Management of fertility and disease must be more exacting when growing on narrow row spacings. When seeding during hot weather, the beds must be kept moist to insure proper germination and to prevent stress on the plants. This means that beds may have to be irrigated several times a day with 0.1 to 0.2 inches of water. Weed Control Weed control is vital to producing high quality onions. Onions compete poorly with weeds, so weeds can drastically reduce yield and quality.
Weeds make the onion crop harder to harvest and can make other pest-control measures less effective.
There are several options for weed control. Cultivation is difficult in onions because of their shallow root system. Cultivate shallowly early in the season but avoid throwing extra soil around the plants. Avoid late cultivation because it will cut roots and break the foliage. Chemical weed control probably offers the most efficient and effective method of control, particularly for large plantings.