Aeration in Soil

Poor aeration can also be due to restricted flow of air from the atmosphere into soil pores. Most of the gaseous interchange with the atmosphere occurs through diffusion, which is hampered by a lack of macro pores in the soil. On heavily textured top soils and in compact sub soils, the rate of gaseous movement is particularly slow.

Adobe soil is heavy clay, sometimes with an admixture of silt. It is likely to be rich in minerals, but almost entirely deficient in humus. Of all soil types it is one of two (sand is the other) that will benefit most conspicuously from organic gardening methods.

Being heavy, it requires aeration. In its natural state it will contain no earthworms (ants and tunneling gophers aerate it for the native vegetation).

The earthworm will burrow down six feet and more, leaving its passageways as means for the entry of air. Applications of organic matter automatically multiply the earthworm population. In well-run organic farms and gardens there should be millions of earthworms per acre.

The subsoiler made by many tractor manufacturers is pulled through the soil at depths of ten to 20 inches, shattering hard pans and improving aeration. The soil must not be wet when subsoiling is going on or the hard pan will not be broken.

The composition of soil air differs somewhat from that of the atmosphere above ground. In the soil much of the air is dissolved in the soil water, but as such it is available to the needs of plants. Humidity is greater in the soil, a condition necessary for the optimum functioning of soil organisms.

Even the vital iron, which has been there all the time (the red in adobe is iron oxide), and the locked-up phosphates may be freed to some extent.

A waterlogged condition is so detrimental to plant growth that even a short period may seriously endanger some plants. This may occur either in poorly drained soils composed of fine particles or in well-drained soil if enough water is rapidly applied. Prevention of this type of poor aeration necessitates removing water from the land, either by controlled runoff or drainage; the latter can be particularly effective.