The Effect of Seeding Rate and Perennial Ryegrass Ploidy on Sward Botanical Composition and Herbage Production in Binary Mixtures Under Sheep Grazing

There are numerous benefits to the inclusion of clover and non-leguminous forb species in grassland swards for pasture-based sheep production, however there is a notable lack of management advice available for the use of these diverse swards, representing a significant barrier to on farm uptake. The aim of this study was to investigate the effect of seeding rate (SR) and perennial ryegrass ploidy on sward botanical composition, herbage production and herbage quality of binary sward mixtures under sheep grazing. The swards investigated were perennial ryegrass (Lolium perenne L.) plus white clover (Trifolium repens L.), perennial ryegrass plus red clover (Trifolium pratense L.), perennial ryegrass plus plantain (Plantago lanceolata L.) and perennial ryegrass plus chicory (Cichorium intybus L.). A set total SR of 25 kg ha⁻¹ was used in all treatments, within which clover seed was included at rates of 2.5, 5.0 or 7.5 kg clover ha⁻¹, and forb seed was included at rates of 2.0, 3.5 or 5.0 kg forb ha⁻¹ for the Low SR, Med SR and High SR treatments, respectively. The binary swards were sown with a diploid or tetraploid perennial ryegrass. Results indicate that SR had a significant effect on sward botanical composition and that within the inclusion rates used in this study, SR treatments of 2.5, 3.5, 5.0 and 7.5 kg ha⁻¹, were sufficient for the establishment of white clover, chicory, red clover and plantain, respectively, in a binary sward mixture. The tetraploid swards expressed a lower perennial ryegrass tiller density relative to diploid swards, which was beneficial for the establishment of white clover and plantain.