Benchmarking crop performance following soil profile re-engineering: four-year field studies in an Arenosol and a Kurosol of Western Australia

ContextSoil constraints, including subsoil acidity, compaction, and low fertility, limit crop productivity and water-use efficiency (WUE) in Western Australia (WA) and around the world. Conventional amelioration offers slow or short-lived benefits. Soil profile re-engineering (SPR), involving deep mixing with amendments to 80 cm depth, may address multiple constraints, but the longevity of its productivity benefits and economic outcomes remain poorly understood.AimThis study assessed the persistence of soil improvements and crop responses to soil re-engineering across four cropping seasons under variable rainfall.MethodsEight treatments, including an untreated control, shallow surface amendments, and four re-engineering approaches, were evaluated in a partially randomised block design on two contrasting soils: an Arenosol and a Kurosol in the central wheatbelt of WA. Measurements included soil physicochemical properties, grain yield, WUE, and N and K uptake.Key resultsAll SPR treatments involving soil loosening and incorporation of lime substantially increased pH _Ca and cation exchange capacity (CEC) and reduced soil strength, while clay addition enhanced volumetric water content, and addition of compost increased soil organic carbon (SOC) throughout the profile. Grain yield increased by up to 432% and WUE by up to 9.8 kg mm⁻¹ relative to the control, whereas shallow incorporation treatments produced no or minimal yield and WUE gains depending on the soil types, amendments, and crop types. Yield responses to SPR were consistent across seasons, crops, and soil types. N and K uptake increased proportionally with yield. Regression tree analysis identified changes in CEC, SOC, and soil strength as the dominant predictors of yield improvement (explaining up to 80.4% of variance) across both soils. Clay addition was the primary driver of yield gains in the Arenosol, whereas increases in pH _Ca were more influential in the Kurosol. Benefits from SPR persisted for at least four cropping seasons and are expected to continue for several years. Conclusions and i mplications Although soil profile re-engineering may not be economically scalable at present, it provides a valuable benchmark for designing targeted, cost-effective amelioration strategies to enhance the resilience and productivity of rainfed cropping system in semi-arid environments in WA.