Key Messages:

• Crop rotation has a major impact on nitrogen response.
  Previous crops, particularly legumes, significantly influence nitrogen availability and crop performance in the following season.
• Higher nitrogen rates do not guarantee higher yield or profitability.
  In some cases, increased nitrogen inputs resulted in limited or no return, highlighting the economic risk of high-input strategies.
• Seasonal conditions, particularly rainfall, drive nitrogen response.
  Water availability remains the primary limiting factor, affecting both yield potential and nitrogen-use efficiency.

Project Background:

Nitrogen management is one of the most challenging decisions in broadacre cropping systems. It represents a major input cost, and its return on investment is highly variable due to seasonal uncertainty, particularly rainfall.

In Western Australia, sandy soils and low water-holding capacity increase the risk of nitrogen losses through leaching and volatilisation. As a result, growers often take a conservative approach to nitrogen application, which can limit both yield and grain protein, particularly in average to high rainfall seasons where crop potential is higher.

Current nitrogen decision-making is typically focused on a single season, without fully considering how nitrogen and crop rotations may influence performance over multiple years. While alternative approaches have shown promise in other regions of Australia, their relevance under WA conditions remains uncertain.

This project aims to address these challenges by improving the understanding of nitrogen requirements and evaluating strategies that better align with the risk and variability of WA farming systems.

Project Summary:

The Nitrogen Banking Project is part of the GRDC RiskWi$e initiative, a national program led by CSIRO (2023–2028) aimed at improving risk-reward outcomes in grain production systems.

In Western Australia, nitrogen decisions are particularly challenging due to seasonal variability and sandy soils. This project focuses on testing nitrogen management strategies within realistic farming systems to better understand how decisions made in one season affect both current and future crop performance.

Field trials led by Facey Group compare different crop rotations and nitrogen fertiliser strategies across multiple seasons. Treatments include varying nitrogen rates and application approaches applied to sequences of crops such as cereals and legumes. The aim is to evaluate how these strategies influence grain yield, quality, profitability, and nitrogen dynamics over time.

A key focus of the project is to assess whether nitrogen applied in one season can provide benefits in subsequent crops (“N banking”), and how this interacts with crop rotation. By taking a multi-year systems approach, the project seeks to provide practical insights to help WA growers make more informed and resilient nitrogen decisions.