Hyper Yielding Crops – are there learnings outside of the high rainfall zone?

Take home messages

• The Hyper Yielding Crops (HYC) project is a GRDC national investment which aims to push the economically attainable yield boundaries of wheat, barley and canola across five states.
• Hyper yielding cereal crops cannot be produced with artificial fertiliser alone; rotations which lead to high levels of inherent fertility are essential to underpin high yields and the large N offtakes associated with bigger crop canopies.
• The world record for wheat set in 2020 in New Zealand showed wetter soils (irrigated) improved nitrogen use efficiency and illustrated the importance of good soil nitrogen (N) supply in supporting high yields.
• Disease management is one of the most important management components of growing high yielding cereal crops in seasons that favour higher yield potential.
• Where genetic resistance in a wheat cultivar is not sufficient to delay fungicide decisions until flag leaf emergence (GS37-39), look to target the following three key timings for fungicide intervention; first node GS31, flag leaf emergence GS39 with an optional third application at head emergence GS59.
• Avoiding repeated use of the same fungicide active ingredients, and in the case of the newer Group 11 QoI (strobilurins) and Group 7 SDHIs, where possible, restrict strategies to just one application per season to slow down and help prevent the selection of resistant strains of the fungus.

Hyper Yielding Crops research and adoption

Led by Field Applied Research (FAR) Australia, the Hyper Yielding Crops (HYC) project is a GRDC national investment that commenced 1 April 2020, which aims to push the economically attainable yield boundaries of wheat, barley and canola in those regions with higher yield potential. Hyper Yielding Crops project builds on the success of the GRDC’s four-year HYC project in Tasmania, which demonstrated that it is possible to significantly increase yields through sowing the right cultivars and effective implementation of appropriately tailored management strategies. While the project team is clearly aware that Tasmania is not mainland Australia, it is believed that there are some common threads to the research that could benefit this mainland HYC initiative and for growers in regions that experience high yielding conditions in some seasons.

The first learning is the ability to operate a research centre that can look at all the latest developments in germplasm and agronomy in one location. This has already been established in the first two years of research delivered at FAR Australia’s South Australia Crop Technology Centre (SACTC) Millicent, located in the state’s South East; here winter wheat germplasm such as Anapurna and RGT Accroc wheat cultivars have performed well, mirroring results from Tasmania. The ability to research all the agronomic levers and new germplasm on the same site may not appear unique but when combined with results from other HYC research sites, it can be powerful. The second point is that across Australia, sowing dates are moving forward irrespective of region, and as a consequence, our germplasm requirements are changing. Moving sowing dates forward comes with its challenges, particularly in higher yielding long season scenarios where we need to be mindful of cultivar suitability and phenology and increased disease pressure and lodging risk. As a result, the HYC project is screening both winter and spring germplasm to determine if long season germplasm has high potential in mainland HRZ environments. At the HYC research sites, we are looking to determine if overseas bred material can offer any steps forward in the same way that cultivar RGT Planet (barley) did in 2016. There is a strong focus on nutrition and disease control, since fungicide technology has developed considerably over the last decade, as has the increased risk of fungicide resistance in the pathogens.

As well as the five HYC research sites across the higher yielding regions of New South Wales (NSW), Western Australia (WA), SA, Victoria (Vic) and Tasmania (Tas), the project wants to engage with growers and advisers to scale up the results and create a community network aiming to lift productivity (see details at the end of this paper).

Results from the first year of HYC research trials are currently being harvested and processed at the time of writing, however there are some early learnings and results from the previous project that have applicability in other high rainfall regions when seasonal conditions favour high yields.

Nutrition and rotation for hyper yielding wheat –farming system fertility

The current world record wheat crop produced by Eric and Maxine Watson in New Zealand holds important lessons for us all, even if we don’t farm in a region where 17.39t/ha is possible! The first is that simply applying more and more fertiliser is not the route to achieving big yields. This is clearly seen when one considers the overall N fertiliser input applied to achieve the record yield. A simple look at a commonly used N budget here in Australia makes clear the importance of farming system fertility in achieving big yields of cereals and canola. For example, it is widely assumed that:

• For every tonne/ha of wheat yield the crop needs to be supplied with 40kg N/ha.
• For every tonne/ha of canola yield the crop needs to be supplied with 80kg N/ha.

The key word here is ‘supplied’ rather than ‘applied’. Using 40kg N/ha to achieve a crop of 17.39t/ha, the world record wheat crop would have required (from soil reserves and fertiliser) approximately 695kg N/ha based on our commonly used N budgets. In fact, the record crop received a total of 301kg N/ha applied N, begging the question where did the other 394kg N/ha come from? Improved nitrogen use efficiency (NUE) with irrigation clearly reduces the overall N requirement, but the reality was that a wheat crop yielding 17.39t/ha removed more N in the grain alone than could be accounted for with the N applied. Once the N in the crop canopy (straw and chaff) rather than the grain is considered, it is clear that the contribution of soil N supply as opposed to N fertiliser is vitally important in achieving big crops. The world record crop did not have a dry matter sample taken at harvest but with a typical harvest index of 55% the final harvest biomass is likely to have been in the region of nearly 32t/ha. If it’s assumed that 25% N at harvest is in the straw and chaff rather than the grain, total crop N removal assuming all stubble was removed from the paddock (baled or burnt) would have been closer to 420kg N/ha.

Nitrogen input and offtake calculation assumptions – 2020 NZ World Record

• Yield – 17.398t/ha with a grain protein content of 10.26% equivalent to grain N content of 1.8% N.

Offtakes

• N removed in grain = 17,398kg/ha at 1.8% N = 313 kg N/ha in grain*.
• In the crop canopy at harvest, if it is assumed that on average 75% of the N is in the harvested grain, there would be an additional 25% N content in the straw and chaff, therefore in total 313 kg N/ha (grain) x 1.333 = 417kg N/ha removed in crop (grain and straw).

N inputs

• The crop received 301kg/ha N (Flofert liquid Urea 18% N).
• Soil mineral N reserve (0-60 cm) at start of spring 46kg N/ha.
• Soil mineralisation under irrigation assumed to make up the residual 70kg N/ha.

(*Assumptions based on grain at 15% moisture).

At the beginning of spring 46kg N/ha was available in the soil based on a 0-60cm soil mineral N test with the assumption that the residual 70kg N/ha was supplied by the soil through soil mineralisation.

Therefore, while achieving the world record required more fertiliser than that typically applied to crops in lower yielding scenarios, the record yield was still dependent on the farming system and soil organic matter to supply the N to support such a large yield and crop canopy.

Similar findings have been observed in the GRDC Hyper Yielding Cereal project in Tasmania where high wheat yields were achieved in the absence of excessive N fertiliser applications (Figure 1). The results indicated that high yields were dependent on the fertility of the rotation and farming system. In effect, the soil fertility was being ‘mined’ to produce the high yields, rather than the additional applied fertiliser N in that growing season. In the research conducted from 2016 to 2019, attempting to apply all the N required for a ‘hyper yield’ resulted in failure.

Figure 1. Nitrogen removed at harvest in both grain and total crop (kg/ha) and percentage of applied nitrogen accounted for in the final crop canopy at harvest – Hagley, Tasmania, Irrigated wheat RGT Relay 2019. Previous crop was poppies with a long history of lucerne a decade before.

n.b. * More nitrogen was applied to the crop than the total recovered in the canopy indicating that a proportion of the applied fertiliser N has been lost or left in the soil. Yields expressed at 12.5% moisture and N removal at 0% moisture.

Attempts to apply over 250kg N/ha as urea fertiliser have been unsuccessful in generating the highest yields in the Tasmanian project. In fact, since 2016 in the Tasmanian trial work optimum applied fertiliser N levels have rarely exceeded 200kg N/ha for the highest yielding crops, even though the crop canopies that these yields are dependent on are observed to remove far more than 250 – 370kg N at harvest.

In HYC nutrition trials just harvested in southern Victoria, attempts to push yields with N applications above 150kg N/ha have led to an increase in grain protein but not yield (Table 1). Again, N recovered in the grain would indicate that more N has been removed (grain and straw) than the crop would respond to in terms of applied N and its effect on yield.

Table 1. Detailed treatment list, grain yield (t/ha), % site mean and grain quality, protein (%), test weight (kg/HL) & screenings (%). Cv RGT Accroc, Gnarwarre, Victoria (HRZ region)

n.b. 22kg/ha of phosphorus applied to all treatments.

GSR - (April-November) 479mm (29mm above the long-term average).

Organic carbon 0 -10cm – 2.37%

An analysis of NIAB TAG trials on wheat from the UK suggested that high yielding crops were produced in paddock scenarios where if the crop in that paddock had been farmed with no nitrogen fertiliser it would have still produced a good yield. This was put forward to explain ‘why the additional amounts of N required for very high yields in field trials is less than would logically be expected’ (NIAB TAG 2018).

Nitrogen deficiency remains the single biggest factor contributing to the sizeable exploitable yield gap in Australian wheat production (Hochman and Horan 2018) yet applying more N has not necessarily removed this constraint even in leading farmers and favourable seasons (van Rees et al. 2014). Clearly, the fertility of farming systems and soil organic matter contents are lower in Australia than in the UK, however the HYC results show the fertility of the whole farming system is a key component to achieving high yields.

Disease management protects high yield potential

Disease management is one of the most important components of growing high yielding cereal crops in seasons with high yield potential. This is primarily a result of the growing season being typically longer, wetter and more disease prone than normal.

In HYC research in wheat it was found that three key timings for fungicide intervention were essential to protect the upper leaves of the canopy, capture the highest yields, and provide the highest economic returns; these were first node growth stage (GS) 31, flag leaf emergence GS39 and head emergence GS59. In barley two timings were essential; GS31 and awn tipping GS49. The introduction of new fungicides over the last five years has lifted our ability to secure a greater proportion of our yield potential in wet seasons conducive to foliar diseases.

Early harvested results in 2020 are already showing this in HYC. This also comes with a responsibility to protect our fungicides from the development of fungicide resistance and reduced sensitivity. One of the key measures we can adopt to slow down the development of fungicide resistance is to reduce the number of fungicide applications.

In HYC 2020 research trials, the objective has been to examine whether newer resistant or tolerant cultivars suitable for high yielding regions might allow us to delay fungicide intervention, and therefore, use less fungicide. If a cultivar has sufficient genetic resistance to suppress disease development it may be possible to delay fungicide application until flag leaf emergence. This will have two primary benefits; firstly, it will allow a much better appraisal of whether the seasonal conditions had the potential to support fungicide expenditure, and secondly, it may mean that a fungicide could be applied to all of the upper canopy leaves at the same time. In those seasons with a dry spring, it means the flag leaf spray expenditure is cut back or removed altogether. However, the industry requires robust genetic resistance in our high yielding cultivars to make this a reality.

Results processed so far in HYC research in southern NSW (Table 2) and southern Victoria (Table 3) not only show the significant influence of disease management, but also the large differences in genetic resistance to disease. In a season with high yield potential and high disease pressure all cultivars produced a significant yield response to fungicide, but where cultivars had greater genetic resistance there was no additional benefit for the extra units of fungicide applied (where the flag leaf spray was based on a full rate azoxystrobin/epoxiconazole mixture (Radial® 840 ml/ha).

Table 2. Influence of fungicide strategy and cultivar on grain yield (t/ha) – HYC Wallendbeen, NSW.

*Scepter was unaffected by wheat powdery mildew at this site. Winter – winter wheat, Facultative – facultative wheat, Spring – spring wheat. Yield figures followed by the same letter are not considered to be statistically different (p=0.05). Plot yields: To compensate for edge effect a full row width (22.5cm) has been added to either side of the plot area (equal to plot centre to plot centre measurement in this case). All provisional results have been analysed through ARM software with further analysis when the final results are released.

Table 3. Influence of fungicide strategy and cultivar on grain yield (t/ha) – HYC Gnarwarre, Vic.

Winter – winter wheat, Facultative – facultative wheat, Spring – spring wheat. Yield figures followed by the same letter are not considered to be statistically different (p=0.05). Plot yields: To compensate for edge effect a full row width (22.5cm) has been added to either side of the plot area (equal to plot centre to plot centre measurement in this case). All provisional results have been analysed through ARM software with further analysis when the final results are released.

Where susceptible cultivars require early fungicide application (e.g., early in stem elongation), it’s imperative to adhere to sound practices to avoid the development of fungicide resistance. These include avoiding repeated use of the same active ingredients, and in the case of the newer Group 11 QoI (strobilurins) and Group 7 SDHIs, restricting fungicide strategies to just one application per season to slow down and prevent the selection of resistant strains.

Interested in hyper yielding crops?

If you are interested in getting involved in the project in south east SA then please get in touch with Jen Lillecrapp, your regional HYC Project Officer (Jen Lillecrapp jen@brackenlea.com).

Acknowledgement

The research undertaken as part of these projects is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. FAR Australia gratefully acknowledges the support of all of its research and extension partners in the Hyper Yielding Crops project. These are CSIRO, the Department of Primary Industries and Regional Development (DPIRD) in WA, SA Research and Development Institute (SARDI), Brill Ag, Southern Farming Systems (SFS), Techcrop, the Centre for eResearch and Digital Innovation (CeRDI) at Federation University Australia, MacKillop Farm Management Group (MFMG), Riverine Plains Inc and Stirling to Coast Farmers.

Contact details

Nick Poole
Shed 2/63 Holder Rd, Bannockburn, Victoria 3331
03 5265 1290; 0499 888 066
nick.poole@faraustralia.com.au

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