Influence of Soil Water Matric Potential and Resistance to Penetration on Corn Root Elongation

Abstract

A study of the interacting effects of soil bulk density and soil water matric potential on resistance to penetration and on corn root elongation showed that for any level of resistance, elongation was further restricted as potential decreased (suction increased). This was explained through the effect of matric potential on plant turgor, which in turn affects the ability of the root to overcome resistance. At negligible resistance, elongation was greater in a clay loam soil than over a range of equivalent osmotic potentials in solution, indicating that moisture transport in the soil apparently did not restrict moisture supply to the root. It is suggested that the presently accepted upper limits of resistance for corn growth may be too high.

Physical root–soil interactions

“…The measured soil strength depends on the tools and methods, leading to a large range of values and an apparent inconsistency. For instance maize RER was reduced by 50% for a penetrometer resistance ranging from 0.2 to 2 MPa depending on the study [41,44,45]. RER sensitivity to soil strength, that is the RER reduction relative to unconstrained state, seems to be species-specific.…”

“…In field [39,40] as well in lab experiments with soil compacted in a core [41,42] or with pressure cells [43], root elongation rate (RER, as improperly called by biologists since it is a velocity, mm h -1 ) varies inversely with soil strength. The measured soil strength depends on the tools and methods, leading to a large range of values and an apparent inconsistency.…”

Ramification des racines nodales primaires du maïs (Zea mays L). Données de structure et de cinétique

“…En effet, les travaux entrepris au champ, échelle de référence pour l'agronome, ont souvent été limités à l'étude de l'influence d'une condition de milieu sur un paramètre descriptif de l'enracinement : c'est ainsi que, par exemple, les vitesses d'élongation ont été exprimées en fonction, soit de la température (Blacklow, 1972) soit du potentiel matriciel (Mirreh et Ketcheson, 1973). Les (Lungley, 1973;Diggle, 1988 (Picard et al, 1985) (Bohm, 1979) (May et al, 1965;Brouwer, 1981;Geisler et (Picard et al, 1985) (Wang, 1983).…”

Plant exudates improve the mechanical conditions for root penetration through compacted soils

“…where R is rate of root elongation (mm day −1 ), R max maximum rate of maize root elongation of 26 mm day −1 (Mirreh and Ketcheson 1973), ψ 0 is water potential in MPa, ψ w is the wilting point water potential i.e. -1.5 MPa, Q P is the cone penetration in MPa and Q 1/2 is the cone penetration resistance that reduces relative root elongation rate to one-half (taken as 1.3 MPa for maize).…”