's center to rise and exit the pile by convection. This
automatically draws in a supply of fresh, cool air. But heaps made
exclusively of large particles not only present little surface area
to microorganisms, they permit so much airflow that they are rapidly
cooled. This is one reason that a wet firewood rick or a pile of
damp wood chips does not heat up. At the opposite extreme, piles
made of finely ground or soft, wet materials tend to compact, ending
convective air exchanges and bringing aerobic decomposition to a
halt. In the center of an airless heap, anaerobic organisms
immediately take over.

Surface Area of One Gram of Soil Particles

Particle Size Diameter of Number of Surface Area
Particles in mm Particles per gm per square cm

Very Coarse Sand 2.00-1.00 90 11
Coarse Sand 1.00-0.50 720 23
Medium Sand 0.50-0.25 5,700 45
Find Sand 0.25-0.10 46,000 91
Very Fine Sand 0.10-005 772,000 227
Silt 0.05-0.002 5,776,000 454