Onion (Allium cepa L.) production is susceptible to weed interference due to delayed germination and initial slow crop growth. A scries of trials were conducted during 1991/94 to determine the critical period of weed competition, varietal selection, herbicide evaluation, and the effects of rolling and depth of seeding. The study demonstrated a critical period of weed competition of 0 to 50 days after emergence, ic. the crop must be kept essentially weedfree, and that Assure at seeding depth of 3.75 cm and Dacthal and Prowl (1.25 cm) are the most promising herbicides for var. Grandstand However, in varietal trials var. Special 38 and Grandnoble produced significantly higher yields than Grandstand. Yields of Grandstand were improved significantly in 2 of 3 locations when seed-beds were rolled regardless of seeding depths. NPK(12;12:20) (3)538kg.ha 1 at planting plus sulphate of ammonia(384 kg.ha1) and muriate of potash (234kg.ha ') split application at planting and 6 WAE is recommended. The potential of onions grown under adequate weed-free conditions for periods of up to 60 DAS varied between 39.5 to 55 t.ha '.