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Wheat, barley and oats were grown in undrained plastic buckets containing soil collected from upper, mid and lower slopes of a valley that was subject to winter waterlogging. Two weeks after planting, the water content for each soil was either maintained at 80 per cent of full water holding capacity or subjected to intermittent or continuous waterlogging for six weeks. In a second experiment, using lowerslope soil only, the same three cereals were subjected to similar waterlogging treatments commencing at two or six weeks after planting or at ear emergence. In this experiment the plants received either no nitrogen fertilizer or 100 kg nitrogen ha-1. Both soil composition and waterlogging had a significant effect on plant yield but the effect of waterlogging was much greater. Waterlogging reduced root growth and penetration, the production of tillers and fertile heads, and delayed ear emergence and plant maturation. Reduction in plant growth rate was measurable within three days from the onset of waterlogging. In the first experiment intermittent and continuous waterlogging reduced vegetative growth yield (mean of three cereals in three soils) by 37 per cent and 55 per cent respectively; and wheat grain yields by 40 per cent and 53 per cent respectively. However, there was no differential effect of the two waterlogging treatments on the grain yield of barley and oats, the mean reduction being 39 per cent for barley and 48 per cent for oats. In the second experiment waterlogging at the earliest growth stage resulted in the greatest reduction in root, herbage and grain yield. Waterlogging at ear emergence killed some tillers and roots and reduced the plants stability at maturity. Grain size was reduced in some treatments. Application of nitrogen fertilizer compensated, either partially or fully, for reduction in grain yield due to waterlogging treatments on all three cereals. Some reasons for yield reduction in the three species and the practical implications of the results are discussed. |
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