Evolving insights from the Soil Water Repellence Project
By Kate Parker & Simon Kruger, WMG
The GRDC-funded Soil Water Repellence Project has continued into its second year, expanding on more than a decade of West Midlands Group (WMG) research into soil amelioration and non-wetting sands. The project is exploring how different approaches perform across sand, sandy duplex, and gravel soils in the West Midlands region, with trial sites established at Dandaragan, Gillingarra and Moora.
Using a participatory action research approach, the project is working closely with local growers to track how amelioration influences soil water repellence, structure, water infiltration, and crop performance over time, and to better understand the practical realities that shape those results.
Shifting Performance Over Time
The 2025 season has provided valuable insight into how amelioration effects evolve beyond the first year. At Dandaragan, where treatments were applied in 2024, both the Plozza Plough and Nufab Rip/Delve (double pass) are now showing clearer benefits. Penetrometer readings indicate that treated plots continue to maintain lower soil strength and allow roots to penetrate more deeply than controls, in some cases reaching over 400mm before encountering resistance.
Interestingly, this represents a shift from the first year, when more moderate treatments (such as single-pass or shallower working systems) performed better. As soils have reconsolidated, the initially more aggressive treatments appear to have stabilised, improving both seedbed uniformity and subsoil structure. The finding reinforces the importance of multi-year monitoring, as early establishment benefits do not always predict long-term soil improvement.
At the new Gillingarra site, this season has demonstrated the importance of adapting management to paddock variability. The site features particularly variable sand-over-gravel and gravel soils, deliberately chosen by the host grower to test how different amelioration systems perform under challenging conditions.
The work has highlighted that amelioration is not simply about choosing the right machine, but about planning for what follows. Post-amelioration, the soil was noticeably looser and more “fluffy” than expected, which complicated seeding depth control and affected early establishment. The experience underscored that each amelioration pass changes the physical behaviour of the soil, requiring adjustments in how seeding, nutrition, and weed management are approached.
Although no significant differences in GS30 biomass have been detected statistically, field observations and penetrometer data suggest that treated plots still offered deeper root penetration and greater soil loosening than the controls. The process has provided the host grower with valuable first-hand experience to refine future amelioration programs, including factoring in seeding depth, soil reconsolidation time, and potential weed seedbank activation.
The Moora site, hosted by local grower John Minty, was the focus of the WMG & Summit Crop Walk earlier this season. The event, held in collaboration with Summit Fertilizers, drew a strong turnout from regional growers keen to see how nutrient management interacts with soil amelioration.
Discussions centred on how deep ripping and inversion treatments can influence the distribution of nutrients through the profile, particularly potassium and nitrogen, and how this affects crop performance over time. NDVI imagery and Peak biomass data supported these observations, showing more even crop growth and stronger biomass development in ameliorated plots compared with the control. While the trial comes to mature, the late-season contrasts are helping growers visualise how amelioration can complement broader soil fertility strategies.
Across all three sites, field observations remain a vital complement to laboratory results. At Gillingarra, for instance, laboratory testing showed little to no surface repellence, yet on-ground inspections revealed limited water movement in bare soil, with moisture following last year’s furrows. In contrast, areas retaining stubble cover demonstrated more even infiltration, confirming that surface management continues to influence soil wetting behaviour even after physical amelioration.
Looking Ahead
The second year of the Soil Water Repellence Project has reinforced that improving non-wetting soils is a process of refinement rather than a single-step fix. Grower involvement continues to be central to the project’s success, with each site offering unique lessons that extend beyond machinery choice.
Whether it’s managing a looser seedbed post-amelioration, adjusting nutrition strategies, or planning for weed control in disturbed soils, this season’s findings show that success depends on understanding how amelioration reshapes the whole farming system.
Monitoring will continue through 2026, with economic and agronomic analyses to be completed once the full dataset is available. The insights already emerging are helping local growers and advisers take a more informed, system-wide approach to tackling soil water repellence across the region’s variable landscapes.
