Effect of herbicides on woody weed control and growth of plantation eucalypt seedlings

Abstract

Summary Various herbicides were applied to control woody weeds on a granitic soil, before and after planting with open-root and paper-pot seedlings of Eucalyptus regnans F. Muell. and Eucalyptus nitens (Deane et Maiden) Maiden. All herbicide treatments resulted in significantly reduced weed cover during the first six months after planting. For six treatments, weed control effects persisted for at least two years. The growth response of eucalypt seedlings was related to both weed control effects and direct herbicide effects. Post-plant applications of atrazine reduced the survival of paper-pot seedlings. High residual levels of atrazine were associated with growth losses. Lower residual levels of atrazine gave significantly better growth and a direct growth stimulation was indicated. For the study site, atrazine at 4 kg active ingredient ha−1 was an effective and safe herbicide for pre-plant application to plantation seedlings of E.regnans and E.nitens.