Effect of early spring grazing frequency on the reproductive growth and development of a perennial ryegrass tiller population

Abstract

A population (1188) of vegetative perennial ryegrass tillers was identified at random in nine paddocks of an existing farmlet experiment. Groups of three paddocks (396 of identified tillers) were grazed every 8, 16, and 32 days from mid August until early November 1984, after which all paddocks were grazed every 32 days until the end of the experiment in May 1985. The physiologicalstatus (vegetative or reproductive) oflive marked tillers and their orientation in the sward were determined at 7-12-day intervals during the experiment. Paddock botanical composition and tiller densitywere recorded in October, December, February, and May. Fifty percent of marked tillers became reproductive during the experiment. Reproductive development was concentrated in late October/early November. Different spring grazing frequencies did not affect reproductive development but frequent grazing resulted in tillers that were more prostrate than when grazing was less frequent. Reproductive tillers had a higher overall probability (P = 0.24 per week) of dying than did vegetative tillers (P = 0.09 per week), regardless of grazing treatment. Defoliation during summer/autumnsignificantlyincreasedthe probability of vegetative tiller death. A fast spring rotation increased ryegrass and Poa tiller densities in October after which the effects disappeared.

Effect of altering the grazing interval on growth and utilization of grass herbage and performance of dairy cows under rotational grazing

“…Herbage mass pre‐grazing followed a similar pattern to that of sward height, with treatment AR having lower values than treatment NR in June, and similar values for the remainder of the study. This is in agreement with Thom (1991) who reported that a short spring rotation (minimum 8 d) resulted in lower pre‐grazing herbage masses. Herbage allowance was determined above 4 cm, in accord with previous studies (Meijs and Hoekstra, 1984; Meijs, 1986).…”

“…The impact on the grass plant of combining long and short rotations during the spring and summer has been investigated in New Zealand (Thom, 1991; Thom and Bryant, 1993; Hernandez Garay et al. , 1997), with short rotations shown to have positive effects on tiller density (Thom, 1991; Thom and Bryant, 1993).…”

“…The impact on the grass plant of combining long and short rotations during the spring and summer has been investigated in New Zealand (Thom, 1991; Thom and Bryant, 1993; Hernandez Garay et al. , 1997), with short rotations shown to have positive effects on tiller density (Thom, 1991; Thom and Bryant, 1993). A long rotation length in spring encourages early development of reproductive stems, and subsequent short rotations can utilize this sward efficiently before tillering and the nutritive value of the herbage is reduced because of advanced maturity (Brock and Hay, 1993).…”

“…A long rotation length in spring encourages early development of reproductive stems, and subsequent short rotations can utilize this sward efficiently before tillering and the nutritive value of the herbage is reduced because of advanced maturity (Brock and Hay, 1993). The reported effects of shorter rotations on tiller density, however, have been shown to be transient, with effects disappearing 1 month after short rotations stopped (Thom, 1991). Similarly, the results from the current experiment indicate that any change to the sward from the short rotations dissipated quickly in July.…”

Flowering propensity of two New Zealand perennial ryegrass cultivars originating from different ecotypes

“…In Hamilton, New Zealand (37°47'S), the proportion of reproductive tillers for 'Ellett' was c. 25% in spring (November) of the second year (Table 1). Thom (1991) recorded a slightly lower figure of 18% in a mixed ('Grasslands Nui' and 'Ellett') perennial ryegrass and white clover pasture under dairy cow grazing, at the same research station. However, at a lower latitude (30°24'S) in Natal, South Africa, McKenzie (1997) reported that 'Ellett' tillers were mostly vegetative during spring (<9% reproductive) under subtropical conditions.…”