Effect of topping pastures 1. Pasture accumulation and quality

Three trials examined the accumulation and quality of ryegrass ( Lolium perenne L.)‐ white clover ( Trifolium repens L.) pastures mechanically topped at various stages of flowering during summer. Topping improved herbage quality when the seed head density on pastures was 1200‐ 2000/m 2 but it had no effect when the density was < 600/m 2 . The main effect of topping was to reduce pasture dead matter levels, which improved herbage nitrogen and digestibility. On a pasture containing 2000 seed heads/m 2 , topping reduced the dead matter content (including seed heads) during summer and autumn from 44 to 21–35% and increased the clover content from 6 to 11%. In a second trial where there were 1200 seed heads/m 2 , topping reduced dead matter during summer from 50 to 26–44% and increased clover content from 1 to 2.5%. Pasture quality was improved more by topping ryegrass inflorescences early (between mid emergence and flowering) than late (between the watery ripe and hard dough stages). There were only minimal improvements in pasture quality when pastures were topped more than once, and summer herbage quality was better when pastures during spring were set stocked rather than rotationally grazed. Total herbage accumulation was temporarily reduced after topping, whereas green pasture accumulation and vegetative tiller production were usually similar on topped and non‐topped pastures.