Combined effects of humic acid and citrus-specific micronutrient formulations on growth and nutrient uptake of pummelo (citrus grandis osbeck.) seedlings

A study was conducted at the ICAR-Indian Institute of Horticultural Research, Bengaluru, to evaluate the combined effects of humic acid and a citrus-specific micronutrient formulation (Arka Citrus Special) on the growth and nutrient content of pummelo seedlings. This research, carried out during 2021-2022, used a factorial completely randomized design with four replications. Two-month-old seedlings were treated with six levels of humic acid (0, 1, 2, 3, 4 and 5 ml per liter) and five levels of micronutrients (0, 0.5, 1.0, 1.5 and 2 g per liter) under glasshouse conditions over four months. Results showed significant improvements in plant height, stem girth, leaf number, biomass, and root traits, with the most substantial growth observed at 2 ml per liter of humic acid and 2 g per liter of micronutrients, applied every 20 days. Increasing humic acid beyond this concentration resulted in decreased growth parameters. These optimal levels also significantly enhanced mineral nutrient concentrations in leaves, stems, and roots, suggesting that 2 ml per liter of humic acid and 2 g per liter of micronutrients optimally increase growth, biomass, and nutrient uptake. This facilitates early planting and improved field establishment of pummelo seedlings, potentially enhancing nursery management practices and seedling vigour for better crop establishment.