SEED PRODUCTION AND ITS COMPONENTS IN BRED POPULATIONS AND CULTIVARS OF WINTER-GREEN SETARIA-SPHACELATA AT 2 LEVELS OF APPLIED NITROGEN-FERTILIZER

Seed production of 2 experimental winter-green varieties of Setaria sp hacelata, EHB (released as cv. Solander) and EHC, was compared with th e winter-green cv. Narok in a split-plot experiment with 2 levels of a pplied nitrogen (N) fertiliser. The experiment continued for 3 years ( 6 harvests), and 3 subharvests at 1-2-week intervals were taken at eac h major harvest to allow for possible phenological differences between varieties. Total numbers of basal tillers, and of basal and aerial ti llers with inflorescences, were counted at each harvest. Ripe and shed ding inflorescences were counted, dried, and threshed by hand, and the seed was sieved and aspirated. The aspirated seed was stored for 6 mo nths, the percentage of spikelets containing caryopses was evaluated, and samples were germinated in petri dishes. Aspirated seed yields of Solander were mostly 50-100% higher than those of Narok, except where yields were generally low, associated with low levels of applied N, an d in later harvests of the experiment. All 3 entries showed a progress ive decrease in seed production over time, and no consistent phenologi cal difference was apparent. The improved seed production of Solander was associated with a markedly higher tiller fertility, lower basal ti ller density, and slightly longer inflorescences. Germination percenta ge of Solander was consistently lower than that of Narok, and it was p ostulated that this was due to a higher level of seed dormancy. Nitrog en fertiliser had a marked positive effect on seed production, inflore scence numbers, tiller fertility, basal tiller density, and infloresce nce length in all populations.