Effect of Tiller Emergence Time in Relation to Autumn and Spring Defoliation on Contribution to Yield in Lolium perenne L.

The contribution to seed yield of tillers emerging at different times in a Lolium perenne L. seed crop which was defoliated by mowing either in autumn only or in autumn and spring (al floret initiation (FI)) was assessed in 1980 at the University of Nouingham, UK. Tillers were marked at monthly intervals from December until May. Autumn-emerged tillers contributed most to final seed yield, and the extent of apical decapitation by mowing at FI was most severe in this group. Autumn defoliation, however, increased the survival and fertility of spring-emerged tillers. The latter had fewer spikelets, and produced seed of lower individual seed weight than autumn-emerged tillers, Plots defoliated at Fl exhibited decreases in these components because of the increased predominance of spring-emerged tillers,