Deep Amelioration of Compaction and Acidity Doubled the Water Use Efficiency of Cereal Crops on a Sandy Soil in a Long-term Experiment in a Water-Limited Environment

The co-occurrence of subsoil compaction and acidity commonly decreases the yield and water use efficiency (WUE) of agricultural crops around the world, yet the benefits of the complete amelioration of these constraints on yield and WUE remain unclear. We conducted a long-term field experiment in Western Australia (WA) to evaluate the effects of the complete removal of subsoil compaction and acidity through soil profile reengineering — involving soil removal, replacement, and lime incorporation — on root architecture, yield, and WUE in wheat ( Triticum aestivum L.) and barley ( Hordeum vulgare L.). Treatments included an untreated control, and soil loosening to 0.45 m depth and lime incorporation at three depths combined with loosening (0.45 m). Results showed that the improvements in soil conditions through soil reengineering were maintained for seven years. In the control, the roots of cereal crops were confined to the top 0.2–0.3 m of soil, while soil reengineering tripled the rooting depth and created a more uniform root distribution. The removal of compaction improved wheat root architecture but did not affect barley. These improvements increased yield and WUE up to 3.7-fold, and the benefits occurred in every season. In the best treatment, wheat yield ranged from 945 to 4,164 kg ha⁻¹ and WUE from 16.9 to 33.3 kg mm⁻¹, compared with 252–1,722 kg ha⁻¹ and 6.5–13.0 kg mm⁻¹ in the control. Moreover, the best treatments substantially exceeded the expected yields of crops grown under comparable climatic conditions, based on two independent published datasets from WA and southern Australia. Our findings show that soil reengineering can sustainably improve yield and WUE on coarse-textured sandy soils with multiple subsoil constraints for the long-term in water-limited environments. While this approach may not be directly scalable or economically feasible, it provides a foundation for the development of next-generation tillage machinery capable of achieving scalable soil profile reengineering.