Patterns of seed softening and seedling emergence of nineteen annual medics during three years after a single seed crop in southern Queensland

1997 ◽  
Vol 37 (7) ◽  
pp. 767 ◽  
Author(s):  
D. L. Lloyd ◽  
G. B. Taylor ◽  
B. Johnson ◽  
K. C. Teasdale
Keyword(s):  
Seedling Emergence ◽  
Soil Surface ◽  
Farming Systems ◽  
The Other ◽  
Research Station ◽  
Hard Seed ◽  
Diurnal Cycles ◽  
Wide Range ◽  
Burr Medic ◽  
Annual Medics

Summary. To produce seed to determine the rates of seed softening of annual medics in the subtropics, 8 lines of barrel medic (Medicago truncatula), 3 lines of burr medic (M. polymorpha), 4 lines of snail medic (M. scutellata), and 1 line of each of button medic (M. orbicularis), strand medic (M. littoralis) and gama medic (M. rugosa) were grown at Warra in southern inland Queensland, in 1993. Seed of a fourth line of burr medic, a naturalised line, was harvested from Hermitage Research Station at that time. Pods were placed on the soil surface and buried at a depth of 7 cm, both in flywire envelopes and as free pods. Residual hard seed numbers were determined each year for 3 years from the envelopes, and seedlings were counted and removed from the free pods after each germination event. Patterns of softening of seeds from the same seed populations were also determined after placing them in a laboratory oven with a diurnal temperature fluctuation of 60/15° C for periods of 16, 40 and 64 weeks followed, after each time period, by 4 diurnal cycles of 35/10°C. More than 90% of the original seeds were hard. Seed softening at the soil surface ranged from 26% after 3 years in button medic to almost complete softening in the gama medic after only 2 years. Burial had little effect on the rate of softening of the button medic but about halved the rate of softening of the other lines. The barrel medics were vulnerable to losses of large numbers of seedlings which softened and germinated in January–February and the snail medics from seedlings emerging in August–December. The proportion of soft seeds recovered as seedlings in the buried compared with the surface pods was higher in the larger-seeded medics, snail and gama, and lower in the other, smaller-seeded medics. Laboratory techniques effectively ranked the medic lines for their rate of seed softening in the field and provided some insight into their seasonal patterns of seed softening. A wide range of seed softening patterns is available for fitting the requirements of various farming systems. The most appropriate pattern of softening will depend on the variability of medic seed production between years and the need for self regeneration of the medic after a cereal crop.

Effect of Environmental Factors on Germination and Emergence of Shortawn Foxtail (Alopecurus aequalis)

Weed Science ◽  
2017 ◽  
Vol 66 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Ning Zhao ◽  
Qi Li ◽  
Wenlei Guo ◽  
Lele Zhang ◽  
Lu’an Ge ◽  
...  
Keyword(s):  
Seed Germination ◽  
Osmotic Potential ◽  
Control Strategies ◽  
Abiotic Factors ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Burial Depth ◽  
Effective Measure ◽  
Wide Range

Shortawn foxtail is an invasive grass weed infesting winter wheat and canola production in China. A better understanding of the germination ecology of shortawn foxtail would help to develop better control strategies for this weed. Experiments were conducted under laboratory conditions to evaluate the effects of various abiotic factors, including temperature, light, pH, osmotic stress, salt concentration, and planting depth, on seed germination and seedling emergence of shortawn foxtail. The results showed that the seed germination rate was greater than 90% over a wide range of constant (5 to 25C) and alternating (15/5 to 35/25C) temperatures. Maximum germination occurred at 20C or 25/15C, and no germination occurred at 35C. Light did not appear to have any effect on seed germination. Shortawn foxtail germination was 27% to 99% over a pH range of 4 to 10, and higher germination was obtained at alkaline pH values ranging from 7 to 10. Seed germination was sensitive to osmotic potential and completely inhibited at an osmotic potential of −0.6 MPa, but it was tolerant to salinity: germination even occurred at 200 mM NaCl (5%). Seedling emergence was highest (98%) when seeds were placed on the soil surface but declined with the increasing burial depth. No seedlings emerged when seeds were buried 6-cm deep. Deep tillage could be an effective measure to limit seed germination from increased burial depth. The results of this study will lead to a better understanding of the requirements for shortawn foxtail germination and emergence and will provide information that could contribute to its control.

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.

Effects of Environmental Factors on Seed Germination and Emergence of Japanese Brome (Bromus japonicus)

Weed Science ◽  
2015 ◽  
Vol 63 (3) ◽  
pp. 641-646 ◽  
Author(s):  
Qi Li ◽  
Jinni Tan ◽  
Wei Li ◽  
Guohui Yuan ◽  
Long Du ◽  
...  
Keyword(s):  
Salt Stress ◽  
Osmotic Stress ◽  
Control Strategies ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Farming Systems ◽  
Effect Of Temperature ◽  
Burial Depth ◽  
Ph Values ◽  
Winter Annual

Japanese brome is a winter annual weed commonly found in wheat fields in China. Laboratory and greenhouse experiments were carried out to determine the effect of temperature, light, pH, osmotic stress, salt stress, and burial depth on the germination and emergence of Japanese brome. Germination was greater than 98% under a wide temperature range of 5 to 30 C and onset of germination was shortened as temperature increased. Light was not required for germination to occur and pH values from 5 to 10 had insignificant effect on germination. Germination was reduced by osmotic stress or salt stress and no germination occurred at −1.3 MPa or 360 mM, suggesting that Japanese brome seed was quite tolerant to osmotic potential and salinity. Seedling emergence was greatest (98%) when seeds were placed on the soil surface but decreased with increasing of burial depth. Only 7% of seedlings emerged at a depth of 5 cm. The results of this study have contributed to our understanding of the germination and emergence of Japanese brome and should enhance our ability to develop better control strategies in wheat farming systems of the Huang-Huai-Hai Plain of China.

scholarly journals Germination Ecology of Two Troublesome Weeds of Arid Chickpea: Euphorbia dracunculoides and Astragalus Species

2019 ◽  
Vol 37 ◽  
Author(s):  
R.M. IKRAM ◽  
A. TANVEER ◽  
H.H. ALI ◽  
M.E. SAFDAR ◽  
M.M. JAVAID ◽  
...  
Keyword(s):  
Seed Germination ◽  
Seedling Emergence ◽  
Chloride Concentration ◽  
Ecological Factors ◽  
Cropping System ◽  
Soil Surface ◽  
Growth Patterns ◽  
Burial Depth ◽  
Germination Ecology ◽  
Wide Range

ABSTRACT: The species Euphorbia dracunculoides and Astragalus are problematic weeds of arid chickpea in the chickpea mono-cropping system in Pakistan. The influence of various ecological factors on germination and seedling emergence characteristics of these weeds was determined under laboratory conditions. The results suggested that seed germination of both species was 50% at 15 oC under light conditions, and germination decreased when the temperature was increased. The increase in drought stress from 2.5 to 15% significantly decreased germination of E. dracunculoides and Astragalus spp. Both species failed to germinate at the osmotic potential of -3.02 MPa. The increase in field capacity from 25 to 100% increased emergence percentage and emergence index of both weeds. A pH range of 6 to 9 did not influence seed germination of both species and they were able to germinate at a wide range of pH conditions. Both weeds were very sensitive to salinity; however, a few seeds (10%) of Astragalusspp. germinated even at a 150 mM sodium chloride concentration. To check the effect of burial depth, seeds were placed in pots under seeding depths of 0 to 6 cm at an interval of 1 cm, respectively. Maximum emergence was attained at the soil surface and emergence declined with increasing depths. Seedling emergence of E. dracunculoides was higher than that of Astragalusspp. at all burial depths. Studies on germination ecology of these two weeds will offer insights into their behavior under different environmental conditions. Their germination responses and growth patterns under different ecological factors will help us to design an efficient management strategy to control these two troublesome weeds.

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.

No-tillage planters for heavy-textured Alfisols in the semi-arid tropics of Australia

1996 ◽  
Vol 36 (8) ◽  
pp. 957
Author(s):  
NS Gould ◽  
DCI Peake ◽  
NP Dalgliesh
Keyword(s):  
Seedling Emergence ◽  
The Other ◽  
Soil Conditions ◽  
Research Station ◽  
No Tillage ◽  
Wet Season ◽  
Seedling Mortality ◽  
Moisture Regimes ◽  
Dry Conditions ◽  
Effective Depth

This paper provides key information on 4 no-tillage planters to facilitate adoption by fanners in northern Australia. Four commercial planters (Buffalo All-Flex Convertible slot planter, Buffalo All-Flex Compact slot planter, John Deere Max-Emerge planter and Mason Spring Release (SR) Integral planter) of contrasting design were tested in various configurations under 5 different moisture regimes during drying of a heavy-textured Alfisol at Katherine Research Station, Northern Territory, Australia (14�20'S, 132�20�E, 108 m altitude) at the end of the 1982-83 wet season. Significant differences in emergence were measured between planters and between configurations under most moisture regimes. Seedling emergence was greatest in Buffalo-Compact planter treatments, less for Buffalo-Convertible and Mason SR Integral treatments and lowest for John Deere Max-Emerge treatments. The Buffalo planters, each with an effective trash cutting coulter and narrow tine slot opener, produced consistently better results under all moisture regimes than the other 2 planters. The Mason SR Integral, with its wide tine opener, created a high incidence of clods which restricted emergence and led to increased occurrence of unimbibed seeds. Generally, for the 3 tine opener planters, the looser the soil in the furrow, the poorer the emergence. The John Deere Max-Emerge double-disc opener, whilst performing well under moist conditions, generally performed poorly when soil conditions were dry. This planter was on most occasions unable to maintain effective depth control under excessively wet or dry conditions, resulting in lower in-furrow soil moisture and significantly poorer and slower emergence than occurred with the other planters. In-furrow seed-firming presswheels, applying a contact pressure of approximately 4-5 kg/cm of presswheel tyre width, ensured better seed-soil contact and higher emergence levels than twin-inclined overfurrow presswheels. The over-furrow presswheels fitted to the John Deere Max-Emerge planter were often unable to close the slot effectively, resulting in the creation of voids and caps with resultant high seedling mortality.

Effect of the environment in which seeds are grown and softened on the incidence of autumn seed softening in two species of annual medics

1996 ◽  
Vol 47 (1) ◽  
pp. 141 ◽  
Author(s):  
GB Taylor
Keyword(s):  
Environmental Conditions ◽  
Selection Criterion ◽  
Temperature Fluctuations ◽  
Term Treatment ◽  
First Year ◽  
Short Term Treatment ◽  
Diurnal Cycles ◽  
Wide Range ◽  
Improvement Programs ◽  
Annual Medics

The incidence of autumn seed softening, which is believed to offer some protection against false breaks of season, was investigated under a range of environmental conditions in three medic cultivars over three years of softening. Newly ripened pods of burr medic (Medicago polymorpha L.) cvv. Serena and Santiago, and barrel medic (M. truncatula Gaertn.) cv. Cyprus, that were grown at three sites were transferred to four seed softening sites in December. Their progress of seed softening was determined in March, April and June. The seed softening process was also studied in a range of laboratory treatments. Seed growing environments were more important than seed softening environments in determining rates of seed softening in all cultivars. However, the distribution of softening between summer and autumn was generally consistent between the growing and softening environments. More than half the annual softening of Serena and Santiago seeds occurred between the first week of March and June in each of the first three years. A smaller proportion of Cyprus seeds softened between March and June in the first and third years than was the case with the other cultivars. In the first year of softening most of the Serena and Santiago seeds that went on to soften between March and June were already present as latent soft seeds (impermeable seeds that soften rapidly once subjected to appropriate temperature fluctuations) in March, as determined by short-term treatment at 35/10�C. There were fewer latent soft seeds present at this time in later years that responded to this same treatment, suggesting that the longer-term hard seeds had other temperature requirements for the final stage of seed softening. High correlations (r2 = 0.90) were obtained between percent seed softening of the three cultivars in the field in the first year and after laboratory treatment with diurnal temperature fluctuations of 60/15�C for 16 weeks, followed by four diurnal cycles of 35/10�C. Autumn seed softening is sufficiently consistent under a wide range of environmental conditions to be a worthwhile selection criterion in medic improvement programs.

Threelobe Morningglory (Ipomoea triloba) Germination and Response to Herbicides

Weed Science ◽  
2012 ◽  
Vol 60 (2) ◽  
pp. 199-204 ◽  
Author(s):  
Bhagirath Singh Chauhan ◽  
Seth Bernard Abugho
Keyword(s):  
Weed Management ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Soil Surface ◽  
The Philippines ◽  
Integrated Weed Management ◽  
Burial Depth ◽  
Early Application ◽  
Hard Seed ◽  
Ipomoea Triloba

Experiments were conducted in the laboratory and screenhouse to determine the effects of scarification; alternating day/night temperatures; light, salt, and water stress; seed burial depth; and rice residue on seed germination and seedling emergence of threelobe morningglory, and to evaluate the response of this weed to commonly available POST herbicides in the Philippines. Germination was stimulated by seed scarification, suggesting that inhibition of germination in this species is mainly due to the hard seed coat. Germination of the scarified seeds was not influenced by the tested temperatures (alternating day/night temperatures of 25/15, 30/20, and 35/25 C) and light. The concentrations of sodium chloride, ranging from 0 to 250 mM, did not influence germination of the scarified seeds of threelobe morningglory. The osmotic potential required for 50% inhibition of maximum germination was −0.35 MPa, although some seeds germinated at −0.6 MPa. Seedling emergence was greatest for the seeds placed on the soil surface (96%), and emergence declined with increased burial depth in soil. The burial depth required for 50% inhibition of maximum emergence was 2.8 cm. No seedlings emerged from a burial depth of 6 cm or greater. Residues of up to 6 Mg ha−1on the soil surface did not influence seedling emergence of threelobe morningglory. The herbicide 2,4-D at 400 g ai ha−1provided excellent control of threelobe morningglory when applied at the four-leaf (100%) and six-leaf (97%) stages. However, at the eight-leaf stage, percent control was reduced to 67% and herbicide rate had to be increased twofold to achieve 95% control. The information gained from this study could contribute to developing components of integrated weed management strategies for threelobe morningglory. Soil inversion by tillage to bury weed seeds below their maximum depth of emergence and early application of an effective POST herbicide could serve as important tools for managing threelobe morningglory.

Weedy rice (Oryza sativa) II. Response of Weedy Rice to Seed Burial and Flooding Depth

Weed Science ◽  
2012 ◽  
Vol 60 (3) ◽  
pp. 385-388 ◽  
Author(s):  
Bhagirath Singh Chauhan
Keyword(s):  
Seedling Emergence ◽  
Soil Surface ◽  
Production Costs ◽  
The Other ◽  
Weedy Rice ◽  
Burial Depth ◽  
Rice Accession ◽  
Seed Burial ◽  
Seedling Biomass ◽  
Flooding Depth

Weedy rice is a serious problem of cultivated rice in most of the rice-growing areas in Asia, causing increased production costs and yield losses in rice. A study was conducted to determine the response of weedy rice accessions from India (IWR), Malaysia (MWR), Thailand (TWR), and Vietnam (VWR) to seed burial and flooding depths. The greatest emergence for each weedy rice accession (97% for IWR, 82% for MWR, 97% for TWR, and 94% for VWR) was observed in seeds placed on the soil surface. Seedling emergence decreased with increase in burial depth. For the IWR accession, 0.5% of the seedlings emerged from 8-cm depth, whereas for the other three weedy rice accessions, no seedlings emerged from this depth. When seeds were sown on the soil surface, flooding depth ranging from 0 to 8 cm had no or very little effect on seedling emergence of different weedy rice accessions. On the other hand, flooding decreased seedling emergence in all weedy rice accessions when seeds were sown at 1 cm deep into the soil. Compared with seedling emergence, flooding had a more pronounced effect on seedling biomass for all weedy rice accessions. A flooding depth of 2 cm reduced seedling biomass by an amount greater than 85% of each weedy rice accession. The results of this study suggest that emergence and growth of weedy rice could be suppressed by deep tillage that buries seeds below their maximum depth of emergence (i.e., > 8 cm for the accessions studied) and by flooding fields as early as possible. The information gained from this study may help design cultural management strategies for weedy rice in Asia.

Seed-germination ecology of glyphosate-resistant and glyphosate-susceptible biotypes of Echinochloa colona in Australia

2019 ◽  
Vol 70 (4) ◽  
pp. 367 ◽  
Author(s):  
Navneet Kaur Mutti ◽  
Gulshan Mahajan ◽  
Bhagirath Singh Chauhan
Keyword(s):  
Water Stress ◽  
Sodium Chloride ◽  
Seed Germination ◽  
Seedling Emergence ◽  
Chloride Concentration ◽  
Soil Surface ◽  
Burial Depth ◽  
Solution Ph ◽  
High Sodium ◽  
Wide Range

Echinochloa colona L. (Link) (awnless barnyard grass) is one of the top three most problematic weeds of summer crops in Australia. This weed has evolved resistance to glyphosate. A study was conducted to evaluate the effect of environmental factors on the germination and seedling emergence of a glyphosate-resistant (GR) and a glyphosate-susceptible (GS) biotype of E. colona. The two biotypes had similar germination and emergence responses to light and temperature conditions, water stress, solution pH, sorghum residue cover and seed burial depth. Light stimulated germination more than dark conditions, and seeds germinated at a wide range of alternating day/night temperatures, from 20°C/10°C to 35°C/25°C, whereas no seeds germinated at 15°C/5°C. These results suggest that E. colona can emerge in spring, summer and autumn in Queensland. The sodium chloride concentration required to inhibit 50% germination was greater for the GR biotype (209 mm) than the GS biotype (174 mm). Seed germination was not affected by pH in the range 4–10. Water stress reduced germination by 50% at an osmotic potential of –0.44 MPa. In a shade-house study, retention of sorghum residue cover on the soil surface reduced the seedling emergence of E. colona. Emergence was 70% in the absence of crop residue, whereas a residue amount of 8 t ha–1 reduced emergence to 47%. Emergence was greatest for seeds placed on the soil surface and declined linearly with increasing burial depth; no seedlings emerged from 8 cm depth. The GR biotype had higher germination than the GS biotype under high sodium chloride concentrations; therefore, this biotype may be highly competitive with crops under highly saline conditions. Because germination was high on the soil surface and was stimulated by light, this weed will remain problematic under no-till farming systems in Australia.

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