Soil physical conditions affecting seedling root growth. II. Mechanical impedance, aeration and moisture availability as influenced by grain-size distribution and moisture content in silica sands | Soil physical conditions affecting seedling root growth. II. Mechanical impedance, aeration and moisture availability as influenced by grain-size distribution and moisture content in silica sands. [Peas]
1972
Warnaars, B.C. | Eavis, B.W.
Pea, corn, and grass seedling root growth in five sands varying in grain-size distribution, packed dry then maintained at six matric potentials, varied according to mechanical impedance and aeration. Mechanical impedance restricted root elongation in every treatment including the finer sands in which longest roots were found, but it was greatest in the coarse sands, where crooked swollen roots similar in shape to the pore channels were produced. Straight evenly tapered roots were formed in the fine sands due to a more balanced stress distribution over the root tip. Interpretations of penetrometer measurements differed in coarse and fine sands. 'Aeration effects' were distinguished from mechanical impedance effects by comparing the root lengths expected (mechanical impedance and aeration acting together), and they occurred in sands with less than 25 percent gas-filled pore space. No effect due to water availability could be found.
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