Shiraz University Iran Agricultural Research 1013-9885 45 2 2026 07 01 Chitosan and humic acid as biostimulant seed coatings enhance germination and seedling growth in two forage pea varieties (Pisum sativum var. arvense (L.)) under drought stress 1 11 8675 10.22099/iar.2026.55662.1740 EN Elham Bahrabadi Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, I. R. Iran Yahya Emam Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, I. R. Iran Reza Tavakkol Afshari Department of Agrotechnology, School of Agriculture, Ferdowsi University of Mashhad, Mashhad, I. R. Iran Journal Article 2026 02 12 Forage pea is an important legume used as livestock feed; however, environmental stresses, particularly drought, significantly affect its germination and seedling growth. Seed coating technology is an effective strategy for enhancing seed germination and seedling growth under drought conditions. This study was conducted to evaluate the potential of seed coating with chitosan (0.1%, 0.15%, 0.2%, and 0.3%) and humic acid (16, 17, 18, and 19 g kg^-1 seeds) under drought stress (0, -3, -6, and -9 bar) in two forage pea varieties (Pionir and Arda). Evaluations considered final germination percentage, mean germination rate, and shoot and root length. Overall, the Pionir variety showed higher final germination percentage, mean germination rate, and shoot and root length than the Arda variety under both normal and drought stress conditions. In the Arda variety, significant decreases in the measured traits were observed under -6 bar drought stress. The two cultivars showed significant differences in shoot length, whereas no significant differences were observed in root length The results for the Pionir variety indicated that seed coating with chitosan (0.2%) improved shoot length by 41.95% and root length by 30.15%, whereas humic acid (19 g kg⁻¹ seeds) increased shoot length by 28.79% and root length by 14.03%. Similarly, in the Arda variety, chitosan (0.2%) increased shoot length by 57.44% and root length by 8.07%, while humic acid (19 g kg⁻¹ seeds) improved shoot length by 32.87% and root length by 30.25%. Thus, these biostimulants can enhance forage pea seed germination and seedling growth.  https://iar.shirazu.ac.ir/article_8675_1371f79f0530cd4921daa1ee5ba70808.pdf