Crop response to different soil ameliorants varies with soil type within a paddock

Abstract Background and Aims Subsoil constraints are a widespread limitation to agricultural production in southern Australia, reducing rooting depth and access to water and nutrient resources. The addition of organic amendments and gypsum to dispersive soils has been shown to enhance soil structure and crop nutrition, with potential to significantly increase crop yields. The spatial variation of soil types and constraints within paddocks necessitates zone-specific amelioration strategies that are more cost-effective. Methods Intact soil columns were collected from two distinct soil zones of a single paddock to explore the variation in crop response to several traditional and novel ameliorants under controlled conditions. Ameliorants were incorporated at a depth of 15—30 cm, prior to planting wheat ( Triticum aestivum L. cv. Mace). Resulting changes in physicochemical soil properties and yield components were then quantified. Results The performance of amendments on soil properties and plant productivity depended on the soil zone. In Soil Zone 1, combinations of organic amendments and selected biochar products increased root growth into the dispersive subsoil, and increased yields by up to 55% relative to the control. In contrast, although all amendment combinations reduced dispersion in Soil Zone 2, no benefits to crop growth or grain yield were observed. Conclusions These findings highlight that the agronomic effectiveness of soil amelioration depends strongly on underlying soil characteristics. Tailored interventions that account for within-paddock soil variability are essential for maximising crop response and ensuring the economic viability of amelioration in heterogeneous landscapes.