The impact of herbage mass on perennial ryegrass swards in autumn on autumn and over winter production and characteristics

Accumulating herbage mass to facilitate the extension of the grazing season in autumn is commonly practised. The objective of the current study was to investigate the effect of accumulating varying target herbage masses (THM) in autumn and imposing different defoliation dates (DD), on herbage mass, sward quality and water-soluble carbohydrates in autumn and the subsequent spring. A 4 × 3 factorial split plot design was assigned with four THM (Low ≈ 500 kg·DM·ha⁻¹, Medium ≈ 1500 kg·DM·ha⁻¹, High ≈ 2000 kg·DM·ha⁻¹ and Very high ≈ 3000 kg·DM·ha⁻¹ ) and three DD (DD1—15 October, DD2—7 November and DD3—21 November), across two years. Measurements were carried out at each DD and in spring. Differences in sward quality were found between each THM on different DD. Sward quality reduced from DD2 to DD3 in the high THM (−13 g·kg⁻¹ DM CP, p < 0.001). The very high THM had the lowest sward quality from DD1 (206 g·kg⁻¹ DM CP, p < 0.001 and 787 g·kg⁻¹ DM DMD, p < 0.05). This study has identified the defoliation date of THM in autumn as key to improving autumn management strategies for increased utilisation and sward quality.