Abstract
<title>Abstract</title> <p> Background and aims Root development is critical for crop adaptation to water-limited environments, yet canola responses to the simultaneous alleviation of multiple soil constraints remain poorly understood. This study investigated whether soil re-engineering could improve root-zone functionality, resource acquisition and crop productivity in a constrained duplex soil. Methods Using minirhizotron imaging and physiocochemical assays, we investigated whether soil re-engineering to 80 cm depth could transform root-zone functionality and enhance resource acquisition canola performance. Treatments comprised a control (T1), deep loosening with lime incorporation (T2), and deep loosening with lime, clay and compost incorporation (T3). Results Soil re-engineering increased soil pH <sub>Ca</sub> from 4.37 to 5.40, while reducing exchangeable aluminium from 17.5 to 1.30 mg kg⁻¹ and soil strength from 2.62 to 0.87 MPa across the 0–80 cm profile. Total root length increased by 106%, and rooting depth doubled from 40 to 80 cm. Consequently, stored soil water extraction increased by 35–45 mm, N, P, K and S uptake by 114%, 228%, 142% and 129%, biomass production by 56%, and grain yield by 48%. Although T2 developed the largest root system, T3 achieved the highest grain yield, demonstrating that crop performance depended on root-zone functionality rather than root size alone. Conclusions Simultaneous alleviation of multiple soil constraints transformed the rooting environment, promoting deeper rooting, greater water and nutrient acquisition, and substantially improved canola productivity. These findings demonstrate that improving root-zone functionality, rather than simply increasing root size, is fundamental to enhancing crop performance in constrained soils. </p>