Effect of spring grazing management on perennial ryegrass and ryegrass‐white clover pastures

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Abstract
The objective of this study was to investigate the effects of timing and duration of lax spring grazing on tiller dynamics in perennial ryegrass swards, with and without white clover. Two periods of lax grazing—short release (SR) from 26 October to 8 December and long release (LR) from 15 September to 8 December—were compared with a conventional hard grazing—early control (EC). These treatments were applied to swards of perennial ryegrass, with and without white clover, and grazed by sheep. Tiller weight, tiller population density, tiller appearance and death, and stolon population were analysed in a factorial design with three (Experiment 1) and four (Experiment 2) replicates. Tiller weight was increased during the reproductive period, particularly in SR and LR treatments. Also, tiller appearance rate increased in all treatments from September to late January, and was particularly high late in December after grazing of the apices of the main group of reproductive tillers. Lax grazing management increased tiller appearance rate by 53% ( P ≤ 0.05) in Experiment 1 and 23% ( P ≥ 0.05) in Experiment 2, and tiller loss rate by 40% in Experiment 1 (P ≥ 0.05) and 23% in Experiment 2 ( P ≤ 0.05). Over 6 weeks following the return to hard grazing, these effects were reflected in increased tiller population densities of 170, 147, and 115% in LR, SR, and EC treatments respectively in Experiment 1 ( P ≥ 0.05), and 97, 110.5, and 36.5% in LR, SR, and EC treatments respectively in Experiment 2 ( P ≤ 0.05). It is concluded that the increases in herbage production observed in summer‐autumn following imposition of managements which combined lax spring grazing and hard grazing at the time of anthesis, can be attributed to increased tiller densities. The increase was most marked when the period of lax grazing was longer.

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