NOTE ON THE EFFECTS OF WINTER AND SPRING WATERLOGGING ON GROWTH, CHEMICAL-COMPOSITION AND YIELD OF RAPESEED

in regions where climatic conditions are adequate for rapeseed product ion soils may suffer waterlogging of varying duration. A pot trial was conducted to determine the effects of waterlogging on the growth, nut rient absorption and yield of rapeseed. As the effect of anoxia is kno wn to depend on temperature the study was carried with winter or sprin g floods of 3, 7 or 14 days duration compared with a control without f looding. Seed yield was affected by 3 or more days of waterlogging. Wi nter waterlogging decreased the number of seed per plant, due to fewer branches, siliques and seeds per silique. Spring waterlogging, by con trast, reduced individual seed weight and seed oil content. The uptake of N, P, K and Ca decreased significantly with flooding but that of N a increased with spring waterlogging. Yield decline was greater with w inter than with spring flooding. Temperature during the flooded period was not the only factor determining the effects of waterlogging: the stage of development, when waterlogging occurred, is also an important factor.