BACKGROUND
“Life is really simple, but we insist on making it complicated.” Confucius
Farmers have been growing wheat for decades, yet we are constantly changing varieties to avoid the risk of disease and to increase yield. When comparing varieties, it is important to understand which risks are manageable and which are not. For example, in 2010, sowing a variety with some short-term dormancy (e.g. non-sprouting) would have been more advantageous than one resistant to stem rust. The reason is simple: stem rust can be controlled by fungicides; no-one can stop rain falling at harvest time.
The wet summer of 2010-11 increased the likelihood of stem rust significantly affecting susceptible varieties (e.g. Yitpi). Yitpi has been the most commonly grown variety in the Wimmera/Mallee, especially the latter, for more than a decade. If stem rust infection occurred early, controlling the disease could be expensive and time-consuming; not doing so can be even more costly. Most growers opted to sow a proportion of their total wheat area to another variety which had stem rust resistance. There is not one variety without a flaw, which made the decision difficult. If ever there was a year to grow Correll, it was 2011. It is resistant to all three rusts. However, its biggest flaws, revealed to great cost in 2010, were test weight and sprouting, two characteristics that weighed heavily on growers’ minds.
It is important for growers to continue to review their varieties annually, but avoid placing too much emphasis on the previous year. If we can take anything from 2010, it was the value of varieties with a high sprouting tolerance. Though it is true that all varieties eventually sprouted under last year’s conditions, knowing a variety is more likely to tolerate a rainfall during harvest can lessen the pressure.
TAKE HOME MESSAGES
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Magenta (4.2t/ha), IGW3119 (4.0t/ha), Correll (3.9t/ha) and LPG07-1040 (3.8t/ha) topped the yields and were significantly better than Yitpi (3.3t/ha)
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protein levels were between 10.5%-12.2%, achieving APW and H2 grades
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there was no problem with test weight or sprouting in any variety
AIM
To evaluate new and existing wheat varieties to assess their suitability to the southern Mallee/northern Wimmera.
METHOD
Location: Corack
Replicates: 4
Sowing date: 16 May 2011 (harvested 1 December)
Seeding equipment: BCG Gason parallelogram seeder (knife point, press wheels, 30cm spacing)
Target Plant Density: 160 plants/m2
Fertiliser:
16 May – 50kg/ha MAP+Zn (10% N, 21.9% P, 1% ZN)
17 Jun – 90kg/ha SOA (20% N, 24% S)
15 July – 90kg/ha Urea (46% N)
2 Aug – 90kg/ha Urea
Herbicides:
16 May – Roundup PowerMax® (2L/ha) + Sakura (118g/ha)
14 June – Monza® (25g/ha)
22 July – Velocity® (670ml/ha) + MCPA LVE (350ml/ha)
Fungicides:
16 May – Flutriafol® (300ml/ha) on fertiliser
26 August – Prosaro® (300ml/ha) + BS1000 (0.25 v/v)
4 November – Opera® (500ml/ha)
The nineteen varieties sown in this trial were chosen because they are either currently grown or are potentially suitable for the southern Mallee and northern Wimmera. The trial was managed according to best practice with nitrogen (N), herbicides and fungicides applied when required. Table 1 summarises the agronomic and disease ratings for each variety in the trial
The trial was baited for mice after sowing as mouse activity was moderately high.
RESULTS
The trial was exposed to several agronomic challenges such as weeds, pests and diseases. The site was quite badly affected by barley grass and brome grass that, given the dry winter, was relatively difficult to control with pre-emergent and post-emergent herbicides in wheat. Sakura (Group K) and Monza (Group B) were applied to control the grass weeds. Both herbicides are most effective on moist soils. As a result of the insufficient winter rainfall, both grasses were problematic.
Yellow leaf spot was rife early; all varieties were affected to a certain extent. Stem rust was found in susceptible varieties in October following a 17mm rainfall event. Leaf rust and stripe rust were also present in susceptible varieties. Flutriafol on the fertiliser and two in-crop applications (at GS39 and GS80) of fungicide significantly reduced the impact of these diseases.
In terms of phenology, Mace did not appear to be as early as it is classified. Mace is listed as having an early maturity, similar to Axe. Mace in this trial and others flowered at a similar time to Scout and Lincoln, whilst Derrimut was closer to Axe.
The co-efficient of variance (c.v %) is quite high (10.8%) for a variety trial. Such variation is not so surprising, given the establishment issues from mice, moisture and weeds. This has limited our ability to identify with confidence other varieties that may be higher yielding than Yitpi.
Grain yields ranged between 3-4.5t/ha. Magenta, Correll, IGW3119 and LPB07-1040 yielded significantly higher than Yitpi (3.30t/ha) (Table 2). Given that the growing season rainfall at the site was challenging (decile 2 year), the grain yields can be attributed to conserved sub-soil moisture from summer. Figure 1, below, compares the performance of the varieties. Those highlighted in green to the right of the figure indicate that they yielded statistically higher than Yitpi.
In terms of quality, generally the majority of varieties achieved APW, with the exceptions of Yitpi, Gladius and Young all of which achieved H2 quality. Gross income was calculated for each replicate and the mean return found that there was no variety that was statistically more profitable than Yitpi. This is mainly because Yitpi achieved H2 in three out of four replicates, whilst the higher yielding varieties achieved mainly APW. With the price differential between H2 and APW of $30/t, this compensated for Yitpi’s lower yield. Peake and Axe were significantly less profitable than Yitpi.
INTERPRETATION
The results of this trial open up the debate about APW versus Hard varieties. The trial showed that only four varieties (Magenta, Correll, IGW3119 and LPB07-1040) were significantly higher yielding than Yitpi, (despite being the third lowest yielding variety). Yet none of these varieties were statistically more profitable. The gross income was analysed on an individual plot basis. A difference of $91/ha was required to be significantly higher than Yitpi. This is because Yitpi was able to achieve a higher grade (H2) whereas those varieties were mainly APW.
There was no frost damage observed in this trial, despite parts of the Mallee being affected by an event in September. Yield losses of up to 90% occurred in some areas; early varieties performed notably worse. This reinforces the importance of considering the exposure of early and late maturing varieties for the risk of frost and heat stress. It should be noted that when a variety is marketed as a particular maturity (e.g. Early), it is difficult to know exactly what this will mean in terms of when it is actually going to flower, not just ripen. Flowering can vary depending on the time of sowing, nutrition and temperature. If you are sowing a new variety, it would be ideal to compare when that variety flowers in relation to the other varieties grown. This will allow you to know how its maturity fits in your environment.
COMMERCIAL PRACTICE
For the Mallee, there is still not a clear cut replacement for Yitpi. For those who bulked up some Scout last season, it probably has a fit as the wheat-on-wheat variety until we are certain of its returns as the main wheat variety. Wheat grown on wheat stubble is likely to have lower protein; APW varieties could be grown on those paddocks. Other wheat-on-wheat varieties with YLS resistance that could be considered are Magenta (APW) or Mace (AH); the latter is probably going to be better in drier years. Both Mace and Scout will need to be managed for stripe rust, especially Mace. Magenta for the second year in a row topped the yields. It has a potential fit in wheat-on-wheat situations. Wheat grown on canola stubble will be common in 2012. Yitpi and Correll are still acceptable options, but test weight in Correll may be an issue, given the industry standard will rise to 76kg/hc in 2012.
For the Wimmera, Yitpi, Derrimut, Correll, Mitre, Lincoln and Gladius have been the commonly-grown varieties. Scout and Estoc can also be considered as suitable varieties. Mace is probably too early maturing but its yellow leaf spot resistance might be useful if growing wheat on wheat.
Figure 2, has been created to help growers choose a variety for their yield environment. Yitpi, Scout, Axe, Magenta were chosen based on the differences in their performance at given yield potentials. The values have been obtained by averaging the actual yield (expressed as a percentage of site mean yield) of a variety at a particular yield environment. The yield environment in this case is the site mean. For example, if your average wheat yield is 1t/ha, then Scout and Axe should perform well, whilst in higher yielding environments (>3.5t/ha) the Scout and Magenta will perform better than Yitpi and Axe.
Yield, quality, sprouting tolerance and disease resistance should be the key determinants when deciding between varieties. Despite the fact that some varieties require an extra fungicide, the low cost means that they may be more profitable in the end.
Of the new varieties, the most commonly adopted variety in 2011 was Scout. Initial feedback suggested that it yielded similarly to slightly better than Yitpi, but it certainly proved harder to thresh than Yitpi. LPB07-1040 is likely to be superior to Scout in 2013 because it is expected to be classified as Hard and has excellent rust resistance. IGW 3119 yielded well in 2010 and 2011 BCG trials. However, it apparently is difficult to market as it has a tendency to have poor falling numbers, even in the absence of rain during harvest. Emu Rock (bred as IGW 3167) is a potential fit and is likely to be available next year through NuSeed, it will be a Hard variety. Wallup is a new AGT variety which was released late in 2011. It is a Hard variety, with good stem rust and CCN resistance. Unfortunately, it was not included in this trial but is included in the National Variety Trials.
ACKNOWLEDGEMENTS
This project was funded by BCG members through their membership fees.
