Effects of waterlogging at different stages of development on the growth and yield of winter oilseed rape (Brassica napus L.)

Oilseed rape, growing in a sandy loam soil in lysimeters, was subjected to waterlogging to the soil surface at different stages of growth. Brief periods of waterlogging in December and January (10 days) or in May (10 days) resulted in slightly shorter plants but hardly affected yield. Waterlogging in December/January for 6 weeks in cold (1–2°C) weather, slightly restricted leaf development and delayed flowering, but yield was unaffected. At the end of waterlogging for a similar duration between January and March (when the mean temperature was about 6°C), the height and leaf area of the plants was approximately halved, the number of senescent leaves was almost doubled and flowering was accelerated; at harvest in July these plants were 17% shorter and yields of seed, oil and straw were 14, 17 and 23% less, respectively, than for plants in freely‐drained soil. During the prolonged waterloggings short fleshy white roots developed slightly below and on the soil surface.