Yaseer Suhaimi, M. and Siti Norzahidah, Z. A.
Abstract
This study examined the impact of varying concentrations of indole-3-acetic acid (IAA), a plant growth regulator, on the growth, yield, and quality of sweet potato (Ipomoea batatas [L.] Lam.) under conventional soil planting. Field experiments were conducted at the MARDI Serdang using a randomised complete block design with four treatments (0, 3, 5 and 7 ppm IAA concentration) and five replications across 20 plots. Sweet potato cv. Beni Hanuka was propagated via 30-cm stem cuttings, and the application of IAA was performed as a foliar spray at 21 days after planting. Notably, the 5 ppm concentration (T3) resulted in the highest tuber yield per plot (76.5 kg) and HI (0.53), suggesting improved biomass partitioning toward the storage organs. The 5 ppm treatment enhanced TSS (12.6 °Brix) and produced the highest tuber count (6 tubers per plant) with superior tuber length compared to the other treatments. These results suggest that a moderate IAA concentration optimises both yield and quality by improving root differentiation, photosynthetic efficiency, and assimilate allocation. Overall, the study indicated that a 5 ppm IAA concentration is optimal for sweet potato cultivation, balancing the promotion of storage root development with improved physiological and yield traits.
Keywords: sweet potato, tuber, booster fertiliser, nutrient, yield