Evaluating Biostimulant Products for Wheat Production in Weathered Soils and Dry Environments

ABSTRACT The need to reduce reliance on synthetic fertilisers has intensified interest in biostimulants and organic amendments as sustainable alternatives in cereal production. This study assessed the performance of three commercially available biostimulants in wheat ( Triticum aestivum ) across three environments: controlled conditions, an irrigated urban field and a rainfed agricultural field under the challenging conditions of south‐western Western Australia (WA), characterised by hot, dry growing seasons in summer and highly weathered soils. Grain yield, total protein content and nitrogen use efficiency (NUE) were measured at harvest. Across all three growing conditions, the selected biostimulants did not significantly improve yield or protein relative to synthetic fertiliser, with several biostimulant treatments performing below that of conventional N inputs. Although higher NUE was observed under reduced‐N biostimulant treatments, this may reflect low nutrient inputs rather than improved N uptake or utilisation. These findings highlight that biostimulant efficacy must be rigorously evaluated across a gradient of growing conditions to determine their suitability for practical application. Many products are not systematically tested from controlled to field environments, yet such staged assessment is essential to identify solutions capable of supporting sustainable wheat production under increasingly heat‐ and nutrient‐stressed agroecosystems worldwide.