Abstract
Subsoil acidity and compaction commonly hinder the water use efficiency (WUE) of agricultural crops around the world. Over six years, a field experiment was conducted in south-western Western Australia (s-w WA) to examine the effects of soil re-engineering (loosening and lime incorporation) on the root architecture, yield, and WUE of wheat and barley. Treatments included an untreated control, soil loosening to a depth of 0.45 m and lime incorporation at three depths combined with loosening (0.45 m). Loosening reduced subsoil strength, while liming quickly decreased acidity, which was maintained for six years. In the control plots, roots were confined to the top 0.3 m of soil. Loosening alone significantly enhanced wheat root architecture but had no effect on barley. However, loosening with liming tripled the rooting depth and density for both crops, creating a more uniform root distribution. Loosening with lime incorporation to 0.45 m depth significantly boosted yield and WUE by up to 3.7-fold. Crop yields in re-engineered plots often met or exceeded two of the three yield frontiers (estimated yield potential from models applicable to s-w WA). These findings suggest that strategic deep tillage and liming can sustainably improve WUE in water-limited environments through better soil management.