Rotation Length and Defoliation Intensity Effects on Dry Matter Production and Botanical Composition in Perennial ryegrass–White clover and Multispecies Pastures

Temperate grazing systems require advanced management strategies to simultaneously enhance both productivity and resilience. Multispecies pasture (MSS) mixtures offer a promising alternative to conventional Lolium perenne-Trifolium repens (LP-TR) systems by leveraging niche complementarity through diverse and deeper rooting profiles that enhance drought tolerance and optimize nutrient acquisition from heterogeneous soil layers. In a field study, we compared LP-TR pastures with three functionally distinct MSS pastures subjected to varying rotation lengths (RL) and defoliation intensities (DIs). Seasonal and annual dry matter (DM) yield and botanical composition were assessed. MSS consistently outperformed LP-TR in total DM production, especially under shorter RL, which had a more pronounced effect on annual and spring biomass than DI. An 8 cm defoliation height generally enhances DM accumulation across systems. Species interactions significantly influenced botanical composition, with Plantago lanceolata contributing to greater pasture stability under environmental stress, accounting for 24–61% of total herbage DM. Furthermore, RL and DI interactions affected species prevalence, underscoring the need for adaptive, species-specific management strategies. These findings demonstrate that integrating strategic species selection with tailored defoliation practices in MSS mixtures can substantially enhance pasture productivity, compositional stability, and long-term sustainability of temperate grazing systems.