Optimum spot weed control treatment for a New Zealand radiata pine (Pinus radiata) plantation

A trial was established in the South Island of New Zealand to investigate the response of Pinus radiata to varying the area and duration of weed control around individual trees. Results after six years demonstrated that weed control was essential to ensure maximum survival and growth of Pinus radiata seedlings. Maintaining weed control for two seasons following planting resulted in marginally higher stand productivity than where weed control was applied in the year of planting only. A modelling approach was used to determine treatment effects in terms of a "time difference", and to make inferences on long-term treatment effects. Without weed control, tree volume six years after planting was more than 1.5 years behind trees given complete weed control. Spot vegetation control resulted in similar tree growth to total control, as long as the area and duration of weed control was greater than a I m spot maintained for I year.