Effect of Organic Amendments on the Growth of Gaharu (Aquilaria malaccensis)

Abstract

Aqularia malaccensis or commonly known as 'Gaharu' is famous for its heartwood that is fragrant and highly valuable. Since 2018, the International Union for Conservation of Nature (IUCN) has reported a decline in the A. malaccensis population caused by agricultural and heartwood activities. Reforestation and transplanting of the A. malaccensis is essential to preserve the genetic diversity at the species level. Previous studies on the production growth of A. malaccensis have been focussing on using different types and fertilizer regimes to enhance its growth for conservation and restoration effort. However, knowledge on the potential of enhancing the growth of A. malaccensis using soil amendments derived from organic sources is limited. Therefore, this study aims to compare the effect of organic soil amendments derived from four different sources on the growth of A. malaccensis. Saplings of A. malaccensis were employed in a glasshouse experiment following a complete randomized block design with 5 treatments × 4 replicates to ensure validity and minimise variability within treatments. The five treatments were saplings grown with no addition of organic amendments serving as control (C), forest litter (FL), chicken manure (CM), insect frass (IF) and empty fruit bunch mixed with Azolla sp. (EFBA). The saplings grown in polybags were placed randomly on a 9 x 9 grid within the nursery, 0.2 m apart and watered daily using an automatic sprinkler system. Physical characteristics of the saplings and other environmental parameters were measured. The saplings of A. malaccensis increased in mean height when grown in soil amended with CM, IF and EFBA. In contrast, there were no significant effect of organic amendments of plant stem diameter, number of shoots and leaves. In addition, the stem diameter for saplings grown in soil with organic amendments were weakly and negatively correlated to soil temperature. This study indicated that that the organic soil amendments derived from different sources had a significant role in the plant's resource allocation during the saplings stage. Further studies on the plant, organic amendments and soil physicochemical traits are needed to explain the interaction between these components for the better conservation effort.