Potassium nitrate (kno₃) seed priming enhances soybean seed performance

Soybean is a globally important crop, especially in tropical regions, where its high productivity is linked to the adoption of advanced cultivation technologies. Seeds are key to this process, acting as the main vehicle for transferring innovations to the field. However, variability in physiological seed quality can affect uniform seedling establishment and crop yield. In this context, seed priming with potassium nitrate (KNO₃) has been studied as a technique to enhance germination by activating pre-germinative metabolism without root protrusion. KNO₃ acts both as a nutrient and a signaling molecule. This study evaluated the effect of priming with KNO₃ (0%, 1.0%, and 1.5%) on soybean seeds of high, medium, and low physiological quality. Seeds were soaked in KNO₃ solutions for 12 h, and several parameters were analyzed: root protrusion, germination rate, speed of germination, cold tolerance, seedling length, and shoot/root biomass. Results showed that priming was particularly beneficial for low-quality seeds, improving germination, cold tolerance, and biomass. Medium-quality seeds showed reduced germination at 1.5% KNO₃, while high-quality seeds responded positively in root biomass at the same concentration. In general, priming helped reduce physiological differences among seed lots, especially benefiting those with lower initial quality.