Pasture formulation for optimised yield and weed suppression under sheep grazing and irrigation in Canterbury

Farmers need evidence to make decisions about what forage species and how much of each species to use in their pastures. This paper provides data from a study that aimed to formulate a sheep pasture from a diverse pool of six species. At Lincoln University, 69 monocultures and mixtures varying widely in sown number and proportions of perennial ryegrass, cocksfoot, plantain, white clover, red clover and subterranean clover were examined under sheep grazing for 4 years. Measured pasture functions were annual total herbage and weed yields. On average total yield increased and weed yield decreased with increases in number of species, but species’ proportions determined the optimal pasture. For example, on average six-species mixtures had 1.6 t/ha more total yield and 1.8 t/ha less weed yield than two-species mixtures (12.1 and 3.1 t/ha) at year 1. However, several pastures of equal number of species had above-average total and below-average weed yields. The pasture that maximised yield and weed suppression (14.1 and 0.3 t/ha per annum) had sown proportions of 0.5 ryegrass and 0.25 each of white and red clovers based on seed count; equivalent to 9.7, 1.3 and 9.0 kg/ha for a total sowing rate of 20 kg/ha.