Four Years On: Soil Amelioration Still Delivering Plant Establishment Gains

Jul 14,2025 FDF & Soil CRC Long-Term Trials Project, Future Carbon Project, Project Update Article, 2025, Projects, RAD2127, RAD2306,

By Kate Parker, WMG Project Officer

The stacking soil amendments and soil amelioration site at Wathingarra (supported by the Soil CRC, through funding from the Australian Government’s Future Drought Fund) continues to offer valuable insights into the long-term benefits of amelioration and amendment strategies on sandy soils. Now entering its fifth season since the original 2021 amelioration treatments, the site is under wheat once again, with early crop establishment counts reveal some interesting trends.

A recent drone image from the site (Figure 1) shows distinct soil colour and texture changes across treatments. The mouldboard plots stand out most clearly, suggesting significant and lasting soil inversion effects. With closer inspection, the rotary spaded plots are also distinguishable, though less stark. In contrast, the shallow tillage and untreated control strips blend more closely into the surrounding paddock, hinting at their more surface-level impact.

**Figure 1.** Drone image showing colour and texture changes across treatments in 2025 post seeding.

From the establishment data collected this season, it’s evident that deep amelioration treatments like mouldboarding and rotary spading continue to influence crop performance. Both treatments showed higher wheat plant numbers compared to the untreated control, even four years after they were implemented (Figure 2).

**Figure 2.** Plant establishment numbers per metre squared for 2021 Soil amelioration treatments.

When considering the organic and mineral amendments applied in 2022, such as compost, ironman gypsum or biochar and frass (BF), plant numbers trended slightly higher than the unamended strips, although differences were not statistically significant (Figure 3 & 4). This suggests a potential benefit, though perhaps more subtle or variable under this season’s conditions.

**Figure 3.** Plant establishment numbers per metre squared for 2021 soil amendment treatments.

**Figure 4.** Plant establishment numbers per metre squared for 2022 soil amendment treatments

Interestingly, the most informative results emerged from examining the interaction between the 2021 amelioration treatments and the 2022 amendments (Figure 5). In particular:

The untreated NIL control plots had the lowest establishment overall, highlighting the cumulative disadvantage of doing neither amelioration nor amendment.
Among the amendment treatments, the bio-fertiliser (BF) control also lagged behind its ameliorated counterparts.
Both BF and NIL plots that had been mouldboarded showed the highest establishment, reinforcing that the legacy of deep amelioration is still strong when paired with organic inputs or even on its own.

**Figure 5.** Plant establishment numbers per metre squared for 2021 Soil amelioration treatments and 2022 Soil amendment treatments combined.

These patterns underline the idea that soil amelioration can deliver multi-year benefits for crop establishment on challenging sandy soils. While seasonal conditions, rainfall timing, and crop type all play a role, the foundation laid by deep amelioration appears to have a lasting impact. Meanwhile, amendments may offer additional support, though their effects might be more sensitive to the season.

The Wathingarra trial site continues to act as a valuable demonstration of how strategic intervention in soil structure and biology can support better crop performance over multiple years. As we move forward, it’s a good prompt to reflect on what legacy your soil treatments are leaving behind and what you might build on next.