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  • Penetrometer  (3)
  • Penetration  (2)
  • Soil strength  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The behaviour of roots encountering cracks in soil (1984)
    Springer
    Plant and soil 77 (1984), S. 141-149 
    Details
    ISSN: 1573-5036
    Keywords: Cracks ; Crack width ; Lateral roots ; Pea ; Penetration ; Penetrometer ; Rape ; Remoulded soil ; Roots ; Safflower ; Seminal axes ; Soil strength ; Undisturbed soil ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experimental methods are described for observing the behaviour of roots encountering cracks in soil. The proportions of roots which enter a second soil block after crossing a crack of known width were measured. Soil strength was measured with a penetrometer. Results are presented for the proportions of seminal roots of wheat and primary lateral roots of pea which enter moulded soil of various strengths after crossing cracks. Results are also presented for the proportions of seminal roots of pea, rape and safflower which enter undisturbed soil after crossing cracks. It was found that, in all cases, the proportion of roots penetrating the second soil block decreased with increasing crack width and increasing soil strength. Also, a smaller proportion of thinner roots penetrated the second soil block than thicker roots under similar conditions. Root diameter in the cracks was influenced by both crack width and soil strength, and an empirical equation is presented to describe this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182918
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of penetrometer pressures and the pressures exerted by roots (1981)
    Springer
    Plant and soil 61 (1981), S. 351-364 
    Details
    ISSN: 1573-5036
    Keywords: Confined cores ; Penetrometer ; Remoulded soil ; Root growth pressure ; Tensile strength ; Unconfined cores ; Weathering ; Wetting and drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Previous work is reviewed in which the ratio of the pressures required for soil penetration by roots and penetrometers are compared. It appears that this ratio can vary from about 2 to 8 depending on conditions. However, there is very little experimental evidence and most of the work has been inferential. Direct measurements are reported for the stresses exerted by a 1 mm diameter penetrometer probe and by the roots of pea seedlings when penetrating Urrbrae fine sandy loam. Six soil conditions were used: (non-weathered remoulded soil cores + artificially weathered remoulded soil cores + undisturbed field clods) × (confined + unconfined cores or clods). The confinement treatment was to test for any effects of additional restraint to cylindrical root expansion. The weathering and field clod treatments were to test the hypothesis that root elongation is facilitated by tensile failure ahead of the root tip. The principal conclusions are as follows. The laboratory weathering treatment reduced the soil tensile strength by 25%. This resulted in a small but significant reduction in the pressure for root penetration into confined cores. Compared with remoulded non-weathered cores, field clods had a 2 to 3 fold greater penetrometer resistance and a 50% lower tensile strength. The force required for root penetration into unconfined field clods was only 10% greater than for unconfined non-weathered cores. For the former (which is closest to field conditions) the penetrometer had to exert a pressure 5.1 times greater than a root tip in order to penetrate the soil. Penetrometer penetration pressure was independent of probe diameter in the 1–2 mm range in the soil used. Core confinement restricts root radial expansion and modifies the penetration force of metal probes and plant roots. On the basis of the new results it is tentatively concluded that soil tensile failure can facilitate penetration by roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182016
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  • 3
    Electronic Resource
    Electronic Resource
    Behaviour of roots in cracks between soil peds (1983)
    Springer
    Plant and soil 74 (1983), S. 153-162 
    Details
    ISSN: 1573-5036
    Keywords: Cracks ; Crack orientation ; Elongation rate ; Pea ; Penetration ; Penetrometer ; Rape ; Roots ; Safflower ; Soil strength ; Soil structure ; Undisturbed soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experimental methods are described for observing the behaviour of roots growing over the surfaces of undisturbed soil clods and for roots growing along narrow cracks between two clods. Seminal roots of pea, rape and safflower were compared for a range of soil strengths and angles of inclination of the clod surfaces. For all three plant species, the ability of the roots to penetrate ped surfaces decreased with increasing soil strength and increasing angle of the surface relative to the horizontal. However, there was considerable variability of behaviour between roots. Roots were able to elongate more rapidly in cracks narrower than the root diameter than through undisturbed clods without cracks, provided that the crack was not orientated at an oblique angle to the preferred geotropic growth direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02143606
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