Hyper yielding crops

WHY IS THIS PROJECT IMPORTANT

Following on from the success of Hyper Yielding Cereals (HYC) project in Tasmania, the GRDC Hyper Yielding Crops project commenced nationally during mid-2020, to look at how to maximise crop yields across Australia.

In short: In the Riverine Plains region, we are focusing on maximising the yield potential of wheat and canola through focus farms and innovation groups, while agronomic trials are also helping to unlock crop yield potential. 

Project focus

As part of the project, GRDC Centre of Excellence trial sites were established in Victoria, Tasmania, South Australia, NSW, and Western Australia.  In southern NSW, a Centre of Excellence research site was established at Wallendbeen (near Cootamundra), NSW, chosen because it had a water-limited yield potential of 10 t/ha for cereals and 5 t/ha for canola.

Results presented were from demonstration strips only and were indicative results. 

Project outcomes

Hyper yielding crops – 2022 results

Some of the causes of crops not achieving yield potential in the regions were found to include inherent soil fertility, nitrogen levels, low soil pH in the root zone and variety (winter vs spring wheats).

Key points

• The application of excess levels of nitrogen in 2020 statistically increased the yield of wheat crops in 2021, indicating the previous year’s unused nitrogen can be “banked” for the current year’s crop.
• Lime incorporated to target subsurface acidity in 2021 caused a yield increase compared to areas where lime was not incorporated, with incorporation increasing pH values across the profile.
• Green area index (GAI) can be used to quantify the size of the canopy and assist with nitrogen rate and timing — in 2021, using the GAI to determine the timing and rate of nitrogen application gave a significant yield benefit.

Focus paddock 1: DS Bennett wheat – nitrogen application

Aim

To ascertain the impact of prior year nitrogen application on the yield of the current year’s crop.

Method

DS Bennett wheat was sown with tillage radish at Gerogery, on the 18 March, 2021. Soil nitrogen was measured prior to sowing in 2021, following the application of different rates of nitrogen to canola during the previous year’s strip trials. The paddock was grazed by sheep and cattle for a period of approximately six weeks and stock were removed by the end of July. A total of 210 kg/ha of urea (97 kg N/ha) was applied to the paddock in three applications.

Results and discussion

The yield results of this trial have been analysed (Table 1). The results show a significant yield increase in the wheat crop (2021) from the additional application of nitrogen in the canola crop (2020). An additional 36kgN/ha applied in 2020 to canola compared to Treatment 1, resulted an additional 0.44t/ha in wheat in 2021. With urea priced at $800/t at the time, the investment of $29/ha gave a benefit of $140/ha (wheat price $320/t). An additional 73kgN/ha applied in 2020 to canola compared to Treatment 1, resulted in an additional 0.65t/ha in wheat in 2021. With urea priced at $800/t, the investment of $58/ha gave a benefit of $208/ha (wheat price $320/t).

Table 1 Urea applied 2020 to Hytec Trophy, deep nitrogen and plant counts in Bennett wheat, 2021.

*Yields were statistically analysed using a paired-T test (0.05). Yields with a different letter are statistically different from each other.

2022 updated results: The application of excess levels of nitrogen in 2020 statistically increased the yield of wheat crops in 2021. This indicates the previous year’s unused nitrogen can be “banked” for the current year’s crop.

Conclusion

The data suggests that excess application of nitrogen to a canola crop is still available for the following wheat crop, provided the nitrogen is not lost due to waterlogging or leaching. In this case, soil nitrogen was assessed on 24 May 2021 however the soil test did not reveal the additional nitrogen in the soil. The reason it did not show up in the soil test is unknown. Based on the input and commodity price scenarios of 2020 and 2021 there was an economic return from the previous year’s excess nitrogen. In 2022, fertiliser prices doubled, which makes it less economically viable to apply excess nitrogen. Also the extremely wet conditions increased the potential for the nitrogen to be lost due to waterlogging conditions.

Focus paddock 2: T4510 canola – lime incorporation

Aim

To ascertain the impact of ameliorating sub- surface acidity by incorporating lime.

Method

The paddock was identified by the grower as having potential subsoil acidity constraints. Maps of average crop vigour over a five-year period gave an indication that there were under-performing zones of the paddock (Figure 2). Sites one and two were in the high performing area, three and four in the low performing area with five and six in the medium area. The paddock was extensively soil tested through the Cool Soil Initiative project to gain an understanding of the limiting soil conditions.

A Lemken Rubin 12 was used to incorporate variable rates of lime, rather than applying to the surface, targeting a pH (CaCl2) of 5.8 in the top 10cm. The NSW Department of Primary Industries pH (CaCl2) target of 5.8 ensures there is sufficient lime applied to address acidity in the 0-10cm layer, as well as allowing for some lime to penetrate below 10cm.

The lime was applied at a variable rate with a range of 2.5t/ha to 4.5t/ha and an average application rate of 3.4t/ha. Three areas were left uncultivated, to test the benefit of incorporating lime compared to surface application. Figure 3 illustrates the trial design with the black boxes representing the area where no incorporation took place. The paddock was sown to T4510 canola at Brocklesby, on 30 April 2021. Throughout the 2021 season a total of 162 kg N/ha was applied to the paddock in four applications: 8 kg N/ha at sowing, 37 kg N/ ha on 20 April; 25 kg N/ha on 20 May, 46 kgN/ha on the 9 July and 46kgN/ha on the 9 August 2021. In 2022 the paddock was sown to wheat.

Results and discussion

Comprehensive soil testing was re-done in September 2022; this was postponed from April due to the very wet season. Results indicate that the lime has been incorporated where the treatment was applied. NDVI imagery showed that the small areas of surface applied lime had less dry matter compared to the incorporated areas throughout the 2021 season (surface applied areas are located inside the squares in Figure 5). During 2022, this re-occurred, and while not as obvious, the low yield unincorporated area had visible lower biomass and slower growth in the paddock (Figure 4), although yield maps were unavailable. NDVI imagery from 2022 showed similar results to 2021, with  comparison between years shown in Figure 5.

The soil testing completed in 2022 was analysed in 5cm increments from 0-20cm. Figure 6 shows that where the lime was incorporated, the pH of the profile increased down to 15cm. The pH values at 20cm show little increase, meaning the incorporation did not reach this depth. The incorporation mixed the lime through the profile, removing the stratification of pH. The increase in pH down to 15cm will provide significant benefit to microbial activity and nutrient availability in that zone, while reducing aluminium below toxic levels. Some lime will continue to move down to 20cm depth, especially in the low yielding zone, where there is excess alkalinity in the 5-10cm zone.

Incorporating and applying lime has a long-term benefits as it aids the movement of lime beyond the surface. This demonstration shows that the incorporation has distributed the lime through the profile, increasing pH.

A key learning from this  trial was that the machinery used for incorporation can leave the paddock rough and can cause some issues with sowing and post incorporation. Adjustments have since been made by the grower to put a grader board on the machinery to level and firm up the surface after mixing.

Yield was a stand out benefit for incorporation, and could be visibly seen in the two years following incorporation.

2020 updated results: Lime was incorporated to target the subsurface acidity in 2021 and those areas had an increase in yield compared to areas where the lime was not incorporated. The incorporation increased pH values across the profile.

Focus paddock 3: Raptor canola – nitrogen rates

Aim

To determine the optimum rate of nitrogen for canola.

Method

The paddock was sown to Raptor Canola on 26 April 2021. The demonstration (Figure 5) was designed based on farmer input and included five treatments with varying rates and timings of nitrogen application (Table 1). The green area index (GAI) method trialed by Jon Midwood from TechCrop used soil nitrogen measurements and drone technology to assess the amount nitrogen required. GAI is the ratio of green leaf and stem area to the area of ground on which the crop is growing, with the GAI protocols based on a target of 5t/ha dry matter, which equates to a GAI of 3.5 at early flowering to optimise yield. It takes 50 – 60 kg N/ha to make 1 GAI, therefore 3.5 GAI equates to 175 – 210 kg N/ha. The GAI is measured at set growth stages in the season to enable nitrogen rates to be adjusted to ensure the dry matter target is reached. For further information on how the GAI was calculated and nitrogen rates determined, refer to Riverine Plains Trial Book, 2022.

Results and discussion

A range of nitrogen application rates were tested in consultation with the host farmer, including using GAI to determine application rates. Deep soil nitrogen (0-60cm), taken prior to sowing (5/04/21), showed soil levels between 33 and 54 kg N/ha. Compared to the paddock control, representing farmer practice, the applications of 0 kg N/ha and 37 kg N/ha were significantly lower yielding and less profitable (Table 3). The highest yielding treatment was 221 kg N/ha, however it was less profitable than the GAI treatment (147 kg N/ha, in three applications).

Even though the treatments did not reach the dry matter target of 5t/ha at the start of flowering, favourable seasonal conditions at flowering meant that high yields were still achieved on the GAI and nitrogen-rich treatments.

This paddock was monitored in 2022, to ascertain if the additional nitrogen applied in 2021 had an impact on the wheat crop grown in 2022.

Table 2  Nitrogen treatments - Raptor canola

*Based on urea price of $800/t and canola price of $700/t.

Updated results 2022: The Green Area Index (GAI) can be used to quantify the size of the canopy and may be more accurate with rates and timings of nitrogen application. In 2021, using the GAI to determine the timing and rate of nitrogen application gave a significant yield benefit compared with the farmer application.

The Hyper Yielding Focus paddocks provide an opportunity for farmers and advisors to evaluate hyper yielding research results in a paddock situation.

Conclusion

The Hyper yielding crops project demonstrates the yield possibilities in wheat, canola and barley paddocks. This on-farm demonstration shows that nitrogen is a key driver of high yielding crops. However there is a point where the cost of applying additional inputs becomes uneconomical. In this demonstration, that point was reached with the application of 221 kg N/ha, based on 2021 prices and inputs. This paddock was monitored in 2022 to identify if any of the nitrogen applied in 2021 carried over to benefit the wheat crop in 2022 (results not available at time of publication).

Acknowledgements

The Hyper yielding crops project is a GRDC investment, led by FAR Australia. The Cool Soil Initiative is a partnership between Mars Petcare, Kellogg’s, Manildra Group, Allied Pinnacle, Corson, Charles Sturt University (CSU), and the Food Agility Cooperative Research Centre (CRC), with support from the Sustainable Food Laboratory, Vermont USA.

The authors wish to thank farmer co-operators: The Moll family, the Russell family and the Severin family.

Authors: Kate Coffey, Riverine Plains; Jane McInnes, Riverine Plains; Jon Midwood, TechCrop; Nick Poole, FAR Australia; Cassandra Schefe, AgriSci Pty Ltd.