ABSTRACT
Summary Trials in 1979 and 1980 evaluated the effect of autumn and spring defoliations on fertile apex removal, tiller survival, seedyield components, and seed and forage yield in two amenity- and one agricultural-type perennial ryegrasses (Lolium perenne), established in the autumn. Methods (reciprocating mower or sheep), height (3-5 cm or 6-8 cm) of defoliation, and the addition of supplementary nitrogen (N) after defoliation were evaluated in the variety Royal in 1980. In both years and all varieties, autumn defoliation had no significant effect on seed yield. With the exception of Royal in 1980, seed yields were reduced by cutting, if it was carried out after spikelet initiation, due to an increase in apex removal, particularly in autumn-emerged tillers. In Royal in 1980, survival of spring-emerged tillers as mature ears at final harvest was increased by defoliation at floret initiation, and this increase compensated for tiller loss. Seed-yield reductions were accompanied by decreases in all yield components except 1,000-seed weight in both years and seeds/spikelet in 1980. 258Supplementary N failed to compensate for yield loss, but cutting high (6-8 cm) at floret initiation produced 1.2 tons(t)/ha of dry matter with reduced apical loss. Defoliation in autumn-established crops is unnecessary. However, growers with forage requirements may safely defoliate up to spikelet initiation and obtain approximately 2 t/ha of dry matter from these varieties.
