Graze less, grow more? Leaf stage defoliation management of diverse and ryegrass-based pastures in Golden Bay, New Zealand

Abstract

With climate change, and rising fertiliser costs, lowcost pasture growth strategies are needed for New Zealand farmers. This study compared functionally diverse pastures, (six grasses, four legumes, two herbs) with standard perennial ryegrass-white clover under high-rainfall, moderate fertility conditions in Golden Bay. Over three years, a 2×2 factorial study applied two defoliation intervals across two pasture types: cut when the standard pasture reached the 2.5-leaf stage (2.5LS) and when the diverse pastures reached the 3.0-leaf stage (3.0LS). In 2024, diverse pastures matched standard
pasture in dry matter produced. Yield differences between treatments occurred seasonally in 2024, with standard pasture cut at the 2.5LS growing 12% more biomass than diverse pastures during autumn. In spring, both pasture types cut at the 3LS produced 20% more than pastures cut at 2.5LS. In summer 2024–25, defoliating at 3LS defoliation grew 9% more than
the 2.5LS. Sown species declined from 85% (year 1) of total dry matter to 50% by year three. Seasonal rainfall was average, though late autumn sowing may have impacted subsequent persistence. These findings show that defoliation interval has a greater impact on increasing seasonal yield than the pasture mixtures compared. However, well-managed diverse pastures can match or in some seasons exceed ryegrass-white clover systems.