Soil Aeration as a Factor in Growth and Root Development of Plants.

Abstract

The soil in which certain aquatic and terrestial angiosperms were growing was slowly aerated daily for a period of one-half to 5 hours by means of compressed air supplied through perforated coils imbedded 8 inches below the surface. Helianthus annuus, Triticum vulgare, Glycine soja, Linum usitatissimum and cuttings of Vitis vulpina were grown in sand and in loam. At the age of 2 months conspicuous differences were apparent in aerated and unaerated plants on the same soil as well as between plants similarly treated but in different soils. As might be anticipated aeration did not produce the same effects in plants grown in loam and in sandy soil. Structural differences occurred in both tops and root systems, but especially the latter.

In general, roots in the aerated soils were distinctly fibrous in character, more numerous and longer, forming branches of secondary and tertiary rank. Total surface in aerated roots was twice or more that of control roots, but the root hair zone was smaller. Fewer hairs developed and these in turn were not as long-lived in aerated plants as in the controls due to the more rapid elongation of the aerated roots. Vascular elements a few inches above the root hair zone were less developed in aerated roots.

The striking effect of aeration on tops was acceleration of growth in early stages, attributable to increased length of basal internodes rather than to an increase in the number. Contrast in internodal distance diminished noticeably, however, above the median nodes and there was little or no difference in size of internodes near the tips. Elongation continued in controls after aerated plants had started to flower. This response tended to reduce size differences when mature plants of both groups were compared.