- Correctly matching wheat variety to optimal sowing date helps growers minimize the risk of yield loss through frost at flowering and heat stress at grain fill.
- Variety response to sowing time data can be used to match variety and sowing date.
- Trials have highlighted the variability of variety responses to sowing dates.
- Growers are encouraged to retain a number of varieties with a range of maturities as part of a risk management strategy.
Matching wheat variety response to sowing time can be an effective risk management strategy for northern growers looking to minimise yield losses from frost at flowering and heat stress at grain fill.
NSW Department of Primary Industries (DPI) research agronomist Rick Graham said variety response to sowing time data could be used to better match variety to sowing date and maximise crop yield potential and profitability.
Addressing advisors and growers at the recent Grains Research and Development Corporation (GRDC) Grain Research Updates at Coonabarabran and Goondiwindi, Mr Graham and co-presenters research agronomist Dr Peter Martin and NSW DPI Manager Northern Cropping Systems, Dr Guy McMullen, reported that trial results had demonstrated the importance of targeting varieties to their appropriate sowing window, taking into account potential yield penalties of early sowing or delayed sowing past the optimum window.
They observed that genotype yield response curves could also help quantify varietal response to sowing date and assist growers in varietal selection.
“Given the variability of the seasonal break and hence the sowing window in any given season, growers should be encouraged to retain a number of varieties with a range of maturities (yield response curves), to ensure that yield potential is maximised and risk is minimised,” Mr Graham said.
“Importantly, when considering variety selection, growers and advisors need to consider a wide range of information including long term National Variety Trial (NVT) analysis results, market demand and disease ratings.”
The combination of variety and sowing date determines the probable timing of environmental stresses such as frost and heat at key developmental stages of the crop, including anthesis (flowering period) and during the critical post-flowering grain fill period.
Put simply, wheat needs to flower when the probability of frost at flowering and heat stress during grain filling are as low as possible.
Varieties with large differences in maturity have been released by breeding programs. This maturity difference allows the late maturing varieties to be sown when the break is early and the earlier maturing varieties to be sown when there is a late break.
However the relative maturity of a variety does not remain consistent across different sowing times and locations.
Maturity of wheat varieties is controlled by vernalisation (Vrn) and photoperiod (Ppd) genes and Australian varieties are classified according to the presence of some of these genes.
Variety response to changes in sowing time has been estimated using data from both sowing time and NVT and this data is utilised in resources such as the NSW DPI & GRDC publication, Winter Crop Variety Sowing Guide 2015, to help growers select the most appropriate variety for their expected production conditions.
Mr Graham said the optimum flowering window was considered an agronomic compromise between avoiding excessive yield loss due to frost and ensuring that flowering occurs early enough to allow a long grain fill period before heat and moisture stress reduce yield.
“Early maturing varieties sown before their recommended sowing window predisposes them to increased risk of frost as well as quickening crop development,” he said.
“On the other hand, earlier than recommended sowing of mid to late maturing varieties, can increase total plant biomass pre-anthesis, potentially reducing the amount of plant available water for grain fill.”
Over the years, a number of variety response to sowing time trials have been conducted as part of the GRDC-funded Variety Specific Agronomy Packages (VSAP) project.
This has helped to determine how new varieties compare in maturity and yield with existing varieties across the sowing window at a regional level, and given growers a tool to better match variety with sowing time.
During the GRDC Update presentation, Mr Graham used three case studies from VSAP sowing date experiments on the Western Plains, Liverpool Plains and the North West Slopes and Plains to demonstrate the variability of variety responses to sowing dates.
The trials assessed the yield and gross return implications of planting six varieties – EGA Eaglehawk, EGA Gregory, Lancer, Spitfire, Dart and Suntop - across a selection of planting dates at Trangie, Narrabri and Tamworth.
In each case, the trials highlighted the value of adopting varieties according to their appropriate sowing windows.
While some varieties yielded well across a range of sowing dates, in most cases the yield advantage of planting outside the optimum window was small but the potential yield penalty was significant.
“Over time, these trials provide greater confidence in varietal performance estimates and flowering behaviour,” Mr Graham said.
“Recent results suggest for example, that Lancer can vary in maturity relative to EGA Gregory (either earlier or later), depending on sowing time and prevailing seasonal conditions. Suntop has also been observed to vary in relative maturity with changes in location and sowing time.
“Variety selection for a given sow time opportunity and the potential implications of those decisions in terms of risk management are critical issues for northern growers given that the autumn break and subsequent sowing window in NSW can occur anywhere between March and June.
“There are also wheat varieties with a wide range of maturities available to growers in NSW and QLD, which coupled with no till farming systems, has increased the length of sowing date opportunities.
“Knowing what varieties are available to suit individual planting opportunities is critical if growers are to maximise their crop’s production and profitability potential.”
Details on the trial results can be found in the 2015 GRDC Update papers section of the GRDC website or in the NSW DPI publication Northern Grains Region Trial Results Books.
Caption: NSW Department of Primary Industries (DPI) research agronomist Rick Graham sowing trials at Condobolin.
Bernadette York, media officer NSW DPI
0427 773 785
Sarah Jeffrey, Senior Consultant, Cox Inall Communications
08 9864 2034, 0427 189 827
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