Agronomist Nick Eyres has shed light on enhancing wheat yields in Australia’s Mid West region through strategic nitrogen applications. Speaking at the Grains Research and Development Corporation (GRDC) Research Update at Optus Stadium in Perth, Eyres discussed findings from a recent trial aimed at maximizing nitrogen efficiency for local growers.
Eyres referred to what he calls the “enigma of nitrogen,” highlighting the ongoing challenges faced by farmers in efficiently utilizing nitrogen despite decades of research. He recalled a time when the price of urea soared to $1,500 per tonne, prompting the Yuna Farm Improvement Group and the Council of Grain Growers Organisation to collaborate on research efforts to improve nitrogen use in their operations.
A significant part of Eyres’ presentation focused on a study conducted by researcher Geoff Anderson, which examined nitrogen dynamics in sandy soils during legume-wheat rotations. The findings from this 30-year-old research indicated a phenomenon known as “seasonal asynchrony.” This occurs when soils release more mineral nitrogen early in the growing season, a time of low plant demand, resulting in leaching losses when demand increases later.
“The research illustrates how poor efficiencies arise from systemic seasonal and climatic mismatches,” Eyres explained. “Understanding these principles of nitrogen supply and demand can significantly impact growers’ outcomes.”
In 2022, trial participants planted a green-manured legume to create a nitrogen-rich environment for subsequent wheat crops. In 2023, they experimented with two sowing rates—75 kilograms and 150 kilograms—alongside three nitrogen levels: 0, 25 units (25N), and 80 units (80N), with an initial pre-irrigation of 40 mm in early March. Eyres noted that this irrigation intentionally induced a small amount of leaching to track winter nitrogen retention.
Despite receiving less than 200 mm of rainfall during the 2023 growing season, plots that utilized 80 kg of nitrogen achieved yields exceeding 4 tonnes per hectare (t/ha) compared to plots with no nitrogen. Interestingly, high-density seeded plots using just 25 kg also recorded yields of about 4 t/ha. These results outperformed other regional trials, where yields were often below 0.5 t/ha.
In 2024, increased rainfall led to a more pronounced nitrogen response in low-density plots, yielding nearly 4 t/ha with 25N and almost 5 t/ha with 80N. The high-density plots, however, showed no significant difference in nitrogen response, as both 25N and 80N treatments yielded around 5.5 t/ha.
Further trials in 2025 reaffirmed earlier findings—lower density plots saw improved yields with more nitrogen, while high-density plots outperformed lower density ones. The highest yields, approaching 8 t/ha, were recorded in both low and high-density plots that received 80N applications. Eyres attributed part of this success to recent soil amelioration efforts, which addressed subsoil issues like compaction and acidity.
“What we are observing is likely a strong response to amelioration,” Eyres noted. “This is a significant factor in yield improvements, although our focus remains on nitrogen responses.”
Over the three-year study, a clear nitrogen response emerged, even within high-nitrogen environments at standard sowing rates. Eyres emphasized the validity of the 30-year research, stating, “We observed a strong statistical difference in yield responses at the industry standard of 75 kg. While increasing nitrogen inputs maximized yield, the top three yielding treatments did not show statistical differences over the three years.”
A vital conclusion from the research was the lack of statistical difference between applying 25N or 80N at a seeding rate of 150 kg per hectare. Eyres stated, “We can maximize yield across three years by planting wheat at industry practices with high nitrogen, or at double the sowing rate with varying nitrogen levels. Increasing sowing rates enhances recovery in high-nitrogen environments.”
In addition to soil improvement, Eyres highlighted that leaching and access to deep water contributed to the increased yields. He also examined the economic implications of nitrogen application. Applying 25N at a sowing rate of 75 kg per hectare could yield an impressive return of $6.90 for every dollar spent on nitrogen. Conversely, the return with higher nitrogen inputs drops to $4.56. Doubling the seeding rate to 150 kg while applying 25N could potentially achieve a return on investment of $14.41, though this decreases to around $4 when paired with higher nitrogen inputs.
Eyres’ insights provide valuable guidance for growers in the Mid West, emphasizing the importance of understanding nitrogen dynamics and soil health to optimize agricultural productivity. The findings not only present practical strategies for enhancing yields but also demonstrate the long-term benefits of effective nitrogen management in farming.
