Abstract
We report on a study of mid-rotation weed control and nutrient management in Eucalyptus pellita plantations in South Sumatra. The study was established at two contrasting sites (representing high and low productivity for the region) that had previously carried three rotations of Acacia mangium. A combination of weed control, nitrogen (N), and phosphorus (P) fertiliser were applied at 1 and 2 years after establishment. We found that the addition of up to 250 kg N ha−1 applied either at 1 year or 2 years after planting did not improve growth. The application of P (30 kg P ha−1) at age 1 year (in addition to 12 kg P ha−1 applied at planting) did not enhance tree growth either. Keeping the plantation free from weed competition throughout rotation (full weed control) enhanced wood volume up to age 4 years at the high-productivity site, while it improved wood volume up to the end of rotation at age 6 years at the low-productivity site. An additional experiment assessing the effect of weed control in the early phase of plantation establishment revealed that weed competition reduced young tree growth of E. pellita substantially. The results of the studies support the current practice of plantation management of E. pellita in the region that applied only P fertiliser at planting time and that kept trees free from weed competition before canopy closure. Full weed control throughout rotation is worth practicing at lower-productivity sites to achieve maximum productivity.
Highlights
We established an experiment with the key research questions to be addressed as follows: (i) does E. pellita respond to additional P and N fertilisers applied at 1 year after planting where leaf area appears to decline? (ii) Is there any benefit from weed control beyond one year of age as the light canopy of E. pellita may promote weed growth? (iii) How long is the critical period of weed interference? Our aim was to understand the value of mid-rotation nutrient and weed management for optimising the productivity of E. pellita plantations in this region
Full weed control throughout rotation improved wood volume at the low-quality site, while weed control up age 1 year was sufficient to achieve high wood volume at the high-quality site
The addition of 30 kg ha−1 of P applied at 1 year after establishment was ineffective in increasing E. pellita growth at two contrasting sites, suggesting that the current P fertiliser application at planting time remains sufficient to support the optimal growth of E. pellita
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Eucalyptus pellita was introduced in Sumatra in early 1990s, but it was not planted on a large scale until the mid-2000s, when it replaced Acacia mangium. A. mangium had been the main species grown for pulp and paper for the previous two decades, but, in the third rotation, a fast-spreading canker-wilt disease caused by Ceratocystis fungi rendered. A. mangium plantations no longer viable [1,2]. E. pellita has been found to be more resistant to Ceratocystis and is a good prospect for wood production, so it has become the species of choice in the region [3,4]
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