Summer pasture yield variation in a central Waikato location from 1979 to 2010: implications for pasture persistence.

Three datasets spanning 31 years (1979-2010) of net herbage accumulation (HA) for Waikato dairy pastures were studied to determine between-year variability in summer HA. In addition, a dairy farm at the same location was modelled with the DairyNZ Whole Farm Model, using climate data for 15 years to predict HA, and milksolids production. Measured extremes for HA over 5 months (1st December to 30th April inclusive) were from 4.7 to 9.1 t DM/ha, with a mean of 7.0 t DM/ ha ±1.2 t DM/ha SD. Rainfall during these months had a positive impact on HA, with an extra 849 kg DM/ ha (r2=0.43, p