Effect of burial on the softening of hard seeds of subterranean clover

1984 ◽  
Vol 35 (2) ◽  
pp. 201 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
The Other ◽  
Soil Tillage ◽  
Microbial Decomposition ◽  
Buried Seeds ◽  
Hard Seeds ◽  
Depth Of Burial

Burrs of eight varieties of subterranean clover (Trifolium subterraneum L.), which had experienced one summer at the soil surface, were placed on the soil surface and at depths of 2, 6 and 10 cm in the soil. The numbers of residual hard seeds were determined after 1, 2 and 3 years. The effects of laboratory treatment at a diurnally fluctuating temperature of 60/15�C on the softening of buried seeds and of seeds stored in the laboratory for 1 and 3 years were determined. Rate of seed softening in all varieties decreased with increasing depth of burial, apparently because the soil insulated the seeds from high soil surface temperatures. Few seeds of the varieties Northam and Geraldton softened during 3 years of burial at 6 or 10 cm; while, at the other extreme, few seeds of Yarloop survived 3 years at any depth. Some evidence was found for microbial decomposition of hard seeds in the field. Seeds softened more readily at 60/15�C (in the laboratory) as the preceding periods of either laboratory storage or field burial increased. Such storage or burial experiences have a preconditioning effect on hard seeds, making them more amenable to softening once they are subjected to wide diurnal temperature fluctuations. The results indicate that soil tillage associated with cropping should build up a useful soil seed reserve of the harder seeded varieties.

The influence of the growing season and the following dry season on the hardseeedness of subterranean clover in different environments

1965 ◽  
Vol 16 (3) ◽  
pp. 277 ◽  
Author(s):  
BN Quinlivan
Keyword(s):  
Surface Temperature ◽  
Critical Factor ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Growing Season ◽  
Growing Period ◽  
Hard Seeds ◽  
Soil Surface Temperature

The length of the growing period in the spring months appears to be a critical factor in the development of hardseededness in subterranean clover (Trifolium subterraneum L.). Environments with relatively long spring growing periods cause a higher proportion of hard seeds to form at field maturity, and increase the resistance which these hard seeds are capable of offering to the softening effects of the following summer environment. During the dry summer period the rate of softening of hard seeds is determined, not only by the previous growing season but also by the summer environment itself. Hot summer environments with wide soil surface temperature fluctuations are conducive to a relatively rapid rate of softening. Grazing or removal of the dry topgrowth from a pasture during the summer increases the daily soil surface temperature fluctuations, and results in the hard seeds softening at an increased rate. Differences in the overall environment manifest themselves in terms of site and seasonal variation in the proportion of hard seeds which survive beyond the opening of the following growing season. The scope for variation is wide, and this has agronomic significance from the aspect of long-term persistence of the species.

Effect of depth of burial on the longevity of hard seeds of subterranean clover and annual medics

1988 ◽  
Vol 28 (1) ◽  
pp. 77 ◽  
Author(s):  
GB Taylor ◽  
MA Ewing
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Barrel Medic ◽  
Hard Seeds ◽  
Burr Medic ◽  
Seed Reserves ◽  
Annual Medics ◽  
Depth Of Burial ◽  
Tillage Operations

Burrs of 3 cultivars of subterranean clover (Trifolium subterraneum) and 1 cultivar each of burr medic (Medicago polymorpha) and barrel medic (M. truncatula), which had experienced 1 summer at the soil surface, were placed on the soil surface and at depths of 2, 6 and 10 cm in the soil. The numbers of residual hard seeds were determined each year for up to 4 years. There was a marked reduction in the rate of seed softening in all 3 clover cultivars with increasing depth of burial. Whereas <20% of the seeds of the hardest seeded clover cultivar, Nungarin, survived 3 years at the soil surface, there was no significant decline in seed numbers during 4 years of burial at 10 cm. Even with cv. Geraldton, in which only 5% of seeds remained after 1 year of placement at the soil surface, 75% of seeds survived 4 years of burial at 10 cm. Hard seeds of both medic varieties were considerably more resilient than clover seeds at the soil surface, particularly during the first summer following seed set. However, burial had much less effect on their longevity, with no significant effect of burial to 2 cm in either medic, or of burial to 6 cm in the case of barrel medic. These results support earlier findings which showed that tillage operations associated with crop establishment which result in the burial of substantial proportions of subterranean clover seeds can lead to useful soil seed reserves. The much lesser effect of burial on seed softening of the medics, compared with subterranean clover, suggests that tillage operations will be less advantageous to medic persistence in leys.

Incidence and measurement of autumn seed softening within Medicago polymorpha L

1996 ◽  
Vol 47 (4) ◽  
pp. 575 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Soil Surface ◽  
Temperature Fluctuations ◽  
The Other ◽  
Laboratory Simulation ◽  
First Year ◽  
Medicago Polymorpha ◽  
Softening Behaviour ◽  
Hard Seeds ◽  
Total Seed

Softening of hard seeds during autumn rather than summer is a desirable characteristic for reducing seed losses in annual legumes from false breaks of season in Mediterranean environments. The incidence of this characteristic in Medicago polymorpha L. was determined in 34 lines grown at Toodyay, Western Australia, in 1993 and collected in December. Patterns of seed softening during summer and autumn 1993-94 were studied in pods placed on the soil surface in the field at Merredin, and in laboratory and glasshouse simulations at Perth. Summer seed softening was simulated in the laboratory by the removal of seeds from pods by hand, subjecting them to a diurnally fluctuating temperature of 60/15�C for 16 weeks, and testing their permeability. Residual hard seeds were subjected to 4 gradual diurnal temperature fluctuations of 35/10�C and re-tested for permeability as a measure of autumn seed softening. In the glasshouse study, pods were placed on the surface of soil in boxes, and emerged seedlings were counted after watering in March and June. Field softening in the first year ranged from 6.8 to 69.6%, but exceeded 40% in only 6 of the 34 lines. Proportions of total soft seeds present in the field in June that had softened after 1 March in the 34 lines were normally distributed, and ranged from 2.5 to 78.7%. The laboratory simulation markedly underestimated both autumn and total seed softening in 13 of the lines but effectively predicted field softening behaviour in the other 21 lines. The glasshouse technique overestimated the proportions of seeds softening in autumn in most lines and underestimated total softening in 12 of the 34 lines. A technique involving the use of a rain-out shelter is proposed for routine determination of the incidence of autumn seed softening in medic evaluation programs.

The action of temperature fluctuations on hard seeds of subterranean clover

1971 ◽  
Vol 11 (51) ◽  
pp. 440 ◽  
Author(s):  
MW Hagon
Keyword(s):  
No Reduction ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Specific Region ◽  
Daily Temperature ◽  
Laboratory Conditions ◽  
Hard Seeds ◽  
Cycle Lengths ◽  
Daily Temperature Fluctuations

Burrs of three cultivars of subterranean clover (Trifolium subterraneum) were placed in soil in a cold frame at Canberra so that they were subjected to daily temperature fluctuations of the order of 20-54�C. After three months and eight months the proportion of permeable seeds was significantly increased. Such seeds were conductive to water at one specific region of the testa-the strophiole. In a further experiment, under laboratory conditions, hard seeds were subjected to temperature fluctuations of 23-60�C with cycle lengths varying from 15 minutes to 1 hour. There was no reduction in the percentage of hard seeds except in two trials when that portion of each cycle at 60�C was greater than 45 minutes.

Effects of extended (4-12 years) burial on seed softening in subterranean clover and annual medics

1996 ◽  
Vol 36 (2) ◽  
pp. 145 ◽  
Author(s):  
GB Taylor ◽  
MA Ewing
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Razor Blade ◽  
Barrel Medic ◽  
Hard Seeds ◽  
Soil Temperatures ◽  
Burr Medic ◽  
Annual Medics ◽  
Softening Process

The effect of burial of seeds of 3 cultivars of subterranean clover (Trifolium subterraneum) and 1 cultivar each of burr medic (Medicago polymorpha) and barrel medic (M. truncatula) that had experienced 1 summer at the soil surface was continued from 4 to up to 12 years. Seeds were situated at 2, 6 and 10 cm depth, as well as at the soil surface. Numbers of residual seeds were determined after each sampling occasion, the timing of which was varied between cultivars and depths of burial according to the progress of seed softening. The marked reduction in the rate of seed softening in all 3 clover cultivars with increasing depth of burial established during the first 4 years of the experiment was maintained. After 12 years, 37% of the Nungarin clover seeds that had been buried at 10 cm were still present as hard seeds. All residual hard seeds germinated readily after nicking with a razor blade. Seeds of both medic cultivars, that were slower to soften than the clovers at the soil surface, continued to show little effect of burial at 2 cm, or of burial to 6 cm in the case of Cyprus barrel medic. Species differences in response to seed burial are explained in terms of the effects of soil temperatures on the 2-stage seed softening process. The absence of an effect of shallow burial on the softening of medic seeds appears to be attributable to a lower optimum temperature for the first stage of seed softening than is the case for subterranean clover. Unfavourable temperatures for the final stage of seed softening can result in the accumulation of latent soft seeds, particularly in subterranean clover. These latent soft seeds will soften during the first summer/autumn after their return to close to the soil surface as a consequence of tillage. Whereas increased seed longevity as a consequence of burial in crop years can be advantageous in terms of legume persistence, particularly of clover, it can also be distinctly disadvantageous when it comes to cultivar replacement.

The relationship between temperature fluctuations and the softening of hard seeds of some legume species

1966 ◽  
Vol 17 (5) ◽  
pp. 625 ◽  
Author(s):  
BJ Quinlivan
Keyword(s):  
Critical Factor ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Maximum Temperature ◽  
Hard Seeds ◽  
Maximum Temperatures ◽  
The Relationship ◽  
Fluctuating Temperatures ◽  
Main Factor

Hard seeds of subterranean clover (Trifolium subterraneum L.) of the Geraldton and Bacchus Marsh strains, and of West Australian blue lupin (Lupinus varius L.), were subjected to various daily fluctuating temperatures within the normal summer environmental range (15–75°C). The main factor determining the rate of softening of the hard seeds was the maxinlum temperature of the fluctuation. Provided the temperature changed by some 15°C , the amplitude of the fluctuation did not appear to be a critical factor. The softening of hard seeds of any particular species did not commence until the amplitude of the temperature fluctuation, or the maximum temperature, reached a certain level, which in turn varied with the species. Beyond this level the rate of softening increased with increasing fluctuations to a point where the rate became very rapid, and thereafter wider fluctuations or higher maximum temperatures did not give significant increases.

Hardseededness and the pattern of softening in Biserrula pelecinus L., Ornithopus compressus L., and Trifolium subterraneum L. seeds

1999 ◽  
Vol 50 (6) ◽  
pp. 1073 ◽  
Author(s):  
A. Loi ◽  
P. S. Cocks ◽  
J. G. Howieson ◽  
S. J. Carr
Keyword(s):  
Seed Bank ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Farming System ◽  
First Year ◽  
Ley Farming ◽  
Sufficient Variation ◽  
Depth Of Burial ◽  
Selection Of

Experiments measuring seed bank size, hardseededness, and seed softening of biserrula (Biserrula pelecinus L.) were conducted at Merredin and Perth in Western Australia. At Merredin, a mixture of 2 biserrula accessions was grazed, shallow cultivated, or left uncultivated and ungrazed. Seed bank size, seedling regeneration, and seed softening were measured over 2 years. At Perth, softening of biserrula, yellow serradella, and subterranean clover seeds grown at 2 sites (Binnu and Northam) was compared on the soil surface and after burial at 2 and 10 cm over a period of 2 years. Seed bank size of biserrula at Merredin ranged from 14000 to 17500 seeds/m2. Regeneration was greater in the second year (800–1700 seedlings/m2) than in the first year (40–600 seedlings/m2). In both years the shallow cultivated treatment recorded the highest number of seedlings. About 90% of biserrula and serradella seed remained hard after 2 years on the soil surface, compared with only about 10% of subterranean clover. Serradella softened more rapidly when buried 2 cm below the soil surface (8–12% hard) than it did on the soil surface (84–92% hard) (P<0.05). In contrast, the softening of subterranean clover decreased with increasing depth. Biserrula was intermediate, although it too softened most rapidly at 2 cm (78–95% hard compared with 82–97% on the surface) (P<0.05). Rate of seed softening in all species decreased with increasing depth of burial below 2 cm. Of the 4 accessions of biserrula, an accession from Greece (83% hard after 2 years exposure) was significantly softer than the other accessions. The results indicate that biserrula is very hardseeded, although there is sufficient variation in hardseededness for the selection of somewhat softer lines. Its pattern of softening suggests that biserrula may be successful in the ley farming system (crop/pasture rotations) of southern Australia.

The effect of constant and fluctuating temperatures on the permeability of the hard seeds of some legume species

1961 ◽  
Vol 12 (6) ◽  
pp. 1009 ◽  
Author(s):  
BJ Quinlivan
Keyword(s):  
Constant Temperature ◽  
Temperature Fluctuation ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Temperature Fluctuations ◽  
Lupinus Luteus ◽  
Maximum Effect ◽  
Rate Of Increase ◽  
Hard Seeds ◽  
Temperature Ranges

Hard seeds of Lupinus digitatus Forsk., Lupinus luteus L., Medicago tribuloides Desr., and Trifolium subterraneum L. (Mt. Barker, Dwalganup, and Geraldton strains) were subjected to constant temperatures of 60 and 140°F, and to fluctuating temperature ranges of 60–115°F, 60–140°, and 60–165°, for a period of 5 months. The temperature fluctuation treatments were set to follow patterns similar to those experienced on the soil surface during the summer months in the agricultural districts of Western Australia. Increased permeability, i.e. an increase in the percentage of seeds permeable to water, took place under all temperature conditions. The lowest increase occurred at a constant temperature of 60°F. A constant temperature of 140° gave a relatively higher increase. All three temperature fluctuation treatments increased the permeability as compared with the constant temperatures, with maximum effect at a range of 60-140°F. Increasing the range to 60–165° did not increase the permeability. With the exception of L. digitatus all species subjected to temperature fluctuations showed a rapid increase in permeability over the first 2 or 3 months. Beyond this point the rate of increase was very slow. The permeability or softening pattern followed by L. digitatus was almost the direct opposite to that of the other species. Of the three strains of T. subterraneum, Mt.. Barker showed the highest increase in permeability under temperature fluctuations and Geraldton the least.

Response of defoliated swards of subterranean clover and yellow serradella to superphosphate applications

1991 ◽  
Vol 31 (6) ◽  
pp. 777
Author(s):  
MDA Bolland
Keyword(s):  
Field Experiment ◽  
Sandy Soil ◽  
Dry Matter ◽  
Maximum Yield ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Herbage Yield ◽  
Ornithopus Compressus ◽  
The Relationship

The effect of superphosphate applications (0, 25, 50, 75, 100 and 125 kg P/ha to the soil surface) on the dry matter (DM) herbage production of dense swards of subterranean clover (Trifolium subterraneum cv. Junee) and yellow serradella (Ornithopus compressus cv. Tauro) was measured in a field experiment on deep, sandy soil in south-western Australia. The swards were defoliated with a reel mower at weekly intervals from 88 to 158 days after sowing, to a height of 2 cm for the first 9 cuts, 4 cm for the tenth cut and 5 cm for the eleventh cut. Yellow serradella was more productive than subterranean clover. Consequently, for the relationship between yield and the level of phosphorus (P) applied, yellow serradella supported larger maximum yields and required less P than subterranean clover, to produce the same DM herbage yield. Maximum yields of yellow serradella were 12-40% larger. To produce 70% of the maximum yield for yellow serradella at each harvest, yellow serradella required about 50% less P than subterranean clover. However, when yields were expressed as a percentage of the maximum yield measured for each species at each harvest, the relationship between yield and the level of P applied was similar for both species, and they had similar P requirements.

Effect of perennial pasture species on surface soil moisture and early growth and survival of subterranean clover (Trifolium subterraneum L.) seedlings

1997 ◽  
Vol 48 (5) ◽  
pp. 683 ◽  
Author(s):  
B. S. Dear ◽  
P. S. Cocks
Keyword(s):  
Mineral Soil ◽  
Subterranean Clover ◽  
Late Summer ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Annual Grass ◽  
Growth And Survival ◽  
Eastern Australia ◽  
Standing Dead ◽  
Clover Seed

Subterranean clover seedling numbers and growth in swards containing 1 of 5 perennial pasture species [phalaris (Phalaris aquatica) cv. Sirolan, cocksfoot (Dactylis glomerata) cv. Currie, lucerne (Medicago sativa) cv. Aquarius, wallaby grass (Danthonia richardsonii) cv. Taranna, and lovegrass (Eragrostis curvula) cv. Consol] were compared with those in typical annual pastures and pure clover swards in the wheatbelt of eastern Australia. Presence of a perennial species or the volunteer annual grass (Eragrostis cilianensis) increased the rate of drying of the soil surface (0–5 cm) after late February and May rain, compared with subterranean clover swards. Perennials differed in the rate they dried the soil surface, with the more summer-active lucerne and consul lovegrass drying the profile more rapidly than phalaris. The amount of water in the surface 5 cm, 6 days after the rainfall event on 27–28 February, was strongly negatively correlated (r = –0·75, P < 0·01) with the amount of green perennial biomass, but not related to standing dead material or surface residues. Where perennials were present, a smaller proportion (2–4%) of the clover seed pool produced seedlings in response to late summer rain, compared with pure clover swards (18%). A higher proportion of the seed pool produced seedlings (19–36%) following rain in late autumn but there was no difference between species. The more summer-active perennials (cocksfoot, danthonia, and lucerne) markedly depressed the survival of emerged clover seedlings following both germinations. Of the seedlings that emerged in early March, the proportion remaining by 29 March was 57% in phalaris, 21% in lucerne, 13% in danthonia, and 1% in cocksfoot, compared with a 78% increase in seedlings in pure subterranean clover swards. By 15 May, all perennials had <2 clover seedlings/m2 surviving, compared with 37 in the annual pasture and 964 plants/m2 in pure subterranean clover. Following the May germination, the highest proportion of emerged seedlings surviving until 29 May was in the phalaris swards (40%) and least in the cocksfoot and danthonia swards (2–4%). Presence of a perennial or annual grass decreased (P < 0·05) relative water content of clover seedlings on 15 March from 74% in pure clover swards, to 48% in annual pasture, 34% in phalaris, and 29% in lucerne swards. Clover seedlings growing in pure subterranean swards on 15 March (17 days after germinating rain) were 4 times larger than those in lucerne and twice as large as those in either phalaris or annual pasture. Seed size did not differ between treatments, but available mineral soil nitrogen was significantly higher (P < 0·001) in pure subterranean clover swards (32 mg N/g) compared with perennials (3–13 mg N/g). Strategies such as heavy grazing in late summer to reduce green biomass of the perennials or sowing the perennials at lower densities may reduce the adverse effects that perennials have on subterranean clover seedlings in these drier environments.

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