Abstract
1. Evidence, both direct and indirect, has been adduced to prove that the air is sufficient both qualitatively and quantitatively to supply all the nutritional requirements of plants, independently of the soil or soil bacteria.2. The fertility of an undisturbed soil lies chiefly in the surface inch or two and is due to adsorption of plant nutrients from the air by organic and inorganic colloids, such nutrients being carried down to the roots of the growing crop by rain.

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