Sustainability of New Zealand high‐country pastures under contrasting development inputs. 3. Sheep carrying capacity

Abstract

Annual sheep‐grazing‐days over 14 years is reported for two grazed, mixed‐species pasture trials on a Pukaki/Tekapo high‐country soil. One compared 30 combinations of 5 superphosphate rates (0–500 kg ha^‐1 yr^‐1) × 3 stocking rates × 2 stocking methods; the other compared 27 combinations of P and S fertiliser (0–100 kg element ha^‐1 yr^‐1). Carrying capacity increased with both S and P fertiliser from 2.3 grazing‐days/365 ha^‐1 yr^‐1with zero fertiliser, to 20.9 under high fertiliser and irrigation. Carrying capacity was 11–27% less under sustained or set‐stocking than under mob stocking, the difference increasing with mean carrying capacity. There were several time trends in carrying capacity: a year to year fluctuation related to positive effects of Sep‐Dec rainfall and negative effect with March temperature; the difference between treatments increasing in good years; an increase or decrease to asymptote carrying capacity dependent on P fertiliser rate; and an increasing positive effect of S fertiliser.

Keywords:

• New Zealand
• high country
• fertiliser
• sustainability
• carrying capacity