Comparing within paddock yield variability of perennial ryegrass monocultures and perennial ryegrass, white clover and plantain mixtures using yield mapping

Diverse mixtures of pasture species have greater potential for exploiting niches within a paddock compared to monocultures resulting in less variability in pasture growth within the paddock. It is unknown if the variability occurs at a scale that is relevant in intensively managed dairy systems. This study assessed the variability in pasture biomass within 6 split paddocks sown to either perennial ryegrass monocultures (PRG) or perennial ryegrass, white clover and plantain mixtures (RCPM) on a dairy farm in north-west Tasmania. The biomass present in each area was mapped immediately prior to grazing in the spring of 2014 and autumn 2015 using a C-Dax pasture meter with a GPS console. Data was interpreted through the Manifold GIS software before being analysed in the R statistical package. There were no significant difference in pasture biomass between the PRG and RCPM treatments, with mean pasture biomass of 2997 and 3162 kg DM/ha respectively. The variation in pasture biomass within each area (as assessed by the co-efficient of variation) was greater in the PRG areas (16.6%) than in the RCPM areas (13.4%). The overall difference between the within plot standard deviation and coefficient of variation for the treatments was small at 65 kg DM/ha and 3.2% respectively. Diverse pastures have increased opportunities to exploit niches existing within dairy paddocks relating to soil diversity. This and other studies suggest that exploitation of niches only has a small impact upon within paddock yield variability.