By Claire Browne and Jemma Pearl, BCG
Take home messages
- Trojan and Beckom were the highest yielding in the Mallee and Trojan, Cosmick and Scepter
topped the yields in the Wimmera.
- There was a 0.5t/ha advantage in having earlier sowing varieties in the Wimmera (sown on 18 May), over later sowing
- Cosmick, Corack and Mace have performed consistently well over the last six years in NVT, showing their adaptability to these regions regardless of sowing time.
For the past decade, growers have experienced first-hand the advantage of sowing early, which has motivated the question, ‘how early is too early?’.
The ‘just add water’ 2016 season provided an opportunity to assess the performance of wheat varieties in a cold and wet spring, which is in stark contrast to recent seasons where plants suffered from moisture stress.
An increase in area sown to pulses, especially lentils and chickpeas, has resulted in an increased need to manage logistics in a way that ensures crops can be sown within their optimum window. Research suggests higher yields and profit when sown earlier, has resulted in greater competition for the prime sowing positions (25 April – 5 May). This has meant that the position of wheat in the sowing window has changed (Murray 2015).
Vernalisation and photoperiod requirements provide options for both earlier and later sowing
depending on the rotation. There is now a greater abundance of varieties that have different
vernalisation and photoperiod requirements, enabling growers to widen their sowing window
and minimise the risk from frost or heat shock at flowering time.
This article will present the finding of three field trials that compared wheat varieties; one of which compared the performance of varieties when sown at different times.
To compare the performance on new and current wheat cultivars in the Wimmera and Mallee,
managed to maximise yield and to investigate performance at different sowing times.
Table 1. Trial details for Kalkee, Nhill and Warmur.
Replicated trials were established at Kalkee, Nhill and Warmur using a complete randomised
Assessments carried out in-crop included NDVI measurements (measure of canopy greenness) which were conducted at both Nhill (22 June and 31 August) and Kalkee (25 July and 19 October).
Biomass samples were taken from four selected varieties (Corack, Scepter, Trojan and Scout) at flowering (GS65) and at harvest (GS99). Ten stems were also collected at these times for plant partioning, where the stems, leaves and heads were separated and then weighed for each sample (data not complete at time of writing). This was for the purpose of identifying where the varieties put their energy into, ie. stem, leaves etc. and consequently how much stubble is left behind.
The trial at Kalkee had varieties sown at two different times (TOS), giving an opportunity to investigate the effect of sowing time on varieties.
Flowering assessments were conducted at all trial sites.
Results and interpretation
The trial at Warmur was sown into excellent conditions and emerged a few days later. Fungicide sprays kept the trial fairly free from disease infections and a large population of aphids present in the trial were controlled with insecticide. No frost events were recorded at the site.
Flowering dates were recorded on 17 September; Scepter and Cosmick were at GS65 on this day. LRPB Arrow, Kord CL Plus and Mace flowered one week later (23 September). Conditions were conducive to high yields, with the site receiving 120mm during September and cool weather at flowering time.
The two highest yielding varieties in the trial were Trojan and Beckom (Table 2). There was a trend for the early to early-mid varieties to be lower yielding in this trial. Grain protein levels across the trial suggest that further nitrogen was needed. Anecdotally, this was also noticed across growers paddocks in the 2016 season. It is important to note the high yields and soft finish to the season is extremely rare for the Mallee.
Each trial was managed to optimise yields, but nitrogen (N) may have been a limiting factor for many of the varieties in this trial. The site initially had 56kg N/ha, with 64kg N/ha added in two applications during the season, meaning only enough N was supplied for a 3t/ha crop (based on wheats requirement of 40kg N/ha for 1t/ha of grain to be produced).
Mace, in 2016, had a tendency to tiller early and it therefore reached its peak too early and it did not translate into additional yield.
Table 2. Grain yield (t/ha) from Warmur, percentage of site mean and grain quality analysis.
At Nhill, a larger number of varieties were compared, albeit sown 12 days later than the Warmur site. The site received high rainfall for September and October and a frost event occurred mid-October which affected some varieties.
Yitpi was high yielding at 5.4t/ha (Table 3), but not different to DS Pascal, Cutlass, Trojan, Scout and Cosmick (all yielding between 5.3t/ha and 5t/ha). When the frost occurred in mid-October, Yitpi was still at early head emergence and was therefore not affected. Growth stage notes from October also confirm that DS Pascal was not affected by this frost event.
The lowest yielding variety at the Nhill site was Shield. Growth stage data indicated that frost would have hampered Shield’s results and this was confirmed by visual inspection of grain samples. Frost resulted in pinched grain, which did not increase the screenings as the small grain would have been removed with the chaff at harvest. The low test weight (73kg/hL) is also indicative of frost affecting grain yield. In the National variety trials (NVT)’s at Kaniva and Horsham, Shield produced yields of 7.9t/ha and 6.1t/ha respectively.
Table 3. Grain yield (t/ha) from Nhill, percentage of site mean and grain quality analysis.
The Kalkee site received 102mm during the summer fallow period, before the first time of sowing (TOS) on 18 May. Consequently, TOS1 was sown into moisture, emerged five days later and was at the three-leaf stage when TOS2 was sown a month later (20 June). The site received a further 57mm of rain prior to TOS2. The rainfall, together with the relatively warm weather in autumn, was conducive for quick emergence.
The highest yielding early sown varieties were Trojan and Cosmick (Figure 1). Trojan, Scepter and Wallup were the highest yielding varieties sown later (TOS2). On average the top five yielding varieties gained an additional 0.5t/ha when sown earlier (Table 4). Grain protein per cent was higher in TOS2, (which can be attributed to a yield dilution effect) however, proteins were generally quite low across the site. All varieties except Wallup and DBA Aurora, yielded higher in TOS1.
Figure 1. Wheat time of sowing comparison of yield (t/ha) at Kalkee.
Table 4. Grain yield (t/ha) from Kalkee for TOS1 and TOS2 and grain quality analysis.
Previous research has shown, earlier sowing dates consistently achieved greater yields than sowing later (Murray, 2015). Even in a favorable spring we observed differences between varieties when sown early and later. In the case of Trojan, yield was 0.6t/ha higher from sowing early (Table 4). This is due to the early sowing allowing more biomass to be produced, translating to grain. As wheat will not tiller like barley, sowing into warm moist conditions (eg. early May) means crop growth will potentially lead to greater tiller production.
NVT LONG-TERM DATA
As per the BCG TOS results in 2016, NVT data over the long-term has also demonstrated that sowing earlier has a positive effect on grain yield (Figure 2).
NVT yield data is expressed as a percentage of the varieties actual yield over the varieties long-term yield (2011-2016). Data above the dotted line indicates a yield result above the long-term average for the variety. Figure 2 clearly shows that varieties sown early have consistently performed better in the Mallee NVT.
Figure 2. Per cent of long-term yield at different sowing times, 2011-2016 Mallee NVT data.
According to the long-term NVT data Cosmick, Corack, Shield, Emu Rock and Mace, which represent a mixture of maturity groups, have performed above the site mean consistently for the last six years (Figure 3).
Variety yield results in 2016 show that seasonal differences are a significant driver of yield that can not necessarily be managed by growers. Therefore, when considering varieties, assessing long-term results can provide growers with confidence on how a variety has performed over a number of years.
Figure 3. Average Mallee NVT and BCG wheat yield as a per cent (%) of site mean from 2011-2016 for 11 varieties at Balranald, Berriwillock, Birchip, Chinkapook, Hopetoun, Jil Jil, Kooloonong, Manangatang, Merrinee, Murrayville, Pinnarroo, Pira, Quambatook, Ultima, Walpeup, Warmur, Watchupga East and Woomelang. Note: Cosmick has only been in the NVT since 2013.
Yitpi and Phantom were the only varieties in the Wimmera to yield higher in 2016 compared to the long-term average (Figure 4).
Corack and Mace yielded considerably lower than the long-term average, mirroring results in the Mallee and suggesting they are more suited to a lower GSR season and/or a tighter finish.
Figure 4. Average Wimmera NVT and BCG wheat yield as a per cent (%) of site mean from 2011-2016 for 11 varieties at Brim, Corack, Horsham, Kalkee, Kaniva, Minyip, Nhill and Yanac.
Wheat variety data from 2016 can provide information about which varieties are able to capitalise on spring rainfall. When coupled with data from the more recent dry seasons, growers can get an understanding of which varieties suit their environment over a longer time frame. It is important not to fall into the trap of ‘chasing rainbows’ by continually changing varieties. Make sure you have ticked all the other agronomic boxes first (such as the right nutrition, sowing time, establishment, weed, pest and disease control) and when considering a new variety, ensure that you understand its adaptability across multiple seasons and regions.
With an increase in pulse production, particularly in the Mallee, compromises have to be made to ensure that sowing time is optimal to maximise whole farm profitability. For many this has meant a shift in the sowing time for wheat, not only for logistical purposes, but in order to make the greatest return from pulses possible. With the wide range of wheat varieties and maturities available, growers can extend the sowing window, without placing significant pressure on the system.
The 2016 season was certainly a forgiving year that allowed later sown paddocks to perform almost as well, or even equally well, as their earlier sown counterparts. This result is contrary to the past 10 seasons where early sowing has consistently produced a significant yield benefit between TOS.
Trojan is one variety that has consistently suffered a yield penalty when sown later while Corack, on the other hand, can withstand later sowing without losing yield.
The yet to be released winter wheat RAC2341 also looks promising. It can be sown earlier and potentially a longer season option in the future. DS Darwin, a newly released line, has the ability to adapt its maturities to the season, particularly in regards to head emergence.
Cosmick has consistently performed well over the previous three seasons, and in this trial, it produced good yields at both sowing times. There is now sufficient evidence to justify selecting Cosmick over other varieties in both the Wimmera and the Mallee.
Trojan and Corack have also been good performers, but being APW varieties, they are less attractive than Cosmick. Trojan is favoured more towards the earlier sowing opportunity or favourable seasons, while Corack has performed well across a range of sowing times and seasons.
Using these varieties as part of the sowing plan will enable other crop types, such as lentils and chickpeas, to be sown at their optimal timing, usually the first week of May. This would have a positive effect on the whole farm profitability.
The catch-cry ‘yield is king’ continues to reign supreme as wheat variety selection decisions are made. Undoubtedly, yield remains a main driver of profitability, however, as farms get bigger, selecting varieties that perform well over a wider sowing window is becoming increasingly important. It is impossible to physically sow every crop on the ideal day, so including wheat varieties in the rotation that can be sown earlier or later can be advantageous, particularly as more pulses are being sown earlier.
In this trial, Corack’s yields were not influenced by sowing time, while Derrimut performed better when sown earlier, demonstrating a good fit for two varieties in a program seeking to widen the sowing window. This follows the same trend as shown in previous BCG research (Murray 2015).
Corack, when sown later, achieved an average gross income of $1112/ha (6.6t/ha). The average income from Derrimut when sown early was $1139/ha (6.8t/ha), which was similar to that of the later sown Corack (this would be different in a season where higher proteins were achieved).
Including these wheat varieties into the cropping rotation would provide growers with an opportunity to extend the sowing window.
Hochman Z, Gobbett D, Holzworth D, McClelland T, van Rees H, Marinoni O, Navarro Garcia J, Horan H (2012) Quantifying yield gaps in rainfed cropping systems: A case study of wheat in Australia. Field Crops Research, 136, 85-96.
This trial was funded by the GRDC as part of the ‘Maintaining profitable farming systems in retained stubble’ project (BWD00024) and BCG members through their membership.
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