Agronomist Nick Eyres recently presented innovative strategies for maximizing nitrogen use in wheat farming during the Grains Research and Development Corporation (GRDC) Research Update at Optus Stadium in Perth. His findings address a long-standing challenge for growers: how to enhance nitrogen application efficiency while minimizing costs.
Eyres referred to the ongoing dilemma as the “enigma of nitrogen.” Despite significant investment in nitrogen research, farmers still struggle to determine the optimal methods for nitrogen fertilization. He highlighted the historical context, noting that urea prices soared to $1,500 per tonne just a few years ago. This spike prompted local agricultural groups, including the Yuna Farm Improvement Group and the Council of Grain Growers Organisation, to collaborate with researchers to explore more effective nitrogen application techniques.
In his presentation, Eyres discussed research led by Geoff Anderson, which examined nitrogen flow in legume-wheat rotations on sandy soils in the Central Midlands region. The research, spanning over 30 years, revealed a phenomenon known as “seasonal asynchrony.” This occurs when soils produce excess mineral nitrogen early in the growing season, coinciding with lower plant demand, leading to nitrogen loss through leaching when demand peaks later.
“The implications are significant. These inefficiencies stem from systemic seasonal and climatic mismatches in nitrogen supply and demand,” Eyres explained. “Understanding these principles is critical for growers aiming to enhance their yields.”
In 2022, the trial involved planting a green-manured legume to create a nitrogen-rich environment for subsequent wheat crops. In the following season, researchers planted wheat at two different seeding rates—75 kilograms and 150 kilograms—with three varying nitrogen rates: 0, 25 units (25N), and 80 units (80N). Early irrigation of 40mm was applied in March to induce some leaching, allowing for the evaluation of nitrogen loss throughout the growing season.
The results from 2023 were promising. Despite receiving less than 200mm of rainfall during the growing season, the low-density seeded plot with an application of 80kg nitrogen achieved yields of just over 4 tonnes per hectare, a significant increase compared to plots without nitrogen. Interestingly, a similar yield was recorded in the high-density seeded plot with only 25kg of nitrogen. In comparison, other trials across the region yielded less than half a tonne, underscoring the effectiveness of Eyres’ approach.
The following year, 2024, saw increased rainfall, leading to a clearer nitrogen response in the low-density plots. Wheat yields reached nearly 4 tonnes per hectare with 25N and approached 5 tonnes per hectare with 80N. However, in the high-density plots, nitrogen’s impact remained ambiguous, with yields for both nitrogen rates hovering around 5.5 tonnes per hectare.
In 2025, the trend continued, as the low-density plots showed that higher nitrogen applications correlated with increased yields. Notably, the highest yields, nearly 8 tonnes per hectare, were found in both low and high-density plots with 80N applications. Eyres attributed this success partly to widespread soil amelioration techniques implemented in the region, which addressed issues such as compaction and acidity.
“More than likely, these results reflect a strong response to amelioration,” Eyres noted. “While we did not specifically focus on these factors in the trial, they are crucial drivers of yield.”
Over the duration of the trial, Eyres observed a consistent nitrogen response across three years, even in high-nitrogen environments. He emphasized that the research validates the notion that increasing nitrogen inputs can significantly enhance yields, particularly at standard seeding rates.
One of the pivotal findings was that there were no statistical differences in yields between applying 25N or 80N at a seeding rate of 150 kilograms per hectare. “We achieved maximum yields over three years with wheat planted at industry standards alongside varying nitrogen levels,” Eyres stated. “Increasing the sowing rate in this environment has improved recovery, maximizing the legacy returns on high-nitrogen legumes.”
Additionally, the economic analysis of these practices revealed promising returns on investment. Eyres stated that applying 25N at a seeding rate of 75 kilograms could yield an estimated return of $6.90 for every dollar spent on nitrogen. However, while higher nitrogen inputs at the same seeding rate reduced ROI to $4.56, doubling the seeding rate to 150 kilograms with 25N could potentially achieve an ROI of $14.41. Conversely, pairing high nitrogen inputs with double seeding rates brought ROI back down to around $4.
These insights from Eyres offer valuable guidance for growers seeking to optimize nitrogen use and enhance overall yields in wheat production, a critical aspect of agricultural sustainability and profitability.
