Stolon development in grazed ‘Grasslands Nui’ perennial ryegrass

Turf was taken from grazed ‘Grasslands Nui’ perennial ryegrass ( Lolium perenne L.) + ‘Grasslands Huia’ white clover ( Trifolium repens L.) pastures to count ryegrass stolons and locate tillers on stolon nodes. In the first experiment, eight grazing treatments were sampled in summer. Ryegrass tiller density was 6985 tillers/m 2 , stolon density 2420 stolons/m 2 , and 79% of ryegrass tillers were attached to stolons. Grazing treatments did not significantly influence the density of stolons, but more intensive grazing during late spring and early summer reduced the number of internodes on stolons. In a second experiment, turf was taken during spring and summer to study the timing of stolon formation. Stolon density was low in early spring (40 stolons/m 2 , increased during culm elongation (450 stolons/m 2 at inflorescence emergence), then increased markedly after grazing killed reproductive tillers (2000 stolons/m 2 in summer). Stolons developed when basal internodes of vegetative tillers elongated and roots formed on buried nodes (75%), or when subsidiary tillers and roots developed on buried nodes of decapitated culms (23070). Rooting of aerial tillers appeared to be relatively unimportant for stolon formation. It was concluded that ryegrass stolon formation in grazed swards occurred after earthworm casting and animal treading in winter had partially covered tillers. These covered tillers elongated in spring until the apical meristem was near the soil surface, and subsequent root formation resulted in stolon production.