Effects of shading and plant density on radiation interception, bulb development and yield of onion (Allium cepa)

The effect of shading was investigated on two early and two late maturing cultivars of onion in two separate experiments conducted at the National Vegetable Research Station, England. Shading reduced the percentage radiation as well as the total radiation intercepted during the bulb growth. The duration of bulb growth was shorter under shading. High plant density gave rise to higher yields while shading caused on appreciable reduction in yields of bulbs. The late maturing cultivars, Express Yellow and Augusta intercepted more radiation and consequently were higher yielding than the early maturing cultivars, Keepwell and Robusta