Phosphorus fertilization and yerba mate (Ilex paraguariensis A. St.-Hil.) seed quality

ABSTRACT: Yerba mate seedling production is inefficient and costly, as the seeds have slow and low germination (<20%) and are often embryoless. Because the plant is grown in low-fertility soils, particularly in terms of phosphorus, nutritional deficiencies in the mother trees likely contribute to poor seed quality. Therefore, this study investigates the impact of phosphorus fertilization on the seed quality of yerba mate (Ilex paraguariensis A. St.-Hil.). The experiment was conducted in a seed production area with 1,822 plants, using P2O5 doses of 0, 48, 96, 182, and 288 kg.ha-1. Seed quality was assessed by the 1% tetrazolium test, thousand-seed weight (TSW), and the seed phosphorus content was determined. The results indicated no difference between treatments in seed phosphorus content or 1,000-seed weight, which was 8.0 g. However, seed viability increased with phosphorus application, with the highest quality observed in the 288 kg P2O5 ha-1 treatment. Phosphorus-fertilized mother plants were 2.58 times more likely to produce seeds with embryos. The study demonstrated that phosphorus plays a fundamental role in seed quality, improving viability and embryo presence.