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  • Aporrectodea rosea  (3)
  • Gossypium hirsutum  (3)
  • Springer  (6)
  • 2005-2009
  • 1985-1989  (6)
Collection
Keywords
Publisher
  • Springer  (6)
Years
  • 2005-2009
  • 1985-1989  (6)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Axial pressures generated by the earthworm Aporrectodea rosea (1988)
    Springer
    Biology and fertility of soils 5 (1988), S. 323-327 
    Details
    ISSN: 1432-0789
    Keywords: Earthworm ; Aporrectodea rosea ; Axial pressure ; Tunnelling ; Burrowing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The axial forces generated by the earthworm Aporrectodea rosea were measured by directing the earthworm to tunnel into soil discs mounted on an electronic balance connected to a datalogger. The area over which the force acted was estimated from the size of the hole created by the tunnelling. The maximum force recorded by an individual worm was 0.760 N and the mean maximum value was 0.465 N. The maximum pressures recorded was 116.5 kPa, while the mean maximum pressure was 72.8 kPa. These axial pressures are approximately one-tenth of the maximum axial pressure recorded for plant roots. The statistical distribution of activity as the worms tunnelled through the soil discs was analysed. Pressures recorded were well in excess of physiologically measured pressures and the generation of forces within muscles to achieve these pressures was calculated by some assumptions. It was estimated that there is a maximum tension in the circular muscles of 0.15 N per segment of the worm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262140
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  • 2
    Electronic Resource
    Electronic Resource
    Radial pressures generated by the earthworm Aporrectodea rosea (1988)
    Springer
    Biology and fertility of soils 5 (1988), S. 328-332 
    Details
    ISSN: 1432-0789
    Keywords: Earthworm ; Aporrectodea rosea ; Radial Pressure ; Tunnelling ; Indirect tension test ; Maximum force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The radial pressures generated by the earthworm Aporrectodea rosea were measured in a study of the conditions under which the worms were able to crack soil discs into which they were encouraged to tunnel. The tensile strength of replicate discs was determined by indirect tension tests and by expansion of rubber membranes in soil discs. Simple engineering theory was used to relate the stress required to fracture a disc with the applied internal stress. Mean values for the radial stress applied by the earthworms in tunnelling through the discs was 230 kPa. With some assumptions about the distribution of muscles across the worm diameter, it was estimated that the mean maximum force generated by all the longitudinal muscles in any segment was 3.2 N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262141
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  • 3
    Electronic Resource
    Electronic Resource
    Physical properties of casts of the earthworm Aporrectodea rosea (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 152-157 
    Details
    ISSN: 1432-0789
    Keywords: Earthworm Casts ; “Modexi” ; Shape ; Tensile strength ; Pressure ; Aporrectodea rosea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Some physical properties of casts of the earthworm Aporrectodea rosea were examined and compared with the properties of aggregates from the bulk soil. Cast shape was quantified by three ratio methods and two mathematical spectra methods, using data obtained by two-dimensional scanning. Shapes were compared with previously published descriptions of “modexi”. The tensile strength of dry casts was measured by the indirect tension method and was found to be approximately 2.5 times greater than that of dried aggregates of similar size. Tensile strengths are used to predict that beds of casts are less compactable than beds of aggregates. From relationships between soil water content, matric potential and undrained shear strength of fresh earthworm casts, the mean pressure applied to soil as it is remoulded by passing through the earthworm gut is estimated to be 259 Pa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257651
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  • 4
    Electronic Resource
    Electronic Resource
    Penetration of soil aggregates of finite size (1986)
    Springer
    Plant and soil 94 (1986), S. 59-85 
    Details
    ISSN: 1573-5036
    Keywords: Cohesion ; Gossypium hirsutum ; Helianthus annuus ; Penetrometer resistance ; Pisum sativum ; Plastic failure ; Radial stress ; Root diameter ; Root growth pressure ; Soil aggregates ; Tangential stress ; Tensile stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The axial force required for penetration of soil aggregates by roots of pea (Pisum sativum cv. Greenfeast), cotton (Gossypium hirsutum cv. Sicot 3) and sunflower (Helianthus annuus cv. Hysun) seedlings was measured. Effects of aggregate size and strength on root penetration behaviour were investigated. Maximum axial root growth pressure (P x ) was estimated from the maximum axial root growth force (F max) and mean root diameter. F max, time (T max) to attainF max, andP x all increased with increase in size and strength of aggregates. A significant interactive effect of size and strength of aggregate on root diameter was observed.F max,T max and root diameter were significantly different for different plant species. Maximum penetrometer pressure (P′) was compared with the axial pressures generated during root penetration. The penetrometer probe was found to overestimate the root growth pressure by a factor of 1.8 to 3.8.P x /P′ decreased with increase in size and strength of aggregates. A theory was developed to estimate radial and tangential stresses adjacent to the soil-root interface assuming cylindrical deformation by the root in aggregates of finite size. The stresses were calculated using shear cohesion values, estimated from tensile strength measurements, and with an assumed value of soil internal friction. Radial and tangential stresses adjacent to the root axis increased with increase in dimensionless aggregate radius and aggregate strength. Tensile stress adjacent to the root axis is predicted to result in plastic failure of finite sized aggregates during root penetration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02380590
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  • 5
    Electronic Resource
    Electronic Resource
    Role of root hairs in phosphorus depletion from a macrostructured soil (1988)
    Springer
    Plant and soil 107 (1988), S. 11-18 
    Details
    ISSN: 1573-5036
    Keywords: autoradiography ; Brassica napus ; Gossypium hirsutum ; macrostructured soil ; phosphorus depletion ; rhizosphere ; root hair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One rape (Brassica napus cv. Wesroona) plant and four cotton (Gossypium hirsutum cv. Sicot 3) plants were grown in plastic cells containing soil labelled with 407 kBq of33P g−1 soil. After 5–8 days of growth, the33P depletion zones of all plants were autoradiographed and33P uptake by plants was measured. The autoradiographs were scanned with a microdensitometer and the optical densities at several places within the33P depletion zones of roots were obtained. The volume of soil explored by root hairs was estimated from measurements of root diameters and lengths of roots and root hairs. About half of the total33P depleted by cotion roots came from outside the root hair cylinder whereas most of33P taken up by rape was from within the root hair cylinder. Plants grown in a macrostructured soil may have roots growing in voids, within aggregates or on the surfaces of aggregates. The results of this study demonstrate that root hairs have a strong influence on the accessibility of phosphorus to roots in such a soil, and thus on the phosphorus nutrition of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02371538
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  • 6
    Electronic Resource
    Electronic Resource
    Maximum axial and radial growth pressures of plant roots (1986)
    Springer
    Plant and soil 95 (1986), S. 315-326 
    Details
    ISSN: 1573-5036
    Keywords: Axial growth pressure ; Gossypium hirsutum ; Helianthus annuus ; Pisum sativum ; Radial growth pressure ; Root diameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The axial root growth force exerted by seedlings of pea (Pisum sativum cv. Greenfeast), cotton (Gossypium hirsutum cv. Sicot 3) and sunflower (Helianthus annuus cv. Hysun) was measured. Effects of different seedling age and different batches of seeds on axial root growth pressure were investigated. Mean values of the maximum axial root growth pressure (Pa) estimated from the maximum axial root growth force (Fmax) and root diameter were 497, 289, and 238 kPa respectively for pea, cotton and sunflower seedlings of same size. Pa and Fmax were significantly influenced by seedling age and for pea seedlings of same age they varied with the seed batch. A new technique was developed for estimating radial root growth pressure and was tested on pea seedlings. Each pea root was confined both in the axial and radial directions in a cylindrical chalk sample at a constant water potential. The roots exerted radial stress which caused tensile failure in a proportion of the chalks. The measurement of tensile strength of duplicate chalks enabled estimation of the maximum radial pressures exerted by the roots. The maximum axial and radial root growth pressures were of comparable magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374612
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