SOURCES OF SCREENINGS IN MALTING BARLEY IN RELATION TO THE PATTERN OF TILLERING

Triumph barley was sown in the field at densities of 125, 250 and 500 plants/m2, and given either no-N, early-N (tillering), or late-N (anthesis) in factorial combination. The treatments produced crops with screening rates varying between 1 and 11 %. Variations in screening rate were better related to both the number of grains/m2 and mean kernel weight than to any other individual variable. High screening rates were observed in crops producing more than 18,000 grains/m2 and where mean kernel weight was less than 45 mg. Screening rate was more related to ear and grain populations than to plant population. Early-N increased the screening rate mainly by producing more higher order tillers. Late­ N decreased the screening rate and increased the kernel weight in all ears with similar magnitude, suggesting the importance of current dry matter production and partitioning to grains during grain filling. Among the ears produced by the crops the mainstem was the least and tiller 3 the most likely to produce screenings. Tillers 1 and 2 had intermediate values. In all ears screenings were generally produced by the terminal spikelets, but in tiller 3, which only survived where early N was applied, screenings were also produced from basal spikelets. Additional Keywords: Sowing density; Nitrogen; Growth potential; DM partitioning; Hordeum vulgare.