Impact of Foliar Application of Humic Acid, Manganese Sulphate and Zinc Sulphate on Physiological Responses and Productivity of Potato cv. Lady Rosetta

Abstract

A field experiment was conducted during 2025–26 at the Vegetable Research Farm, Department of Horticulture, Guru Kashi University, Talwandi Sabo, Bathinda, Punjab, India, to evaluate the effects of foliar application of humic acid, manganese sulphate and zinc sulphate on growth, yield and tuber quality of potato cv. Lady Rosetta. The experiment comprised nine treatments, including an untreated control; humic acid, MnSO₄ and ZnSO₄, each at 500 and 1000 ppm; and their combined applications at the same concentrations. The treatments were arranged in a randomised complete block design with three replications. Foliar sprays were applied twice, at 30 and 60 days after planting. Observations were recorded for plant height, number of compound leaves and leaf area index at 100 days after planting, total number of tubers per plant, average tuber weight, yield per plot, dry matter content, specific gravity and starch content. Analysis of variance revealed significant treatment effects for most traits at p < 0.01, whereas specific gravity was significant at p < 0.05. Among the treatments, T8, consisting of humic acid + MnSO₄ + ZnSO₄ at 1000 ppm each, recorded the highest plant height (87.90 cm), number of compound leaves (63.20), leaf area index (3.59), tubers per plant (9.86), average tuber weight (86.10 g), yield per plot (9.10 kg), dry matter content (24.60%), specific gravity (1.093 g cm⁻³) and starch content (17.68%). These values were higher than those of the control, which recorded 77.41 cm plant height, 47.50 compound leaves, 1.90 leaf area index, 5.97 tubers per plant, 51.52 g average tuber weight, 4.21 kg yield per plot, 16.40% dry matter, 1.001 g cm⁻³ specific gravity and 13.36% starch content. Under the conditions of the present experiment, combined foliar application of humic acid, MnSO₄ and ZnSO₄ at 1000 ppm each showed the greatest improvement in potato productivity and processing-related quality traits.