As growers have adapted to dryer seasons and later breaks, shorter season wheat varieties have become a common inclusion in Wimmera and Mallee cropping systems. These varieties are better suited to dry sowing, a practice growers have adopted to improve production outcomes and negate the logistic issues associated with late breaks. However, in 2014, an early break in April tempted some growers to sow earlier than usual, and many wondered whether this would be pushing the boundaries of the sowing window. They were right. Much of the region was sown in April last year and crops were subjected to a number of frost events in July and August. Later sown crops, or longer season varieties were less affected by these events.
Since 2010, there has been rapid adoption and turnover of varieties in the search for a Yitpi replacement; fully understanding how best to manage them can be a challenge. Variety comparison research, such as the National Variety Trials (NVTs), can help growers to identify outstanding new varieties. However, it is important to recognise that NVT protocols dictate that early maturing varieties are sown on the same day as longer season varieties. This being the case, the performance of specific varieties is commonly a reflection of the season, rather than how well adapted each variety is to the environment. When NVT varieties are sown late in the sowing window, shorter season varieties have an advantage. While Mace and Corack have been standout varieties in the NVTs in recent years, how well would they perform if sown in April?
In an attempt to answer questions such as this one, and to identify management practices appropriate to each variety, BCG incorporates different sowing times into its comparison trials.
This research is part of GRDC’s stubble initiative, ‘Maintaining profitable farming systems in retained stubble’.
TAKE HOME MESSAGES
- Corack, Cosmick and Correll were solid performers in the Mallee in 2014.
- Mace and Shield were the highest yielding varieties in the Wimmera (Horsham).
- Mace, Scout and Corack topped the variety trial in the West Wimmera (Nhill).
- Corack and Mace have been solid performers for the past three years across the Wimmera and Mallee regions.
AIM
To compare the performance of new and existing wheat varieties in four environments, under different sowing times and varying disease pressures
TRIAL DETAILS
Pests and weeds were controlled to best management practice. In variety only trials (Kooloonong) disease was controlled to best management practice.
Pests and weeds were controlled to best management practice and variety only trials (Nhill), disease was controlled to best management practice
METHOD
Wheat variety trials were established at Kooloonong, Quambatook, Horsham and Nhill. Two sites had additional treatments: Quambatook, disease treatments and Horsham, time of sowing (TOS) as well as disease treatments. Each trial was replicated four times and managed according to best practice. Nitrogen applications were based on crop requirements determined by soil testing and Yield Prophet®. In-season assessments included emergence scores and crop biomass at various growth stages using a hand-held GreenSeeker® crop sensor and a normalised difference vegetative index (NDVI). Grain yield was measured with a plot harvester and grain analysis (protein, moisture, test weight and screenings) was completed on all harvested samples. Statistical analysis was completed using a one-way or two-way ANOVA in Genstat, depending on the trial design.
RESULTS AND INTERPRETATION
With good early rainfall in 2014, prospects for the season looked very positive. Unfortunately, the spring was the second driest on record. There were also several frost events in July and August, (although not measured) resulting in severe stem frost damage to earlier sown crops and particular varieties.
mallee
The Kooloonong trial was sown into a moist seed bed (chickpea stubble) on 25 April with a significant rainfall (15 mm) five days later. Corack, Correll, Cosmick, Kord CL Plus, LRPB Scout, LRPB Trojan, Mace and Yitpi were the highest yielding varieties at this site (Figure 1). The shorter season varieties such as Mace, Emu Rock and Grenade CL Plus, were affected by head and stem frost, a consequence of frost events during July and the temperature falling to minus 2oC on 13 July. The earlier season varieties were at GS33-37, while the later ones were between GS31-32 when the frosts occurred. This may have contributed to the poorer performance of these varieties than in previous seasons.
Low protein was observed in all varieties, indicative of the season and the soil type, and the possibility of insufficient N application. Soil N at the beginning of the season was 54kg N/ha. Test weights and screenings were within specifications for all varieties.
The Quambatook trial was established on field pea stubble and was sown into a moist seed bed (with 13mm of rain at the beginning of May). This trial looked exceptionally promising early in the season. The site received 31mm of rain in September, which enabled it to hang on during the dry spring. Frost damage in Mace was observed (at GS32) during late winter following the frost events in late July, early August (‘Early sowing of wheat’ pp 65). Despite frost damage, a mix of variety maturities topped the yields, including Corack, Cosmick, LRPB Trojan, Mace and Yitpi (Figure 2). Cobra was the lowest yielding, but achieved the highest grain protein (Table 3). It is most likely that this was due to the greater dilution of protein in the higher yielding varieties. Hard wheat (AH) varieties (Mace and Corack) received no advantage over the APW varieties due to quality constraints (low protein).
wimmera
Though the Nhill site was sown later than commercial paddocks in the regions, establishment at the site was very good across all varieties. Corack, Mace, Yitpi, Cosmick, Emu Rock, LRPB Cobra, Shield and LRBP Scout were the top yielding varieties (Figure 3). There was some variation across the site (represented by a high co-efficient of variation, CV%), which limited any differences between the varieties being observed. Grain quality in general was good, with only one variety, Shield, having higher than five per cent screenings. Early maturing varieties were favoured by the drier conditions in spring and the later than optimum sowing. A surprising re sult was that Condo, an early variety, yielded less than other early maturing varieties (early work by AGT has shown its inability to adapt to this region and hence has not been included in NVT’s in the Wimmera).
The Horsham site was sown early for wheat in the region (9 May) and into a moist seed bed after rain. Germination occurred within the following week. Mace and Shield were the highest yielding varieties (Figure 4), closely followed by Cosmick, Corack, Gladius and LRPB Scout. Similarly to Nhill, the Horsham site also had a high CV. Proteins were high for this year (Table 4) which could be attributed to the high starting nitrogen (N) in the paddock (grown on vetch hay stubble). A couple of the varieties had high screenings (small pinched grain), which was attributed to haying off as a result of the season. In a year of limited spring rainfall, early to early-mid varieties yielded best.
(Maturity: E = Early, EM = Early-Mid, M= Mid, ML = Mid-late, L = Late)
time of sowing (tos) – horsham
The greatest difference observed at Horsham between the two times of sowing was in Mace which yielded 0.8t/ha higher at the earlier sowing, (Figure 4). Shield and Corack (both E-M varieties) also yielded better at the earlier time of sowing, with a difference of 0.7t/ha and 0.6t/ha respectively. A two-way interaction was observed between TOS and variety (P=0.001, LSD = 0.3 t/ha, CV 11.7%), highlighting that some varieties are suited to either an earlier or a later sowing. The later sown Mace out-yielded many of the earlier sown varieties, emphasising its suitability to the region with a range of sowing times.
Pushing sowing dates earlier, or, alternatively, late sowing, can cause varieties to perform differently. One management practice to reduce the risk of frost damage is to sow a couple of paddocks with a longer season wheat first, followed by a couple of paddocks with a shorter season wheat, followed by the longer season wheat and so on. This will help to stagger the flowering dates and ensure that not all the wheat flowers in the same week, reducing the risk of widespread frost damage. The maturity of cereal crops is controlled by their response to average daily temperatures (thermal time), but this is moderated by day length (photoperiod) and cold requirement (vernalisation).
At Horsham, sowing early increased yields by 0.4t/ha over the June sowing (Table 4). It was a similar story to that recounted in 2013 at Horsham. An extra 0.4t/ha yield will give an extra $107/ha based on a Wimmera grain price of $268/t (based on AH grade).
wheat disease
Disease pressure was low at the Quambatook site due to a dry spring, but a small yield increase (0.1t/ha) was achieved with multiple fungicide applications (stats P=0.002, LSD 0.06 t/ ha, CV 6.3%). There was no interaction between variety and fungicide application at this site. Subsequently, without a greater yield increase, it would be difficult to justify this commercially. At Horsham disease pressure was also low, resulting in similar findings to those at Quambatook.
previous four years research
NVT results from 11 sites across the Mallee have been averaged and their per cent site mean graphed against each other (Figure 5). Cosmick, Corack, Mace, Shield, Correll and Emu Rock were higher than the trial site mean for the last four years. Cosmick has been represented in NVTs in only the last two years.
Wimmera NVT results have shown similar results to the Mallee trials over the past four years, with the inclusion of Derrimut, another variety which has consistently performed above the site mean (Figure 6).
Varieties of varying maturity groups which are commonly grown were selected to assess their performance over the past four years in different yielding environments (2011 – 2014). In a 1t/ha environment, on average Corack and Mace performed 20 per cent above the site mean. In higher yielding environments they were equal to the site mean (Figure 7), highlighting the fact that Mace and Corack are very adaptable varieties.
However, there are other characteristics which need to be considered when making varietal selections, such as disease resistance and quality specifications. If yield is king, then Corack and Mace are the best varieties to grow. But when quality and associated costs are added to the mix, together with protecting the crop against disease, the issue becomes much more complex.
Conversely in the Wimmera, variety performance over a range of yield potentials is less variable. In these circumstances, growers should put more emphasis on selecting varieties for their whole package and consider other factors such as maturity, disease package and quality in combination with yield.
COMMERCIAL PRACTICE
When choosing a new variety, growers need to look at the complete agronomic package of the variety and the likelihood of it being the best fit for the existing farming system. Growers need to be asking themselves whether adoption of a new variety is really worth considering every year. More often than not the answer will be in the negative.
Key factors to consider are:
- yield
- maturity
- disease resistance
- weed pressure (Clearfield variety)
- quality
The ability to utilise varieties with diverse maturity classifications (Early to Mid to Late) will help growers to spread their risk on-farm. If a portion of the program is sown early, a longer season variety should be considered as well. The different maturity groups will help to stagger the flowering dates to reduce the frost risk to the whole program. In addition to this, the best way for growers to maximise results is by selecting varieties and timing them early in their sowing window.
Growing varieties with a mix of disease resistance capabilities can help reduce risk, as well as reduce the workload of fungicide applications in spring. If a rotation is cereal dominated then perhaps a more resistant variety is more suitable for wheat-on-wheat production. Another aspect to consider is the possibility of the presence of too many Clearfield varieties in the farming rotation, as this generally means another Group B herbicide application.
Choosing a variety for quality versus yield is another decision to weigh up. In some cases in 2014, the advantages of AH varieties were offset by low protein, and profits were no higher than those derived from an APW variety. If AH seems to be unachievable, then yield is king, and perhaps a higher yielding APW variety is the answer.
Which varieties, then, should be grown? Although new varieties have emerged recently, over the last three years Mace and Corack have consistently performed well in the Mallee. Cosmick and LRPB Trojan are also certainly ones to watch in the Mallee and, if looking for a Clearfield variety, Kord CL plus has been a good performer.
In the Wimmera, quite a few varieties have achieved high yields over the last four seasons. In a season with a dry spring, early sown varieties still out yielded those sown later. Mace, LRPB Scout, Shield or Corack are all good performing varieties that are also suited to the Wimmera.
ON-FARM PROFITABILITY
Using the results from BCG trials in 2014, in the Mallee, Mace resulted in an extra 0.1t/ha over Yitpi, or an additional $28/ha (based on Quambatook H1 price of $285/t).
An additional $85/ha was obtained by growing Mace over Derrimut (yielded 2.3t/ha, in the adjacent trial) in the Wimmera in 2014 (based on Murtoa H1 price of $286/t). Mace over LRPB Scout also increased profit by $171/ha in 2014, as a result of the extra 0.6t/ha in yield.
REFERENCES
Victorian Winter Crop Summary 2014 – DEPI
ACKNOWLEDGEMENTS
This research was jointly funded by GRDC through it’s, ‘Advancing Profitable Farming Systems’ project (BWD00024) and Agritech Rural, Horsham.
