Boron Seed Treatment via Film Coating and Pelleting Mitigates Deficiency Symptoms and Boosts Curd Yield in Cauliflower Under Boron-Deficient Management

Boron (B) is essential for cell wall integrity and meristematic activity in cauliflower (Brassica oleracea var. botrytis). Still, the narrow range between deficiency and toxicity limits soil and foliar fertilization, and seed-applied B remains unexplored. This study establishes the conceptual novelty of boron seed treatment as a targeted preventive tool to safeguard cauliflower performance under boron-deficient soil conditions or management failures. This study evaluated a boron–polyol complex applied via film coating and pelleting to cauliflower seeds, assessing physiological quality, seedling development, and agronomic performance across five B doses (0.5–4.5 g B kg−1) in the laboratory and nursery, and two doses (0.5 and 4.5 g B kg−1) under two fertilization managements in an 8 L pot greenhouse experiment. Boron sharply reduced laboratory germination as the dose increased, falling below the commercial minimum (80%) beyond 0.5 g B kg−1, while seedling emergence in substrate remained largely unaffected (≥94% in most treatments). In the greenhouse trial, without soil or foliar boron, untreated seeds resulted in 62.5% of plants with deficiency symptoms and the lowest commercial yield (3.5 t ha−1); boron seed treatment reduced deficiency incidence and increased commercial yield in three of the four seed treatments, with gains of up to 145.7% relative to untreated seeds. Film coating at 0.5 g B kg−1 seed is recommended as the only dose preserving seed physiological quality for commercialization while increasing commercial yield by 125.7%, showing promise as a low-cost strategy. Conceptually, this work proves that B seed treatment acts as a vital technological safety net in B-restricted areas, drastically reducing deficiency symptoms and protecting yield when standard soil or foliar supply is inadequate.