Abstract

                                Field experiments were conducted during rabi season of 2018 andsummer season of 2019 at farmer’s field, western zone of Tamil Naduat Pattiyarkovilpathy, Theethipalayam and Narasipuram villages ofThondamuthur block of Coimbatore district. Totally five treatments comprisingof varied CuSO4 levels (0, 2.5, 5.0, 7.5 & 10.0 kg ha-1) were replicated fourtimes in a randomized block design under irrigated conditions. The resultsshowed that, fresh mean bulb yield of onion in four locations ranged from12.4 to 15.6 t ha-1. The highest mean bulb yield of 15.6 t ha-1 was registeredwith recommended NPK+5 kg CuSO4 ha-1 and the lowest mean bulb yield of12.4 t ha-1 was recorded in NPK control with no CuSO4 addition. Dry MatterProduction ranged from 1065 to 1199 kg ha-1. The highest DMP of 1199 kgha-1 was recorded in the treatment that was applied with NPK+5 kg CuSO4ha-1 and the lowest DMP (1065 kg ha-1) was noticed with NPK control.Concerning copper content in bulb and foliage, it ranged from 6.09 to 12.3and 8.46 to 13.7 mg kg-1 with the location mean of 6.16 to 12.0 mg kg-1and 7.61 to 11.1 mg kg-1, respectively. Copper uptake in bulb and sheathvaried from 7.05 to 18.3 and 6.26 to 11.0 g ha-1 (mean of 8.55 to 12.3 and6.52 to 10.4 g ha-1), respectively with a total uptake of 14.1 to 27.6 g ha-1.In both bulb and foliage, Cu content and uptake, increased with increasingdoses of CuSO4 and the highest Cu content and uptake was registered withthe application of CuSO4 @ 10.0 kg ha-1. Regarding the availability of copperin soil, it ranged from 0.73 to 2.42 mg kg-1 and increasing levels of CuSO4application increased the DTPA Cu status in soil and application of 10.0 kgCuSO4 ha-1 recorded the highest copper availability in soil. Quality parametersviz., TSS, titrable acidity and ascorbic acid varied from 10.25 to 14.08 oBrix,0.28 to 0.61% and 12.9 to 20.1 (100 g-1FW), respectively. Field experimentsconducted to optimize the rates of copper sulfate application to improve theyield and quality of aggregatum onion in four locations at Coimbatore district,showed that, soil application of 5 kg CuSO4 along with recommended NPK@ 60:30:30 kg ha-1 was found optimal for obtaining higher bulb yield (15.6t ha-1) and better quality in aggregatum onion with a BC ratio of 4.63.

Key words : Aggregatum onion; Copper sulphate - optimization; yield; Quality