Soil Strength and Aeration Effects on Root Elongation
1975
Voorhees, W. B. | Farrell, D. A. | Larson, W. E.
Primary root elongation rates of pea seedlings (Pisum sativa L. ‘Alaska’) and soil resistance to penetration of a probe were measured in remolded cores of sandy loam and clay soils over a soil water suction range of 0.1–1.0 bar. Physical soil resistance was varied by varying soil bulk density and water content. Primary root elongation was more closely correlated with soil resistance to a 10° probe than a 60° probe. It was also more closely correlated with soil resistance normal to the probe, which does not include soil-metal friction, than with total point resistance which does include the friction component. While soil-metal friction may not be equivalent to soil-root friction, this correlation suggests that friction between root cap and soil may be negligible. About 73% of the variation in primary root elongation was accounted for using normal point resistance to a 10° probe and including the effects of air-filled pores in the bulk soil. Primary root elongation was most sensitive to air-filled porosity at low levels of soil physical resistance. Root length density increased as soil resistance increased due to increased production of first-order laterals and decreased rooting depth.
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