2015 Australian Agronomy Conference
GroundCover™ Issue: 120 | Author: Nicole Baxter
Cropping specialists from around the country gathered in Hobart in September for the 17th Australian Agronomy Conference. Ground Cover’s Nicole Baxter filed the following reports from the conference at which professional agronomists reported on trends, observations, research needs and outcomes
All photos by Nicole Baxter
Peas shine in crop-topping trial
Crop-topping – the in-crop application of herbicides to prevent weed seedset – remains a useful way to manage weeds that have escaped other control measures, New South Wales Department of Primary Industries pulse specialist Dr Eric Armstrong affirmed.
However, Dr Armstrong told agronomists the timing of applying the crop-topping knockdown was critical and should be strategically targeted at or before the milky-dough stage of the weed seed to ensure its sterilisation.
“It is also essential the development of the pulse variety must have reached or passed its physiological maturity to avoid grain damage and associated yield losses,” he said.
“Many current pulse varieties are relatively late-maturing (for example, chickpeas, lupins and Kaspa field peas) and unsuited to crop-topping, but given the diversity of germplasm for development and maturity across pulse species there is scope for selecting early maturing, high-yielding lines suited to the practice.”
In preliminary trials at Wagga Wagga (NSW) in 2014, Dr Armstrong said field peas were the highest yielding, earliest maturing and best adapted pulse for crop-topping.
In particular, the field pea SW Celine was the highest yielding, earliest-maturing and best suited to crop-topping treatment. Its yield and seed size were the least affected by the earliest spray (14 October) and unaffected by the last two sprays (22 and 29 October).
Of the remaining commercial varieties tested, those best suited to crop-topping were PBA Oura and PBA Pearl.
More information:Dr Eric Armstrong,
02 6938 1814,email@example.com
Scope for higher HRZ yields
CSIRO’s Dr Michael Robertson said the results of a consultant survey and comparisons with experimental yields indicate a sizeable production gap between above-average and below-average-yielding growers in the high-rainfall zone.
Dr Robertson led a project in which 15 farm consultants from New South Wales, Victoria, South Australia and Western Australia were interviewed about the perceived constraints to crop production.
In high-rainfall seasons, the results showed there was a yield difference of one to three tonnes per hectare for wheat and 0.5 to 1.5t/ha for canola between above-average and below-average-yielding growers.
The consultants surveyed said poor timeliness of operations was the main reason for the poor yield performance of below-average growers.
Dr Robertson said improved timeliness of sowing, weed and disease control and nitrogen application could reduce the yield gap identified.
“The consultants said growers with above-average yields tend to be more organised and efficient, achieve more effective weed control, are more willing to invest in inputs, and keep or have access to well-maintained machinery for sowing and harvesting,” he said.
In all regions, consultants saw the scope for large gains in yield and productivity by encouraging the growers with below-average yields to adopt the practices and approach of the more successful growers.
Dr Robertson also said consultants thought a lack of up-to-date infrastructure and services in the high-rainfall zone could be constraining the industry’s ability to adopt new technology.
He said the high-rainfall zone was characterised by smaller farms, often with smaller paddocks and undulating terrain. This may be a factor in constraining the adoption of some technologies such as controlled traffic and variable-rate technology that require larger-scale areas to make them profitable.
Dr Michael Robertson,
0417 721 510,
Barley beats wheat when crown rot risk is high
Crown rot is estimated to cost Australian growers $97 million annually. To lower this cost, researchers have evaluated a range of barley and wheat varieties to help growers’ sowing decisions
If forced to plant a cereal crop in a paddock with a high crown rot risk, New South Wales Department of Primary Industries (DPI) researcher Rick Graham told the Australian Agronomy Conference that some barley varieties may yield better than wheat because of higher disease tolerance.
In replicated trials conducted between 2009 and 2014, NSW DPI senior research scientist Dr Steven Simpfendorfer compared the yield performance of the malting barley variety Commander with EGA Gregory wheat in the presence of Fusarium pseudograminearum (Fp), the fungus responsible for crown rot.
In 13 of the 23 comparisons between Commander and EGA Gregory, Commander delivered an average yield benefit of 0.95 tonnes per hectare over EGA Gregory.
According to Mr Graham, barley is generally more tolerant of crown rot than bread wheat as it tends to escape severe evaporative stress during grain filling, which exacerbates disease expression, by maturing earlier.
However, he noted – as the two sowing times at Garah, NSW, in 2013 showed – this escape mechanism depends on sowing time, with all four barley varieties in the trial (including Commander) experiencing a much higher percentage of yield loss from crown rot when sown later (20 to 30 per cent) relative to being sown earlier (6 to 11 per cent).
Although in the trials barley coped better than wheat when both were subjected to the crown rot pathogen, it still needs a planned strategy: “Barley is susceptible to infection by the crown rot fungus and if sown later in its planting window is likely to be filling grain under adverse conditions, which may lead to significant yield loss,” Mr Graham said.
“Despite this, Commander is still likely to be higher yielding than EGA Gregory, which the NSW trial results for Coonamble (2009), Tamworth (2009 and 2014) and Bithramere showed in 2014.”
Mr Graham said research across 11 sites in 2013 and 12 sites in 2014 had highlighted some of the more recently released bread wheat varieties produced higher yields in the presence of crown rot infection than the widely grown but more susceptible variety EGA Gregory.
Replicated trials were also carried out at Tamworth and Garah in 2014 in which a range of barley and wheat varieties were evaluated for their relative yield in the presence of high levels of crown rot.
The Tamworth results showed that Fp infection caused yield losses in the barley varieties ranging from 10 per cent in
La Trobe to 29 per cent in Oxford. In the bread wheat varieties, yield losses ranged from 14 per cent in LongReach Spitfire to 23 per cent in EGA Gregory.
With the exception of Oxford, all barley varieties were higher yielding than EGA Gregory in the presence of high levels of crown rot infection.
“Hindmarsh and La Trobe produced higher yields than the other barley varieties and were 0.71t/ha and 0.72t/ha higher yielding than Commander, respectively,” Mr Graham said.
“All of the newer wheat varieties were higher yielding than EGA Gregory in the presence of high levels of Fp infection, with Suntop (0.73t/ha), Sunguard (0.74t/ha) and LongReach Spitfire (0.85t/ha) providing the highest yield advantages over EGA Gregory.”
Mr Graham said although Garah was a lower yielding site than Tamworth, the trend in varietal yield performance in the presence of crown rot was similar.
At Garah, Fp infection caused yield losses in the barley varieties ranging from 17 per cent in Hindmarsh to up to 31 per cent for Granger. In the bread wheat varieties, yield losses ranged from nil in LongReach Lancer up to 40 per cent in EGA Gregory.
“With the exception of Oxford and Granger, all varieties were higher yielding than EGA GregoryA in the presence of high levels of crown rot infection, with Compass (0.29t/ha), La Trobe (0.38t/ha), Fathom (0.38t/ha) and Hindmarsh (0.54t/ha) all providing significant yield benefits,” Mr Graham said.
“The best barley variety, Hindmarsh, was 0.30t/ha higher yielding than the best wheat variety, LongReach Lancer.”
While growing barley over wheat may potentially maximise profit in the current year, Mr Graham said it would not reduce the crown rot inoculum level because barley is very susceptible to infection.
“Significant yield loss still occurs in the best of the barley and bread wheat varieties,” he said. “Crop and variety choice is therefore not the sole solution to crown rot but just one element of an integrated management strategy to limit losses from this disease.”
02 6763 1176,
For more information see Barley maturity determines crown rot tolerance in this issue's Tactical Cereal Agronomy Ground Cover Supplement.
Study highlights weeds priority
CSIRO’s Dr Rick Llewellyn said Australian grain growers had demonstrated a willingness to invest heavily to avoid large weed seedbanks and consequent yield losses.
He led a team of researchers who conducted a national study of the impact of weeds involving 602 grain growers in 2014 and found 54 per cent had a late-season weed density of less than one per square metre.
Only 11 per cent reported densities of more than 10/m2. This is consistent with previous paddock surveys, which found growers generally only allow low weed densities to survive past mid-season, including populations with high levels of herbicide resistance.
The five most common weeds in crops nationally were annual ryegrass, wild radish, wild oats, brome grass and wild turnip.
Although no-tillage was the most common sowing system, in the southern region 27 per cent of land is cultivated at or before sowing. Weed management was the most important reason for cultivation before sowing. Overall, 71 per cent of growers who sowed after cultivation cited weed management as the main reason for cultivation.
The research found cultivation in fallows for the primary purpose of weed control is more common in northern and central New South Wales and Queensland.
Narrow windrow burning, a practice that can remove about half of the crop residue, is common in Western Australia, but the survey showed its use is increasing rapidly in eastern Australia.
Dr Llewellyn said that the need to manage increasing herbicide resistance means that weed-control practices were having an increasing influence on the cropping system with more growers focusing on weed seed kill and physical methods of control.
GRDC Research Code CSA00043
Dr Rick Llewellyn,
0420 690 861,
More research needed for on-row sowing
CSIRO researcher Dr Margaret Roper said she saw potential for on-row sowing of crops on non-wetting sands, despite the fact that trials had not shown any clear yield benefit.
She said trials in Western Australia had shown on-row sowing, compared with inter-row sowing, increased crop establishment in 2012, but not in 2013.
In both years, conditions later in the growing season were mild enough for crops sown on the old crop row not to show a yield advantage.
“In 2013, crops sown on the old crop row actually yielded less than crops sown in between the old rows, but yields were influenced by a large ryegrass population so the result may not be representative of potential yield,” Dr Roper said.
Nonetheless, she said tests showed soil in the crop rows became less water repellent during the growing season than the soil in the inter-row.
“Where crops are sown on the previous crop row, there is likely to be more organic matter and nutrient accumulation, which could encourage microbial activity, leading to increased degradation of the compounds causing water repellency,” Dr Roper said.
“The soil water content in water-repellent sand was also greater in crop rows than in the inter-row space, and where stubble had been retained.”
Dr Roper said more research was needed to clarify the long-term use of on-row sowing on soil nutrition, organic matter, soil structure and soil-borne diseases on water-repellent soil.
GRDC Research Codes CSP00139, DAW00244
Dr Margaret Roper,
08 9333 668,
Early-sown canola strong in trials
Sowing canola in early April instead of late April appears to be a strategy worth pursuing according to preliminary research.
A study by CSIRO’s Dr John Kirkegaard and the New South Wales Department of Primary Industries’ Rohan Brill showed canola sown from 1 April was able to equal, and in many cases exceed, the yield of canola sown from 25 April.
Dr Kirkegaard presented the results of the research at the 2015 Australian Agronomy Conference.
The research involved a series of replicated ‘canola variety by sowing time’ experiments at Breeza, Trangie, Condobolin, Greenethorpe, Ganmain and Junee, NSW, in 2014.
Commonly grown commercial varieties with a range in phenology were sown at all sites, including hybrids, open-pollinated varieties and herbicide-tolerant varieties.
The sowing dates spanned 1 April to 23 May and usually consisted of four sowing dates about 14 days apart.
All trials were sown into moisture so germination started at sowing rather than on a subsequent rainfall.
At each site, the canola was sown to establish a target population of 45 plants per square metre based on seed size and germination percentage. At some sites a lower plant population (15 plants/m2) was included.
Weeds were managed at each site using recommended herbicides, and crop nutrition was managed using pre-sowing soil tests and top-dressing to guide fertiliser management to avoid nutritional constraints to crop growth.
The researchers found that crop yield at the different sites reflected the amount of water available to crops and the incidenceof frost.
Maximum yield at the sites ranged from 6.0 tonnes per hectare at Greenethorpe (high water availability and no frost) to 1.2t/ha at Condobolin (dry and frosty site).
Dr Kirkegaard said the effect of sowing date and variety was highly significant at most sites.
At Greenethorpe, the earliest sown (1 April) varieties yielded the highest, with yield declining by 50 kilograms/ha every day sowing was delayed.
At other sites, the highest yields were achieved from both early (1 April) and mid-April sowing (10 to 16 April), although the specific variety that achieved that yield varied with site and sowing date.
“For example, at Junee, Ganmain and Condobolin the fastest developing-variety, Hyola® 575CL, suffered a yield penalty when sown on 1 April, but was among the highest yielding in mid-April,” Dr Kirkegaard said.
“In contrast, the varieties Pioneer® 45Y88CL (sown at Junee and Ganmain) and Pioneer® 44Y87CL (sown at Condobolin) had a similar or higher yield when sown in early April compared with mid-April. With the exception of the dry and frosty Condobolin site, overall yields for all varieties declined after mid-April.”
Dr Kirkegaard said the response of specific varieties to early sowing was critical.
He said spring varieties that were relatively slow to develop (for example, Pioneer® 45Y88CL) had their highest (or equal highest) yield from 1 April sowing at all sites, despite the dry spring and harsh late-winter frost at some sites.
However, he noted that varieties that are relatively fast to develop (for example, Hyola® 575CL) should be avoided for early sowing because they flowered early in winter, exposing developing pods to frost, and may also generate insufficient biomass before the reproductive phase to support optimum yields.
“The early sown hybrid varieties used water very efficiently, often exceeding the upper boundaries reported in previous studies,” Dr Kirkegaard said.
“Although the rainfall pattern may have contributed to lower evaporation, other factors contributing to efficient water use were the rapid ground coverage of early sown hybrids, deeper rooting, higher transpiration efficiency and the avoidance of late-season heat and drought.”
He said tactical agronomy packages to manage the risks and costs of early sowing systems (weeds, disease and input costs) were the target of ongoing research.
Dr John Kirkegaard,
0458 354 630,
Nitrogen lift from weed control
Colin McMaster, from the New South Wales Department of Primary Industries, reminded agronomists of the importance of effective summer weed control. He pointed to research in southern and central NSW that demonstrated controlling summer weeds provided 0.56 kilograms per hectare of nitrogen for every extra one millimetre of stored water in the soil profile.
He said the return for controlling summer weeds was between $2.20 and $7.20 for every dollar invested.
“Stored water is valuable because it is stored in the profile (deeper than 30 centimetres) and can become available to crops during the yield-determining stage in the 30 days leading up to anthesis,” Mr McMaster said.
“Summer weed control will also enhance early-sowing opportunities in some seasons, which could increase grain yield by a further 21 to 31 per cent.”
He said summer weeds should be controlled when they are small and actively growing because this lowers the herbicide rate required.
0427 940 847,
Hybrid canola not suited to all areas
CSIRO researcher Dr Heping Zhang said a gross margin analysis of canola varieties had confirmed hybrids were not suited to all areas of Australia.
His study showed hybrids were best suited to environments where rainfall is relatively high (more than 300 millimetres) and the growing season is relatively long.
“In low-rainfall areas with high temperatures during seed fill, hybrids showed little yield advantage over open-pollinated canola varieties,” Dr Zhang said.
“Hybrid Roundup Ready® and triazine-tolerant canola were profitable in medium and high-yielding environments, but they were not profitable in low-yielding environments because the cost associated with seed outweighs the small improvement in yield.”
Dr Heping Zhang,
0477 389 526,
Nutrient management limiting HRZ yields
A study of the factors contributing to ‘under potential’ wheat and canola yields in the high-rainfall areas of southern Australia has identified insufficient applied nutrients as a major cause.
Senior research scientist Brendan Christy, of the Victorian Department of Economic Development, Jobs, Transport and Resources, said many growers in high-rainfall areas were missing out on higher grain yields by being too conservative with inputs.
“The potential yields for wheat in the high-rainfall zone (HRZ) range from 4.5 tonnes per hectare in Western Australia to 11t/ha in south-eastern Australia, and for canola from 3 to 5t/ha depending on location,” he said.
“However, current on-farm yields are often only half to one-third of these values, averaging 2.7t/ha for wheat and 1.4t/ha for canola.”
Mr Christy said field trials by Southern Farming Systems had shown that with adequate inputs wheat crops could exceed 8t/ha. However, interviews with growers and consultants showed they were only targeting about 5t/ha, and applying inputs to reach that target. Aside from low nutrient inputs, other causes of low yields, from the grower survey, included poorly adapted germplasm, periodic waterlogging, soil acidity, disease and inadequate management.
“Our study showed many advisers in the HRZ are relatively new to cropping and have varying levels of knowledge and support in making recommendations,” Mr Christy said.
“Often they do not feel confident to assess crop demands and limitations, predict yield potential or the risks associated with high input systems in a variable climate.”
Mr Christy said recommendations were therefore often conservative, leading to unrealised yield potential, low protein content and lost opportunities.
As a component of the national GRDC-funded project ‘Optimising yield in the high-rainfall zone’, work is underway to address this issue. He said balancing all inputs, including fertility, was essential for optimising yields, increasing profits and improving the efficiency of fertiliser applications.
While nitrogen may be the most common limiting nutrient, Mr Christy said that without balanced nutrition, nitrogen applications may be less efficient and part of this fertiliser investment wasted.
“We are developing a new decision-support tool for the HRZ that draws on a knowledge of known deficiencies, an economic analysis of the optimal level and mix of fertilisers, market and seasonal drivers, and the grower’s individual budget constraints,” Mr Christy said.
He said the tool was being developed and tested with growers and advisers, and a final version would be available by the end of 2017.
0429 334 657,
Wider potential for winter wheat
CSIRO farming systems scientist Dr Lindsay Bell said a modelling study had shown significantly wider potential for dual-purpose winter wheat varieties across all of Australia’s high-rainfall zones.
For most locations, simulated potential wheat yields exceeded six tonnes per hectare, with yield potential highest (8 to 10t/ha average) in Victoria’s south and lowest (5 to 6t/ha average) in Western Australia’s south-west.
“Dual-purpose crops have the capacity to increase overall profitability and productivity by 25 to 75 per cent compared with grain-only crops,” Dr Bell said.
He said the study showed the highest grazing days were achieved from winter wheat varieties sown early (March to mid-April). These could provide 1700 to 3000 dry sheep equivalent (DSE) days per hectare of grazing, which was two to three times higher than from grazing spring varieties (200 to 800 DSE days/ha).
The main obstacle was that locations with Mediterranean climates, such as WA and South Australia, had a lower frequency of early sowing opportunities before mid-April (less than 30 per cent of years).
Dr Bell said that along with sowing early, nitrogen availability needed to be sufficient to maximise the grazing potential of early-sown wheat.
“For example, on average a winter wheat sown in March could produce more than 2000 DSE days/ha when 150 kilograms/ha of nitrogen was available at sowing, while this was reduced to by one-third and one-half when only 100 and 50kg/ha of nitrogen was available at sowing, respectively,” he said.
Dr Lindsay Bell,
0409 881 988,
Variety selection king in irrigated trials
Results of a preliminary study by the New South Wales Department of Primary Industries (DPI) show variety is the key to maximising yields in irrigated wheat.
NSW DPI researcher Tony Napier said the first year of a three-year trial in southern NSW had shown variety had a clear impact on yield.
At Leeton, he said six of the 12 varieties tested in 2014 achieved more than 10 tonnes per hectare, with Suntop and Chara both yielding 10.32t/ha, followed by Kiora, Merinda, Corack and LongReach Lancer.
At Coleambally, Suntop (7.33t/ha) was the highest yielding variety, followed by LongReach Lancer and Chara.
EGA Gregory yielded the lowest at Leeton (8.84t/ha), followed by Mace (9.05t/ha) and LongReach Dart (9.53t/ha). The three lowest yielding varieties at Coleambally were LongReach Dart (5.86t/ha), Bolac (6.60t/ha) and EGA Gregory (6.72t/ha).
At Leeton, Mr Napier said a population of 140 plants per square metre gave a significantly higher yield than a population of 210 plants/m2 when averaged across all other treatments.
However, a variety and plant density interaction was observed. Corack, LongReach Dart and Wallup had a yield advantage at the lower plant population, whereas Chara and Mace performed better at the higher population. There was no effect of plant population on yield at Coleambally.
Mr Napier said the timing of nitrogen application had a significant impact on grain yield and protein.
At Leeton, applying most nitrogen (82 per cent) after the first node growth stage significantly increased grain yield and protein compared with applying most nitrogen (53 per cent) before sowing.
At Coleambally, a separate nitrogen top-dressing strategy was implemented. All treatments had the majority of nitrogen (53 per cent) applied at sowing with changes in top-dressing between the first node and booting growth stages.
The results showed no difference in yield between applying 36 per cent of nitrogen at booting compared to applying 12 per cent of nitrogen at booting.
02 6951 2796,
GRDC Project Code DAV00113, CSP00194, CSA00043, CSP00139, DAW00244, DAN00175, CSP00187, CWF00013, CSP00169, DAV00141, CSP0132, CSP00178
Region National, North, South, West