Mechanical in-row weed control in transplanted and direct-sown bulb onions

Different strategies for mechanical in-row weed control were evaluated in direct-sown and transplanted bulb onions (Allium cepa) in terms of in-row weeds, labour requirements for hand weeding and marketable yield. Transplanted onions generally performed much better than direct sown onions. The best strategies in transplanted onions decreased the hand weeding time by 70% and increased marketable yield by 96% compared with the best strategies in direct-sown onions. In transplanted onions, one weed harrowing and three in-row cultivations with torsion weeders reduced in-row weed numbers by 85%, reduced hand weeding time by 73%, and caused no yield reduction compared with the normal strategy of one weed harrowing and ordinary inter-row cultivation. In direct-sown onions, pre-emergence flame weeding and repeated torsion weeding reduced hand weeding time by 40% and caused no yield reduction compared with flame weeding and inter-row cultivation. The effectiveness of in-row cultivation was very dependent on the timing of treatments. Using transplanted onions and in-row weed control is a way to ensure high yields and reduce labour requirements for hand weeding compared with direct-sown onions and inter-row cultivation.