Aeration of clayey soils by injecting air through subsurface drippers: Lysimetric and field experiments

We examined the effects of air injection into clayey-soil, with and without a perforated sphere around the dripper, on oxygen concentrations and pepper yields in a barrel experiment, and on soil oxygen concentrations and stem growth of young mango trees in a field experiment. The perforated sphere was intended to reduce soil resistance to air flow and to enhance the efficiency of air spreading in the soil. The main findings were that injecting atmospheric air did not contribute much to aeration of soils with high existing oxygen concentrations, i.e., about 80% of the atmospheric 21%, in the barrel experiments, and did not contribute at all in the field experiment, where oxygen concentration was about 95% of atmospheric. Furthermore, it was found that an oxygen concentration of about 80% did not decrease pepper yield in the absence of other stresses such as salinity or nutrients deficiency. A perforated sphere increased soil oxygen concentration when both water and air were applied through the sphere. A positive effect of air injection on pepper yields was found in soils with high volumetric water contents, i.e., average above 0.4 throughout the growth period. Conversely, air injection decreased pepper yields in barrels where water contents were lower.