Components of test weight of ten varieties of winter wheat grown with two rates of nitrogen fertilizer application

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Abstract
SUMMARY Varietal and environmental factors which influence test weight were investigated in a field trial with ten varieties of winter wheat and two rates of nitrogen fertilizer. Varietal differences in test weight were correlated positively with the protein content of the grain and inversely with grain yield but they were not related to 1000-grain weight or to flour yield. Variation in test weight associated with varietal and environmental effects in protein content was due to differences in the density of the grain, as measured by displacement of xylene. Separation into density grades within a sample by a flotation method showed a similar relationship with protein content. There were also varietal differences in packing efficiency of the grain. In the case of Maris Huntsman a poor packing efficiency was considered to stem from morphological features of the floret and developing grain which lead to characteristic transverse folds in the ventral surface of the mature grain. For wheat grown in the United Kingdom, test weight may provide a useful guide to flour yield for samples of one variety but it is likely to be misleading for comparisons between varieties.