Seed-dressing treatments improve wheat germination and seedling growth under contrasting sowing conditions in a rice–wheat rotation system

Introduction Delayed sowing after rice harvest increasingly compromises wheat establishment and yield formation across rice–wheat rotation regions. Seed dressing may alleviate these constraints, but its effectiveness under humid, late-sown conditions and contrasting soil-cover practices remains insufficiently understood. Methods A two-year, two-factor split-plot field experiment was conducted in Sichuan Province, China. Soil-covered and uncovered surface sowing were assigned to the main plots, and eight seed-dressing regimes were assigned to the subplots. Treatments included Coolas, brassinolide, and Ju Chuan, applied individually or in combination. Germination traits, field emergence, seedling morphology, root architecture, population growth, yield components, and grain yield were evaluated. Results Seed-Dressing Treatments significantly improved seed germination and early stand establishment. Compared with the untreated control (CK), Ju Chuan combined with brassinolide and half-rate Coolas (T J+B+50%C ) increased germination percentage, germination index, and vigor index by 12.89%, 96.12%, and 22.88%, respectively. Coolas alone (T C ) produced the greatest improvement in seedling vigor index, which was 97.69% higher than that of CK. T C also promoted root system development, crop growth rate, and dry matter accumulation. Soil cover shortened field emergence time and increased emergence percentage. Treatment responses varied across developmental stages, with brassinolide alone (T B ) primarily accelerating field emergence. By contrast, T C consistently increased grain yield by 12.5%–21.3% across both growing seasons and sowing methods. Discussion Seed dressing can partially offset late-sowing constraints by improving germination, emergence, root development, stand establishment, and subsequent yield formation. Under the tested field conditions, several seed-dressing treatments showed favorable agronomic responses with soil-covered sowing. However, the study was limited to one cultivar at a single site over two growing seasons. Broader recommendations therefore require validation across multiple cultivars, locations, and agroecological conditions.