Effect of Strength, Tilth and Heterogeneity of the Soil Surface on Radicle‐entry of Surface‐sown Seeds

Campbell, Malcolm; Swain, F. G.

doi:10.1111/j.1365-2494.1973.tb00718.x

Cited by 27 publications

(16 citation statements)

References 15 publications

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“…Gerard (1965) showed that exchangeable cations influence soil strength in some soils; however in the Wycanna soils cations cannot be the cause as values are similar for different grazing pressures ( Table 2). The soil surface strengths measured are similar to those quoted by Campbell and Swain (1973), who found that the radicle of some legume species (lucerne and sub-clover) had difficulty penetrating soils ofthis strength. The existence of significant differences in soil strength is interpreted as a possible mechanism controlling species recruitment patterns.…”

Section: Resultssupporting

confidence: 59%

“…Plant population dynamics of the woodland are viewed as an interaction between changes caused by spatial interference between individual plants and population changes caused by fluctuations in or permanent changes to the resource base (Walker et al 1984), A general mathematical model of woodland dynamics has been proposed which involves six basic population processes; phenology, reproduction, recruitment, regeneration, growth and mortality (Walker et al 1984), Surface soil conditions are known to affect the processes associated with plant recruitment, for example, seedling emergence (Bennett et al 1964) and radicle penetration (Campbell & Swain 1973). Woody plant invasions in some parts of southern Africa have been associated with surface soil seals which form in heavily grazed woodlands (Kelly & Walker 1976).…”

Section: Introductionmentioning

confidence: 99%

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Recovery of some surface soil properties of ecological interest after sheep grazing in a semi‐arid woodland

Braunack

Walker

1985

Australian Journal of Ecology

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Solodic soils within a semi-arid poplar box (Eucalyptus populnea) woodland at Wycatvia, in southern Queenslatid, have been subjected to impacts frotn sheep atid cattle grazing for at least 100 years. The micromorphology of the surface of two soils, a gradational texture profile (Gn5.13, Paleustalf) and a duplex profile (Dbl.23, Paleustalf) showed that compaction had occurred. Recovery of the soil surfaces following retnoval of animal grazing was measured in tertns of porosity, presence of illuvial layers, surface soil strength, some chemical properties and water infiltration rates. The grazing impact was greatest on the Gn3.I3 soil and visttal signs ofthe grazing itnpact were still eviderit 16 years following sheep removal. Reduced soil organic matter atid increased surface soil hardtxess as a result of grazing, rather than surface crusting or changes In water mliliration rates are suggested as the mechanisms controlling the observed iticreases in woody plant populations in these semi-arid woodlatids.

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Section: Resultssupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Recovery of some surface soil properties of ecological interest after sheep grazing in a semi‐arid woodland

Braunack

Walker

1985

Australian Journal of Ecology

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Section: Discussionmentioning

confidence: 99%

“…Radicle entry is now widely recognized by agrostologists as an important stage in pasture establishment and difficulties in this regard have been encountered as a result of surface sowing of seeds of both legumes and grasses (McWilliam & Dowling 1970;Campbell & Swain 1973b;McKeon 1978). In grasses the reported devices include coleorhizal hairs (Campbell & Swain 1973b), epiblast hairs (Low 1966) and rigid awns with barbs (Smith 1968). If the radicle does not penetrate the soil quickly then both it and, ultimately, the seedling becomes desiccated (McWilliam, Clements & Dowling 1968) and such mortality can seriously limit the success of surface sowing (Campbell 1968;Cambell & Swain 1973a).…”

Section: Discussionmentioning

confidence: 99%

The Effects of Morphology, Orientation and Position of Grass Diaspores on Seedling Survival

Peart¹

1984

The Journal of Ecology

141

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. A ustralia SUMMARY (1) The orientation and position of 2193 germinating diaspores of eleven species of grasses were recorded as a result of observations in an open Eucalyptus forest over a period of 5 years. During three of these years further data were collected on the life histories of 1269 seedlings of nine of these species.(2) Amongst the species observed three gross structural forms of diaspore (activelyawned, passively-awned, and unawned) were recognized; each represented a distinct strategy for the recruitment of seedling populations.(3) While only sixteen seedlings of the actively-awned species Dichelachne micrantha and Themeda australis were observed in the area, all germinated from diaspores buried beneath the soil surface and only in situations where the soil was not surface crusting. These observations support the view that movements of the active awn propel the diaspore into cracks in the soil surface.(4) Seedlings of passively-awned species arose either from diaspores that were found in a standing orientation with their callused ends anchored in the soil or from diaspores that lay unanchored and almost horizontal on the soil surface. Germinating unawned diaspores were either lying on the surface or buried.(5) Anchorage of a diaspore is necessary for seedling survival. Spreading passive awns serve to rotate a falling diaspore into a position that increases its chances of landing in a standing orientation with the embedded antrosely-bristled callus providing the necessary anchorage.(6) Unawned diaspores achieve anchorages as a result of passive burial and it is postulated that dormancy delays the germination of many of these until effective burial is achieved.(7) Following a forest fire, a three-fold increase in the density of grass seedlings was recorded and the relative abundance of seedlings from unappendaged diaspores rose dramatically.(8) Since the morphology of appendaged diaspores promotes their germination on or near the soil surface, many such diaspores are destroyed by fire. In contrast, burial of unappendaged diaspores not only achieves anchorage but protects the seed from the extreme temperatures generated in a fire. Moreover, it is suggested that fire may release many of these seeds from dormancy.

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“…The high strength of uncultivated soils has been implicated in cases of poor plant establishment from surface sowing (Campbell and Swain, 1973). Soil strength, which increases upon drying after germinating rains, can prevent roots entering the soil surface.…”

Section: Introductionmentioning

confidence: 99%

Soil macrostructure and root growth of establishing seedlings

Cornish

1993

Plant Soil

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The importance of macrostructure to root growth of ryegrass (L. perenne) seedlings sown on the soil surface was studied in two soils in which the macrostructure had resulted mainly from root growth and macro-faunal activity. Sets of paired soil cores were used, one of each pair undisturbed and the other ground and repacked to the field bulk density.Undisturbed and repacked soils were first compared at equal water potentials in the range -1 . 9 to -3 0 0 kPa. At equal water potential, the undisturbed soil always had the greater strength (penetration resistance), and root growth was always greater in the repacked soil with no macrostructure than it was in the soil with macrostructure intact. At equal high strength (low water potentials) it appeared that root growth was better when soils were structured. When strength was low (high water potentials), root growth was better in the unstructured soil.Soils were then compared during drying cycles over 21 days. The average rate at which roots grew to a depth of 60 mm, and also the final percentage of plants with a root reaching 60 mm depth, was greatest in repacked soils without macrostructure. The species of vegetation growing in the soil before the experiment affected root growth in undisturbed soil; growth was slower where annual grasses and white clover had grown compared with soil which had supported a perennial grass.It appears that relatively few roots locate and grow in the macrostructure. Other roots grow in the matrix, if it is soft enough to be deformed by roots. Roots in the matrix of a structured soil grow more slowly than roots in structureless soil of equal bulk density and water potential. The development of macrostructure in an otherwise structureless soil, of the type studied, is of no advantage to most roots. However, once a macrostructure has developed, the few roots locating suitable macropores are able to grow at low water potential when soil strength is high. The importance of macrostructure to establishing seedlings in the field lies in rapid penetration of at least a few roots to a depth that escapes surface drying during seasonal drought.

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Effect of Strength, Tilth and Heterogeneity of the Soil Surface on Radicle‐entry of Surface‐sown Seeds

Cited by 27 publications

References 15 publications

Recovery of some surface soil properties of ecological interest after sheep grazing in a semi‐arid woodland

Recovery of some surface soil properties of ecological interest after sheep grazing in a semi‐arid woodland

The Effects of Morphology, Orientation and Position of Grass Diaspores on Seedling Survival

Soil macrostructure and root growth of establishing seedlings

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