Effects of nitrogen fertilisation and weed control on nutrition and growth of a four-year-old Araucaria cunninghamii plantation in subtropical Australia

Foliar nutrient concentration and stand growth of a four-year-old hoop pine (Araucaria cunninghamii) plantation, grown on a second-rotation site in subtropical Australia, were examined during a period of 18 months in response to application of nitrogen (N) fertiliser and chemical weed control (WC). Application of either N fertiliser at 50 kg ha-1 or WC of 3-m band spraying along tree rows with glyphosate at 3.6 litres ha-1 (48% active ingredient) resulted in similar, significant improvements in both N nutrition and stand growth in the 18-month period, compared with the control without any N addition or WC. A combination of both N addition and WC further improved the N nutrition and stand growth compared with either the N addition or WC alone. The WC mainly improved the stand N nutrition. Foliar nutrient concentration and stand growth data indicated that N deficiency was a major factor limiting the plantation productivity and there was no significant interaction in improving stand N nutrition and growth between the N addition and WC under the experimental conditions. Additional N fertiliser or WC or both would be required to improve the stand N nutritional status and enhance the plantation productivity 18 months after the initial N and WC treatments.