Effect of methods and levels of zinc sulphate application on performance of onion (Allium cepa L.)

Abstract

The present investigation was under taken to identify the ideal method and optimum dosage of zinc sulphate application for enhancing the growth, yield and quality of onion at Regional Horticultural Research and Extension Centre (RHREC), Bengaluru, Karnataka, India during the winter season of 2021-22. The experiment was laid out in randomized complete block design with twelve treatments and three replications. The treatments comprised of control (RDF: 125:75:125 kg ha-1 of N, P2O5 and K2O, respectively + FYM @ 30 t ha-1), three treatments consisted of RDF along with soil application of 2.5, 5.0 and 7.5 kg ha-1 of zinc sulphate at the time of transplanting, another two treatments comprised of RDF along with fertigation of 2.5 and 5.0 kg ha-1 of zinc sulphate in four equal splits weekly from 30 DAT and remaining six treatments consisted of RDF along with foliar spray of 0.25, 0.50 and 0.75 per cent zinc sulphate either as single spray at 30 DAT or two sprays at 20 and 40 DAT. The results obtained have clearly demonstrated that the foliar application of 0.5 per cent zinc sulphate at 20 and 40 DAT along with RDF had produced superior growth attributes (plant height, number of leaves and leaf total chlorophyll content) at all crop growth stages of onion. The same treatment recorded the better yield attributes such as average bulb neck girth (5.02 cm), average fresh and dry bulb weights (113.30 and 15.40 g, respectively) and bulb yield of 77.20 t ha-1. The proportion of A-grade bulbs produced which represents superior bulb development and uniformity was significantly highest (18.51%) while C-grade bulbs which represents the lower-quality category was significantly lowest (20.29%) in the same treatment. The statistically highest TSS content (12.87 0Brix) indicating superior soluble solids accumulation, ascorbic acid content (11.25 mg 100g-1) and antioxidant activity (523.67 μmol g-1) were recorded in fresh bulbs which received the same treatment.