Matthew Gardner¹, Rohan Brill² and Guy McMullen¹

¹NSW DPI Tamworth; ² NSW DPI Coonamble

Background

Broadly, this paper will report on a range of agronomy trials conducted throughout the region from 2008 to 2012. Primarily trials are associated with the Variety Specific Agronomy Packages (VSAP) project that aims to close the yield gap between seasonal potential and achieved yields through optimising the agronomy of key wheat, barley and canola varieties. This paper is divided into four sections:

1. Plant Growth Regulators (PGRs) and lodging management

2. Delayed harvest

3. Nitrogen management in barley

4. Wheat Nitrogen Use Efficiency (NUE)

5. Time of Sowing and New Varieties

1. Plant growth regulators and lodging management

Plant growth regulators (PGRs) have been used routinely in high input, high yielding cereal systems in Europe and NZ for some time to shorten straw height and reduce the incidence of lodging. Lodging results in significant losses in crop production due to reduced movement of water, nutrients and translocation of plant stored carbohydrates through the stem into the head. Lodging also reduces grain quality, increases harvest losses and the actual cost of the harvesting process. Although Gibberellin inhibitors and Ethylene producers are the two main PGR groups, the research presented here only investigated Gibberellin inhibitor products. These products act by blocking gibberellin biosynthesis to reduce internode length in stems thereby decreasing plant height. There are a number of phases in this pathway and different PGRs act at different points. For example chlormequat (Cycocel) acts early in the pathway while more recently developed products such as trinexapac-ethyl (Moddus) act on later stages.

PGRs have also been reported to have a yield enhancement effect by improving the proportion of crop dry matter that is partitioned into grain yield. This effect has been related to a reduction in the plant resources required for stem elongation with these resources then available for grain-fill. Some PGRs have also been associated with increased root growth resulting in improved water extraction from soil. Yield responses to PGRs can be highly variable with responses ranging from -40% to +20% depending on product choice, application time, crop or variety and growing season conditions.

What did we do?

In the 2011 and 2012 seasons a series of trials were conducted to investigate the capacity of PGRs to reduce lodging in Commander (high yielding with poor straw strength) barley. In both seasons Commander and Oxford (high yielding with good straw strength) were grown at a target plant population of 120 plants/m²  with four treatments of: nil PGR, Cycocel® (0.2 L/ha), Moddus® (1.0 L/ha) and a combination of Cycocel (0.2 L/ha) + Moddus (1.0 L/ha). PGRs were applied in each season during stem elongation (GS31) at a 100 L/ha water rate. In 2011, sites were established at Tamworth and Spring Ridge, while in 2012 sites were at Moree and Breeza. Please note that at the time of writing, Moddus is not commercially available and is not currently registered in Australia for these use patterns.

What did we find?

Although in 2011 the Tamworth site had lower lodging compared to Spring Ridge the trends were similar (Table 1). The lodging severity for Commander was approximately 3 times what was observed for Oxford, again highlighting the importance of variety selection in lodging management (Table 1). The combination of Cycocel + Moddus was the most effective PGR treatment at reducing the severity of lodging compared to the control treatment (Nil PGR) (Table 1).  

Table 1: Lodging scores (Scale 0-9, where 0 is standing and 9 is flat on the ground) at harvest for the Spring Ridge and Tamworth sites in 2011.

The ability of PGRs to reduce the severity of lodging appears related to their capacity to restrict plant height (Figure 1a). At Spring Ridge (2011) and Moree (2012) the Cycocel +  Moddus treatment was the most effective at reducing plant height  (Figure 1a and 2a). As a single product, Moddus restricted plant height to a greater extent than Cycocel® at both sites (Figure 1a and 2a). There was a large difference between the extent of height reduction measured at the two sites with the maximum height reduction being 7 cm at Spring Ridge in 2011 compared to 34 cm at Moree in 2012. At the Spring Ridge site the treatments containing Moddus had no impact on yield compared to the nil treatment, whereas, the Cycocel treatment significantly increased the yield of Commander by 8 % compared to the nil treatment (Figure 1b). The large reduction in plant height at Moree for the Moddus and Cycocel + Moddus treatments resulted in a significant reduction in yield of 8 and 13 %, respectively (Figure 2b).

Figure 1: The effect of three PGR treatments on a) plant height and grain yield b) of Commander compared to a nil PGR control at Spring Ridge in 2011.

Figure 2: The effect of three PGR treatments on a) plant height and grain yield b) of Commander and Oxford compared to a nil PGR control at Moree in 2012.

In 2008 a trial conducted at the Tamworth Agricultural Institute found a significant yield increase with early applications (GS25) of a PGR combination of Moddus and Cycocel in the absence of lodging. These increases occurred in both durum (EGA Bellaroi) and wheat (EGA Gregory) while no effect was found in Gairdner or Fleet barley. The later application timing resulted in no significant differences compared to the control.

Figure 3: Effect of Moddus and Cycocel timing and rate (mL product/ha) on grain yield of durum (EGA Bellaroi) and wheat (EGA Gregory) at TAI in 2008. (* indicates significantly different from 0 Control)

PGR conclusions

In all trials PGR treatments were shown to reduce lodging to some degree, which was most likely a function of the reduced plant height obtained from PGR applications. Reductions in plant height associated with PGR application were generally moderate (3 to 15 cm) with the exception of the Moree site in 2012 where height reductions up to 35 cm were recorded. Yield responses to PGR application ranged from -13% to +16% in the barley and wheat trials across seasons. The grain yield and plant height results highlight the variability in responses to PGR application, which makes it difficult to accurately predict economic benefit of using PGRs within a cropping system. Of the PGR treatments the combined Cycocel + Moddus treatment resulted in the most consistent reduction in plant height, which is likely due to the two products blocking Giberellin production at different parts of the synthesis pathway. Further research is needed to understand the influence that PGRs are having on crop structure, tiller formation, root growth and soil water extraction in winter cereal crops in the northern grains region.

2. Delayed harvest

The 2010 and 2011 seasons experienced above average rainfall during grain-fill and into harvest in many regions of central and northern NSW. Wet weather can cause significant delays in harvest, either from paddocks being too wet for machinery traffic and/or high grain moisture. In addition to rainfall, the temperature often falls during a wet harvest, which increases the danger of pre-harvest sprouting. Pre-harvest sprouting is a serious problem in cereals resulting in downgrading of grain and heavy financial penalties to the grower. Varieties with dormant genotypes can be used to reduce downgrading caused by rain and, in combination with improved harvesting practices, the risk of weather damage from rain delayed harvest can be minimised. In barley it must be noted that dormancy which persists beyond harvest is highly undesirable because it prevents malting of newly received barley. In current Australian barley varieties, levels of dormancy are very low, and generally are only expressed when cool, wet weather conditions occur.

What did we do?

A trial was conducted in 2011 to investigate the impact of delaying harvest due to wet weather conditions on barley grain yield and quality and whether there was any difference between 12 varieties. This experiment was repeated in 2012 but expanded to include 16 wheat and 15 barley varieties in separate trials.

Each trial had four harvest dates with the 1^st aimed at removing grain before any weather damage had occurred, whereas harvest dates beyond this point were timed to occur after rainfall events. Harvest dates and the rainfall between harvests are outlined in Table 2. Grain quality parameters were determined on a sub-sample from each plot. Unfortunately, grain quality data was not available for 2012 trial at the time of writing this paper.

What did we find?

Table 2: Harvest dates and the quantity of rainfall between each harvest date for the 2011 and 2012 harvest date trials.

The yield penalty associated with delaying harvest from date 1 (11 Nov) to date 4 (7 Dec) varied significantly between barley varieties in 2011. Fitzroy and Buloke incurred the greatest yield penalty (2.2 and 2.1 t/ha, respectively) of the 12 varieties, whereas, Roe, Vlamingh and Grout (0.5, 0.7 and 0.7 t/ha, respectively) had the smallest losses (Figure 4). Commander, Gairdner, Hindmarsh  and Shepherd all had similar yield losses (average 1.2 t/ha) from delaying harvest at Tamworth by 26 days, during which 215 mm of rainfall occurred.

Figure 4: Yield loss between harvest date 1 and harvest date 4 for 12 barley varieties at Tamworth in 2011.

Delaying harvest had a significant effect on all grain quality attributes (Table 3). Protein increased by up to 0.8% between either harvests 1 or 2 and harvests 3 and 4. The 1000 grain weight was similar for harvests 1 and 2, which were significantly higher (2.1 g) then both harvests 3 and 4. Retention significantly increased from harvests 1 and 2 to harvest 3 with a further significant increase associated with delaying to harvest 4. Screenings were negligible across the 4 harvest times but did significantly decline across the later harvest times. Test weight significantly declined by 3.1 kg/hL between harvest 1 and 2 before declining a further 2.7 kg/hL for harvests 3 and 4, which were similar.

Table 3: The effect of harvest time on grain quality traits, protein,1000 grain weight, retention, screenings and test weight averaged across 12 barley varieties at Tamworth in 2011.

**Any values designated with different letters within a column are significantly different (P<0.05).

On average, yield loss between harvest date 1 and harvest date 4 was 0.9 and 0.6 t/ha for the barley and wheat trials in 2012, respectively. Similar to what was observed in 2011 in barley there was a significant difference in yield loss with delayed harvest between varieties for both wheat and barley. Fathom, Oxford and Bass  were least affect by delaying harvest while Navigator  appeared to be the most affected. LongReach Crusader and EGA Gregory had greater yield losses with delayed harvest than all other varieties except for the experimental line LPB07-0548. Once grain quality data is available it will assist in further explaining differences between varieties. 

Figure 5: Yield loss between harvest date 1 and harvest date 4 in 15 barley varieties (a) and 16 wheat (b) in 2012.

Delayed harvest conclusions

The 2010 – 11 seasons represented wet harvests that resulted in significant downgrades in grain quality and price received for grain at the silo. These trials have given an indication of what the penalties are for weather delayed harvest in barley and wheat and the differences that exist between varieties. In reality growers have little choice in the matter and would harvest if conditions, paddock or grain, would permit. However, if weather is imminent, this information may allow growers to prioritise the harvest of paddocks containing varieties which have the greatest risk of negative impacts (yield and quality). Equally, this information may be useful for growers to consider at the start of the season when selecting varieties for sowing to spread their risk against unfavourable weather conditions during harvest.

3. Nitrogen management in barley

The ability to achieve malt, when a suitable variety has been selected, can result in significant financial advantages in some seasons when producing barley. To meet malt specifications growers should target protein levels of 10.5 – 12% to achieve maximum yield and still meet receival standards. As the rate of N supply is increased, yield will generally increase to a maximum level, whereas protein may continue to increase with further N application. Drier or wetter than expected seasonal conditions can significantly change yield potential mid-season, which consequently changes N requirements to meet target protein contents. Therefore, the flexibility of delaying N application to in-crop timings can be a risk management strategy for growers to adapt to changing seasonal conditions. When considering in-crop N applications it is critical to know what soil N levels are available at the start of the season. Many paddocks may have high starting soil N levels well in excess of what is required to achieve realistic target yields and maintaining grain protein levels suitable for the production of malting barley.

What did we do?

In 2011 there were three N sites, located near Walgett, Bithramere and Moree in the northern grains region of New South Wales. Commander, Bass , Navigator  and Gairdner barley, were grown at a plant population of 100 plants/m² at all three trials sites in 2011. In each trial 4 rates of N were applied at sowing including 0, 40, 80 and 120 kg N/ha as granular urea (46 % N). Two additional N treatments were implemented, 80 kg N/ha applied at growth stage 31 (GS31 - stem elongation) and a split application treatment where 40 kg N/ha was applied at sowing with a further 40 kg N/ha applied at GS31. The in-crop application of N was applied as 50% diluted liquid UAN, applied through streamer bars at 100 L/ha water rate.  

What did we find?

For the purposes of this paper only the Bithramere and Moree sites are presented. At both sites Commander had the highest yield on average compared to the other varieties. Bass  and Navigator  had similar yield to Gairdner in these trials.  There was a significant N response at both sites, although much stronger at the Moree site. The split N application gave similar yields as the 80 kg N/ha up front treatment at both sites and for the respective varieties except with Commander at Bithramere where the split N treatment provided an 8% yield benefit (Figure 6). Delaying N until stem elongation resulted in a significant decrease in yield for Gairdner, Commander and Bass  at Moree, whereas, at Bithramere there was no significant difference between the delayed N treatment and the 80 kg N/ha upfront. The protein responses were relatively linear at both sites but there were significant differences between treatments. Commander had the lowest protein content of all varieties, virtually across all N rates (Figure 6c and 6d). Gairdner has been found in previous studies to achieve approximately 1-1.5% higher protein than Commander with the same N input, which was again the case at Moree and Bithramere in 2011. Bass  on average had the highest protein across the two sites and was approximately 0.4% higher than Gairdner. Delaying or split applications of N at Moree significantly reduced grain protein compared to the upfront application of 80 kg N/ha.     

Figure 6: The yield and protein responses of Commander, Bass , Navigator  and Gairdner barley to six N treatments at Bithramere (a, c) and Moree (b, d) in 2011.

Barley N management conclusions

There has been a trend for new barley varieties to achieve lower proteins; however, both Navigator  and Bass  appear to be more protein responsive to N applications compared to Commander. The low protein of Commander has generally been an advantage to meet malt specifications, however, over the past couple of seasons extremely low proteins have been achieved throughout the region (<9%) suggesting that yield may have been sacrificed at this level. The higher protein achievement of Bass  and Navigator  indicates that growers may need to be careful growing these varieties on paddocks with high levels of residual N as it may jeopardise achieving malt specifications. Further analysis of grain quality will determine whether Bass  or Navigator  produce high screenings and low test weights under high N situations similar to Gairdner.

4. Wheat nitrogen use efficiency

Efficient use of N is crucial to economic wheat production, with the risk and reward trade off with applied N being more marginal for western regions. Excessive application of N may increase the susceptibility of the crop to disease and increase water use early in the growing season whereas insufficient application may limit grain yield, grain protein and subsequent profitability. Within a given season in a cereal crop, fertiliser rate and timing are the major tactical tools used in N management. Applications of N at sowing or up to the start of stem elongation drive greater crop biomass and grain yield response in comparison to late applications (around flowering i.e. GS61) which have little influence on grain yield but can drive a significant protein response.

Grain protein levels have continued to gain attention moving into 2013 with the 2012 season making what could be considered to be the third low protein season in a row for much of the northern grains region. Receivals in some areas throughout the region have been dominated (60% in some areas) by low protein wheat (<10.5%) in 2012. Reasons that explain this low protein achievement are discussed elsewhere in the proceedings. It is generally considered that there are only minor differences among commercial varieties in regard to grain protein accumulation. The results from the 2011 VSAP trials indicated that most varieties conform to the yield protein trend where with increasing yield there is a decline in grain protein levels. One variety that appears to be significantly different to this trend is LongReach Spitfire  which appears to achieve a higher protein level for a given yield compared with other varieties. Despite results from trials in 2011 there is still a common misconception that EGA Gregory has lower grain protein accumulation relative to other varieties.

What did we do?

Six nitrogen use efficiency (NUE) trials were conducted in 2012 at Trangie, Coonamble, Wellington, Wongarbon, Moree and Spring Ridge. These trials consisted of a number of varieties with 4 (EGA Gregory, Suntop, LongReach Spitfire  and Livingston) being consistent  across all sites. In four of the six sites there were 4 upfront N rates (0-160 kg N/ha) and two split application treatments with half applied at planting and the other half applied at either stem elongation or anthesis. The other two trials evaluated only upfront N treatments.

What did we find?

Averaged across all nitrogen rates, EGA Gregory and Suntop were the highest yielding varieties and LongReach Spitfire  had the highest grain protein concentration (Table 4). The higher grain protein concentration evident in LongReach Spitfire  is partly due to the negative correlation between grain yield and grain protein concentration; however where LongReach Spitfire  had similar yield levels as EGA Gregory (Coonamble and Moree) it also had an increase in grain protein of at least 1 % over EGA Gregory. Suntop performed relatively well for grain yield, but did not display a grain protein advantage over EGA Gregory. The protein advantage of LongReach Spitfire  on average was 1% greater than the other varieties in the trials, which is consistent with previous findings from the VSAP project and NVT data. 

Table 4: Grain yield (t/ha) and grain protein concentration (%) of four wheat varieties averaged across varying nitrogen rates in six VSAP nitrogen trials in 2012

The N removal on a varietal basis for the Moree and Spring Ridge sites are presented in Figure 7a. LongReach Spitfire  had a 2% protein advantage over EGA Gregory at the Spring Ridge site, which enabled it to remove significantly more N compared to all other varieties with the exception of Suntop. EGA Gregory had similar N removal to all other varieties. At the Moree trial site there was no significant difference in N removal between LongReach Spitfire , EGA Gregory, Suntop or Livingston. However, LongReach Spitfire  had significantly higher N removal than Sunvale and Caparoi, both of which had reduced yields at high N rates at Moree. Figure 7b highlights that LongReach Spitfire  is an outlier when considering the relationship between grain yield and protein. EGA Gregory is not a poor grain protein accumulator compared to other varieties, its protein levels are simply a dilution associated with increased yield. LongReach Spitfire  is the exception in that it appears to have improved grain protein accumulation which is less sensitive to dilution with increasing yield which warrants further investigation.

Figure 7: a) Grain N removal of six wheat varieties at Moree and Spring Ridge when averaged across six N treatments, and; b) the linear relationship between grain yield and grain protein at Spring Ridge for six wheat varieties in 2012.

The split applications of N where the second N application occurred at stem elongation achieved similar yields compared to the same total rate of N applied at sowing.  The only exception was at Spring Ridge, where splitting the 80 kg/ha N rate into 40 kg/ha at sowing followed by 40 kg/ha at stem elongation resulted in higher yield for EGA Gregory and Suntop compared to where 80 kg/ha of N was all applied at sowing. At the Moree and Spring Ridge sites applying 40 kg N/ha at sowing and a further 40 kg N/ha at anthesis did not increase grain protein compared to all N at sowing or the earlier split application timing treatment. The lack of protein response to an anthesis application of N is most likely due to the lack of rainfall after that application to facilitate root uptake.

Wheat NUE conclusions

EGA Gregory and Suntop were the highest or among the highest yielding varieties in VSAP trials conducted across six sites in the 2012 season, which supports the results of NVT trials. Furthermore, EGA Gregory had the lowest grain protein in all trials compared to LongReach Spitfire , Livingston and Sunvale. Suntop appears to behave similarly to EGA Gregory in terms of both yield and grain protein accumulation, which means that the N removal on a per hectare basis is equivalent to other varieties. LongReach Spitfire  appears unique in the fact that, unlike EGA Gregory, even when it achieves higher yields it is still able to maintain protein concentration, giving it the potential to have a higher protein yield. In the situation where large premiums are paid for protein, EGA Gregory may need specific N management targeting grain protein. However, the limited responses from in-crop N applications reported here highlights the risk associated with the reliability of in-crop rainfall to make use of these applications in the northern region and posses the challenge of how we can reliably supply N throughout the season to adjust for changes in seasonal potential. LongReach Spitfire  on the other hand may need N management with a greater emphasis on maximising yield. With the exception of LongReach Spitfire , there was generally no significant difference between the grain N removal between varieties indicating that achieving protein will be influenced more by other factors, such as residual N, rather than straight variety choice.

 Time of sowing and new varieties 

The autumn break in NSW occurs anywhere between March and June, with the reliability of the break being more inconsistent in northern NSW compared to the south. Wheat varieties available to growers provide the opportunity to plant wheat crops from late March until late June and still have the crop flowering when the risks of frost and heat stress are acceptable. Between mid September to the first week in October is the optimum flowering window for cereal crops at Tamworth to avoid excessive frost risk (>10%) and limit exposure to heat stress later in the season. Trials were conducted at Tamworth to determine the yield and quality of a range of wheat varieties across 3 different sowing times.

What did we do?

There were 18 varieties with varying maturities and agronomic traits used in the trials in 2012 TOS trials for both wheat and barley, including both commercially available lines and advanced breeder lines. These varieties were sown on 3 separate occasions 26^th April, 20^th May and the 20^th June. For the purposes of this paper yield and anthesis dates for 9 and 11 varieties for the wheat and barley TOS trials, respectively, are presented. 

What did we find?

In 2012 there was a significant decline in grain yield for each delay in planting time. On average TOS 1 and 2 both flowered within the optimum flowering window for Tamworth, while TOS 3 flowered 10 days past the optimum window. Surprisingly, Longreach Spitfire, had the highest yields from TOS 1, but was similar to Suntop, Caparoi and Livingston. LongReach Dart had the greater yields than all other varieties except for EGA Gregory, which was similar to Suntop. EGA Gregory had the highest yields of all varieties in the final TOS, this is despite flowering on the 21^st of October. Suntop and Sunguard had similar anthesis dates to EGA Gregory across the 3 planting times. For TOS 1 and 2 LongReach Dart was 17 and 10 days quicker than the average anthesis date, however, despite the earlier anthesis the time taken to reach physical maturity was the same as Longreach Spitfire. For the last TOS, LongReach Dart flowered at a similar time to LongReach Spitfire, and Livingston. The LPB07-0548 line was slightly longer than EGA Gregory in the 2012 trials.

Table 5: Grain yield, yield rank and days to anthesis for 9 wheat varieties at 3 sowing times at Tamworth in 2012. Lsd’s for TOS and variety were 0.41 t/ha and 0.24 t/ha, respectively (P<0.05).

Delaying planting date from the 26^th April to the 20^th May had no significant effect on yield when averaged across 11 barley varieties in 2012. The last TOS however, resulted in a 33% yield loss compared to TOS 2. The first TOS flowered 18 days earlier than the optimum flowering window, while TOS 2 and 3 flower in the optimum window. Oxford and Fairview were the highest yielding varieties from TOS 1, both of which are mid to long season varieties.  Fathom, Grange and IGB1101 also achieved in excess of 6 t/ha from TOS 1, which is interesting given that both Fathom and IGB1101 are quicker varieties. Fathom achieved the highest grain yield for TOS 2, while Commander, Navigator , Grange, Oxford and Hindmarsh all had yields between 6.2 and 6.4 t/ha. From the final TOS Fairview, Fathom, Grange and IGB1101 were the better performing varieties. Oxford and Navigator  are both longer season options, however not as long as Urambie, which had a similar anthesis date. Grange is slightly quicker than Commander while Bass  and Fairview are similar to Commander in their anthesis dates. IGB1101, which is a possible replacement for Hindmarsh , has a similar maturity to Hindmarsh .

Table 6: Grain yield, yield rank and days to anthesis for 11 barley varieties at 3 sowing times at Tamworth in 2012. Lsd’s for TOS and variety were 0.41 t/ha and 0.24 t/ha, respectively (P<0.05).

Time of sowing conclusions

The TOS trials allow us to gauge how new varieties entering the market compare in their maturity and yield to existing variety benchmarks. In the wheat, Suntop provides an alternative to EGA Gregory in the market with similar yields and maturity, while LongReach Dart provides a quick option that is faster than anything else on the market from a main season planting time. Despite the quick time to reach anthesis LongReach Dart does not reach physical maturity any quicker than LongReach Spitfire, which suggests that it has a longer grain filling period. From the barley TOS, Fathom emerged as a high yielding feed variety across all three planting times along with Grange and Fairview. Oxford was a good yielding variety, particularly from the earlier planting. IGB1101 appears to be a viable Hindmarsh  replacement with slightly better yields and similar maturity.  

Acknowledgments

The authors would like to thank all trial cooperators for providing trial sites. Technical assistance provided by Rod Bambach, Jan Hoskins, Patrick Mortell, Stephen Morphett, Jim Perfrement, Rob Pither and Jayne Jenkins are gratefully acknowledged.

Contact details

Matthew Gardner
NSW Department of Primary Industries
Ph: 02 6763 1138
Fx: 02 6761 2222
Email: matthew.gardner@dpi.nsw.gov.au

Reviewed by

Steven Simpfendorfer