Germination ecology of six species of Eucalyptus in shrink–swell vertosols: moisture, seed depth and seed size limit seedling emergence

2017 ◽  
Vol 65 (1) ◽  
pp. 22 ◽  
Author(s):  
Lorena Ruiz Talonia ◽  
Nick Reid ◽  
Caroline L. Gross ◽  
R. D. B. Whalley
Keyword(s):  
Soil Moisture ◽  
Seed Size ◽  
Seedling Emergence ◽  
Seed Viability ◽  
Direct Seeding ◽  
Eucalyptus Species ◽  
Sowing Depth ◽  
South Wales ◽  
Dry Conditions ◽  
Moisture Conditions

We examined the potential of direct-seeding Eucalyptus species to revegetate the vertosol (‘cracking clay’) soils that characterise the floodplains of north-western New South Wales. We investigated the influence of sowing depth (0, 6, 12 and 20 mm) and three soil-moisture scenarios (dry, moist and flooded) on seedling emergence of seedlings of six species of Eucalyptus with a range of seed sizes (E. blakelyi, E. camaldulensis, E. melanophloia, E. melliodora, E. pilligaensis and E. populnea). We used cracking clay soil from the region in a glasshouse environment. Seedling emergence was low despite high seed viability and provision of optimum temperatures and soil moisture conditions. All six species exhibited greatest emergence when sown at 0–6-mm depth, with seed size being less important than moisture (except under dry conditions) and proximity to the surface. Species responded differently to the three watering treatments. Eucalyptus melanophloia exhibited greatest emergence in the ‘dry’ watering treatment. The floodplain species, E. camaldulensis, E pilliganesis and E. populnea, had the greatest emergence under flood conditions. Eucalyptus blakelyi and E. melliodora exhibited intermediate emergence in relation to all three soil-moisture regimes. Although the direct seeding of these species in vertosol soils in the region may be successful on occasion, windows of opportunity will be infrequent and the planting of seedling tubestock will be more reliable for revegetation.

Optimising canola establishment and yield in south-eastern Australia with hybrids and large seed

2016 ◽  
Vol 67 (4) ◽  
pp. 409 ◽  
Author(s):  
R. D. Brill ◽  
M. L. Jenkins ◽  
M. J. Gardner ◽  
J. M. Lilley ◽  
B. A. Orchard
Keyword(s):  
Grain Yield ◽  
Seed Size ◽  
Biomass Accumulation ◽  
Simulation Modelling ◽  
Sowing Depth ◽  
Large Seed ◽  
South Wales ◽  
Eastern Australia ◽  
Series Of Experiments ◽  
Seed Characteristics

April sowing of canola is considered optimal for grain yield in many regions of Australia; however, there is often insufficient rainfall in April to sow seed into moisture at the ideal depth of 15–30 mm. We report a series of experiments that investigated the seed characteristics (cultivar type and seed size) that would facilitate successful canola emergence from relatively deep sowing (>30 mm). Ten canola cultivar by sowing depth experiments, each with three hybrid and three open-pollinated cultivars, found hybrid cultivars were able to maintain higher emergence rates and grain yield compared with open-pollinated cultivars from deep sowing. Further investigations in the glasshouse showed that the emergence advantage of the hybrid cultivars was largely due to their inherently large seed size, as increased seed size also improved emergence of open-pollinated canola. Early biomass accumulation also improved with larger seeds. In a field experiment, larger seed size of both hybrid and open-pollinated canola increased early biomass accumulation and final grain yield. Simulation modelling in New South Wales demonstrated the importance of timely sowing of canola, as delayed sowing caused a larger reduction in grain yield than reduced plant population. Although ‘moisture-seeking’ (placing seed into moist soil below a layer of dry soil) reduced the emergence rate of canola, the reduction could be offset by planting large seed (>2 mm diameter). This practice of ‘moisture-seeking’ large-seeded canola should be considered as a strategy to improve the timeliness of establishment and subsequent grain yield of canola when rainfall for crop establishment is marginal yet there is moisture available deeper in the seedbed.

Effects of depth and time of sowing on emergence of Danthonia richardsonii Cashmore and Danthonia linkii Kunth

1993 ◽  
Vol 44 (6) ◽  
pp. 1311 ◽  
Author(s):  
GM Lodge ◽  
AJ Schipp
Keyword(s):  
New South ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Maximum Temperature ◽  
Sowing Time ◽  
Sand Mixture ◽  
South Wales ◽  
Seed Field ◽  
Dry Conditions ◽  
Soil Temperatures

Two experiments examined the effects of sowing time and depth (surface and 10, 25, 50 mm) on emergence of Danthonia richardsonii Cashmore and Danthonia linkii Kunth. Experiment 1 was conducted from January to December 1990 on a loam/sand mixture in boxes. Emergence was highest in both species for seeds sown onto the soil surface in summer and autumn (P < 0.05). Sowing at any depth at any time of the year, or surface sowing in winter and spring, markedly reduced emergence. Experiment 2 was conducted in the field at Tamworth, northern New South Wales from September 1991 to August 1992, on a red brown earth and a black earth. This study confirmed that emergence in both species was highest from surface sown seed. Field emergence was lowest in winter, but in contrast to experiment 1, it was higher in spring, particularly on the black earth. Seedling emergence appeared to be related to mean maximum temperature, decreasing in winter as it declined below 20�C, and increasing in spring when it was greater than 23�C. Differences in seed weight were reflected in emergence of D. richardsonii and D. linkii in experiment 1. Similar emergence was recorded for the loamlsand mixture and sand, indicating that there was little effect of texture. Phalaris aquatica L. cv. Sirosa surface sown in December had lower emergence ( P < 0.05) than both Danthonia spp., but emergence of this larger seeded cultivar was higher at depths of 10 and 25 mm. Laboratory studies to determine reasons for the low emergence of D. richardsonii and D. linkii from depth, indicated that neither had an obligate light requirement for germination. Depth, however, reduced germination (P < 0.05) compared with surface sowing of seed. Seedlings at depth also were observed to have slower rates of shoot and root elongation. In the field, the most successful establishments of D. richardsonii and D. linkii seedlings are likely to occur from surface sowings in April and May. Sowing in spring may also be possible if mean maximum soil temperatures exceed 23�C, and seedlings can establish before the onset of hot, dry conditions in summer.

Effects of soil moisture and temperature on seedling emergence from natural and pre-germinated onion seeds

1986 ◽  
Vol 107 (2) ◽  
pp. 249-256 ◽  
Author(s):  
W. E. Finch-Savage
Keyword(s):  
Soil Moisture ◽  
Water Availability ◽  
Seedling Emergence ◽  
Moisture Stress ◽  
Start Time ◽  
Mean Temperature ◽  
Changing Patterns ◽  
Moisture Conditions ◽  
Germinating Seeds ◽  
Germinated Seeds

SummaryThe emergence of seedlings from natural, germinating and selected uniformlygerminated onion seeds was compared in a range of changing patterns of soil moisture. The timing, spread and amount of seedling emergence from seeds in all three treatments were affected by the timing of water availability in the seed bed and these effects differed between treatments.The rate of seedling emergence in all three treatments under non-limiting soil moisture conditions was correlated with mean temperature, but this relationship was obscured in irrigation treatments where water stress occurred. However, if the seed bed was moist at sowing irrespective of subsequent moisture stress the reciprocals of the time to the start, time to 50% and time to the end of seedling emergence from uniformly germinated seeds were correlated with mean temperature (r > 0·87, D.F. 27).The results show that if the seed bed is irrigated prior to sowing and soil moisture is maintained during the first 3 days following sowing high levels of seedling emergence with both predictable timing and uniformity can be achieved by sowing uniformlygerminated seeds. Seedling emergence from natural and germinating seeds was much less predictable.

scholarly journals The Effect of the Dry Line and Convective Initiation on Drought Evolution over Oklahoma during the 2011 Drought

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Paul X. Flanagan ◽  
Jeffrey B. Basara ◽  
Bradley G. Illston ◽  
Jason A. Otkin
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Warm Season ◽  
Convective Initiation ◽  
Model Simulations ◽  
Variable Surface ◽  
Oklahoma Mesonet ◽  
Dry Conditions ◽  
Moisture Conditions ◽  
The Impact

Observations from the Oklahoma Mesonet and high resolution Weather Research and Forecasting model simulations were used to evaluate the effect that the dry line and large-scale atmospheric patterns had on drought evolution during 2011. Mesonet observations showed that a “dry” and “wet” pattern developed across Oklahoma due to anomalous atmospheric patterns. The location of the dry line varied due to this “dry” and “wet” pattern, with the average dry line location around 1.5° longitude further to the east than climatology. Model simulations were used to further quantify the impact of variable surface conditions on dry line evolution and convective initiation (CI) during April and May 2011. Specifically, soil moisture conditions were altered to depict “wet” and “dry” conditions across the domain by replacing the soil moisture values by each soil category’s porosity or wilting point value. Overall, the strength of the dry line boundary, its position, and subsequent CI were dependent on the modification of soil moisture. The simulations demonstrated that modifying soil moisture impacted the nature of the dry line and showed that soil moisture conditions during the first half of the warm season modified the dry line pattern and influenced the evolution and perpetuation of drought over Oklahoma.

Climatic conditions for seedling recruitment within perennial grass swards in south-eastern Australia

2012 ◽  
Vol 63 (4) ◽  
pp. 389 ◽  
Author(s):  
R. Thapa ◽  
D. R. Kemp ◽  
M. L. Mitchell
Keyword(s):  
Soil Moisture ◽  
New South ◽  
Perennial Grass ◽  
New South Wales ◽  
Climatic Conditions ◽  
South Eastern ◽  
South Wales ◽  
Eastern Australia ◽  
Moisture Conditions ◽  
South Eastern Australia

Recruitment of new perennial grass plants within existing grassland ecosystems is determined by seed availability, suitable microsites, nutrients and climatic conditions, water and temperatures. This paper reports on the development of criteria to predict recruitment events using modelled soil moisture conditions associated with recruitment of species in five field experiments at Orange (Phalaris aquatica), Trunkey Creek (Austrodanthonia spp.), and Wellington (Bothriochloa macra) in central New South Wales, Australia, and the frequency of those conditions during the past 30 years. Recruitment events were recorded when a rainfall event (median 68 mm across the three sites) kept the surface volumetric soil moisture (0–50 mm) above the permanent wilting point for at least 15 continuous days, allowing for, at most, two ‘dry days’ in between. A key finding from our study is that rainfall events creating favourable soil moisture conditions for seedling emergence typically occurred in the second half of February, sometimes extending to early March. Previously it was thought that recruitment would more likely occur through autumn, winter, and spring when rainfall in southern Australia is more reliable. The 30 years’ data (1975–2004) showed that the P. aquatica site had a median of 20 continuous moist days each year in February–March, whereas, there were 16 and 10 days for the Austrodanthonia and B. macra sites, respectively. The probabilities of exceeding seven or 15 continuous days of moist surface soil were 98% and 78% at the P. aquatica site, 91% and 49% at the Austrodanthonia site, and 73% and 30% at the B. macra site, and indicated that some recruitment is possible in most years. These analyses were extended to several sites across New South Wales, Victoria, and Tasmania to estimate the frequency with which recruitment could occur within natural swards. Across these sites, the probabilities of exceeding seven continuous days of soil moisture were >55% and of exceeding 15 continuous days were lower, which showed that suitable climatic conditions exist during late summer–early autumn across south-eastern Australia for a recruitment event to occur. Future research may show that the criteria developed in this paper could have wider regional application.

scholarly journals Hydrometeorological conditions preceding wildfire, and the subsequent burning of a fen watershed in Fort McMurray, Alberta, Canada

2017 ◽  
Author(s):  
Matthew C. Elmes ◽  
Dan K. Thompson ◽  
James H. Sherwood ◽  
Jon S. Price
Keyword(s):  
Soil Moisture ◽  
Management Strategies ◽  
Organic Soil ◽  
Spring Precipitation ◽  
Air Temperatures ◽  
Dry Conditions ◽  
Lowland Forests ◽  
Moisture Conditions ◽  
High Elevations ◽  
Hydrometeorological Conditions

Abstract. The destructive nature of the ~ 590,000 ha Horse River Wildfire in the Western Boreal Plain (WBP), northern Alberta in May of 2016 motivated the investigation of the hydrometeorological conditions that preceded the fire. Historical climate and field hydrometeorological data from a moderate-rich fen watershed were used to identify a) whether the spring 2016 conditions were outside the range of natural variability for WBP climate cycles; b) explain the observed patterns in burn severity across the watershed; and c) identify whether fall and winter moisture signals observed in peatlands and lowland forests in the region are indicative of fire susceptibility. Field hydrometeorological data from the fen watershed confirmed the presence of cumulative moisture deficits prior to the fire. Hydrogeological investigations highlighted the susceptibility of fen and upland areas to water table and soil moisture decline over rain-free periods (including winter), due to the watershed's reliance on supply from localized flow systems originating in topographic highs. Subtle changes in topographic position led to large changes in groundwater connectivity, leading to greater organic soil consumption in wetland margins and at high elevations. The 2016 spring moisture conditions measured prior to the ignition of the fen watershed were not illustrated well by the Drought Code (DC) when standard overwintering procedures were applied. However, close agreement was found when default assumptions were replaced with measured duff soil moisture recharge and incorporated into the overwintering DC procedure. We conclude that accumulated moisture deficits dating back to the summer of 2015 led to the dry conditions that preceded the fire. The infrequent coinciding of several hydrometeorological conditions, including low autumn soil moisture, a modest snowpack, lack of spring precipitation, and high spring air temperatures and winds, ultimately led to the Horse River wildfire spreading widely and causing observed burn patterns. Monitoring soil moisture at different land classes and watersheds would aid management strategies in the production of more accurate overwintered DC calculations, providing fire management agencies early warning signals ahead of severe spring wildfire seasons.

Effect of sowing depth and water potential on seedling emergence of Lupinus species

1996 ◽  
Vol 36 (4) ◽  
pp. 463 ◽  
Author(s):  
CE Wilson ◽  
N Thurling
Keyword(s):  
Water Potential ◽  
Seed Size ◽  
Seedling Emergence ◽  
Percentage Germination ◽  
The West ◽  
Sowing Depth ◽  
Crop Establishment ◽  
Moist Sand ◽  
Different Depths ◽  
Germinated Seeds

Large differences in responses of germination and seedling emergence to water potential and sowing depth were detected among Lupinus species varying substantially in seed size. Seeds of 7 species (L. pilosus, L. atlanticus, L. albus, L. cosentinii, L. luteus, L. angustifolius and L. hispanicus) germinated rapidly in moist sand (-0.05 MPa). Germination of all these species was reduced when seeds were raised in sand in which water potential was increased from -1.0 to -0.5 MPa at 4 days after sowing, and then to -0.2 MPa at 18 days after sowing. Percentage germination after 20 days was much higher in small-seeded species (L. hispanicus, L. angustifolius, L. luteus) than in large-seeded species (L. albus, L. atlarzticus, L. pilosus). Germination responses were related to rate of water uptake by seeds from sand at 0.5 MPa. Seedling emergence of pre-germinated seeds sown at different depths in moist (-0.05 MPa) and dry (-0.3 MPa) sand varied greatly among 6 species. An increase in sowing depth from 4 to 8 cm retarded seedling emergence to a greater extent than a decrease in water in L. piosus, L. luteus, L. cosentinii and L. atlanticus. L. angustifolius seedling emergence was less affected by variation in sowing depth and water potential than other species, although a decrease in water potential had a relatively large effect on seedling emergence from 4 cm. A decrease in water potential also decreased seedling emergence of L. albus more than deeper sowing. Seedling emergence responses of 4 species (L. angustifolius, L. luteus, L. albus, L. atlanticus) were compared in an experiment where dry seeds were sown in dry sand (-0.3 MPa) at different distances above a moist sand (-0.05 MPa) zone in specially constructed trays. Small-seeded species (L. angustifolius and L. luteus) emerged most rapidly from the shallowest sowing (3 cm below the surface, 9 cm above the moist zone), whereas the large-seeded species L. albus and L. atlanticus emerged most rapidly from sowings at intermediate depths (6 and 9 cm). L. albus and L. angustifolius seedlings emerged far more rapidly when sown on the surface of the moist sand (12 cm) than did L. luteus and L. atlanticus, and were far more tolerant of variation in sowing depth. The implications of these findings are discussed with particular reference to improving lupin crop establishment following early dry sowing in the West Australian wheatbelt.

The influence of sowing depth and seed press wheel weighting on seedling emergence of crisp lettuce

1985 ◽  
Vol 104 (3) ◽  
pp. 631-636 ◽  
Author(s):  
D. C. E. Wurr ◽  
Jane R. Fellows
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Seedling Emergence ◽  
Field Capacity ◽  
Considerable Effect ◽  
Wide Spread ◽  
Sowing Depth ◽  
Variable Weight ◽  
Different Depths

SummaryThe effects on emergence and growth of crisp lettuce seedlings as a result of sowing seeds at different depths and pressing them into the furrow bottom with a weighted seed press wheel were examined in three similar experiments in 1982, 1983 and 1984. Sowing depth had a considerable effect on percentage seedling emergence and the spread of emergence times but the pattern of response varied from year to year and appeared to be related to differences in soil moisture content. The most uniform emergence and the highest level of emergence were achieved by sowing shallowly (< 10 mm) with rainfall almost immediately after sowing then keeping the soil moisture content close to field capacity for 2 days. When rainfall or irrigation were delayed, drilling 15–20 mm deep gave more consistent results. Effects on seedling weight and variability of weight were associated with the time and uniformity of seedling emergence. Later emerging seedlings were lighter and a wide spread of emergence times gave seedlings of variable weight. There was virtually no effect on emergence of using additional weights on a seed press wheel.

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