Project Background

Sandy soils across the Facey Group region often constrain water retention, nutrient availability, and overall crop performance. Soil amelioration practices such as deep tillage and clay incorporation are increasingly used to address these limitations, but they involve high costs and variable outcomes. At the same time, nitrogen (N) remains one of the most significant and uncertain input decisions in broadacre cropping, particularly following legume phases that can contribute substantial biological N.

Despite their importance, the interaction between soil amelioration, legume nodulation, and nitrogen availability is not well understood. This creates uncertainty around fertiliser requirements and return on investment, highlighting the need for integrated, system-level research.

Project Summary

This project investigates how soil amelioration and nitrogen (N) management interact to influence crop performance across a lupin–wheat–canola rotation. Delivered as part of the GRDC RiskWi$e initiative, the trial is designed to assess both the short- and medium-term impacts of soil amelioration on nitrogen dynamics and fertiliser requirements.

Field experiments compare key soil amelioration practices, including deep tillage and soil mixing, against an untreated control. These treatments are then combined with varying nitrogen application rates to evaluate their effect on nodulation, crop growth, grain yield, and protein.

By maintaining consistent trial strips across multiple seasons, the project captures the carryover effects of amelioration and legume nitrogen into subsequent crops. This approach enables a system-level understanding of how soil management and nitrogen decisions interact over time.

2023: Lupins and Nodulation

The first year focused on understanding whether soil amelioration influences lupin nodulation shortly after treatment. Several amelioration methods were compared to an untreated control to assess their effect on nodulation. Results showed no significant differences between treatments, suggesting that nodulation was not limited by soil constraints or improved by amelioration in the first season.

2024: Wheat and Nitrogen Response

Wheat was grown following lupins to evaluate crop response to different nitrogen (N) application rates. High yields were achieved across all N treatments, including those with low or no fertiliser input, highlighting the strong contribution of residual nitrogen from the preceding legume phase.

2025: Canola and Long-Term Soil Impact

Canola was used to assess the longer-term effects of soil amelioration and nitrogen management on crop performance. Soil amelioration had a measurable impact on yield. However, no clear relationship was established between amelioration and nitrogen response under the conditions tested.

The trial site will continue to be monitored without further intervention to assess the longer-term impacts of soil amelioration on crop performance and nitrogen dynamics.