Multiple subsoil constraints and unpredictable climatic events are common in southwestern Western Australia (WA), limiting the water-limited yield potential (Yp) of grain crops. Our previous research suggests that soil re-engineering could potentially double grain yield and water use efficiency (WUE) in the short term, particularly in favourable seasons (Azam et al. 2023). However, key questions remain: (i) will these improvements be sustained in the long term, and (ii) if so, can this approach be scaled for widespread adoption by growers? To address these questions, we investigated two long-term experiments over four seasons at Bolgart (deep sand) and Meenar (sandy duplex) in WA. Additionally, we assessed the applicability of soil re-engineering outcomes across multiple sites in WA.

The results from the long-term experiments showed that certain soil re-engineering treatments at least doubled grain yield and WUE on deep sand compared to the control, while the most effective treatment achieved the estimated Yp on both sand and sandy duplex soils. Overall, yield increased by 66% following the removal of subsoil acidity and compaction. On deep sand, the deep incorporation of clay and organic matter significantly enhanced yield and WUE, whereas this effect was not observed on sandy duplex soils. Conversely, the deep placement of additional inorganic nutrients provided significant benefits on sandy duplex soils but not on deep sand. Our findings indicate that these improvements in soil properties persisted for four seasons and are expected to last even longer.

We also successfully implemented several grower-scale experiments using a combination of farming and road implements, eliminating the need for labour-intensive tools previously used in blue-sky experiments. Initial results suggest that subsoil acidity and compaction were immediately mitigated, while soil water-holding capacity improved significantly. Our research demonstrates the potential for developing more resilient sandy soils and achieving Yp consistently at the farm scale.