EFFECTIVENESS OF ORGANIC POTTING MEDIA FOR RAISING MAHOGANY (<em>SWIETENIA</em> <em>MACROPHYLLA</em>) SEEDLINGS IN WESTERN SAMOA

Abstract

The suitability of two organic potting media for raising mahogany (Swietenia macrophylla King) seedlings was compared with the standard operational practice of using forest soil. Several rates of addition of a slow release nursery fertiliser were added to each growth medium. Effects of treatments on nursery growth and subsequent performance in the field were assessed. Seedling heights at the end of the nursery phase (111 days) were greatest in pots with soil without added fertiliser, and in brewers waste/ sawdust and coir potting media with a moderate amount of slow release fertiliser (4g 1^-1). Both increasing and decreasing the rate of slow release fertiliser from 4g 1^-1 reduced seedling height. Ten months after planting out in the field, the trees raised in coir in the nursery were significantly greater in height, diameter and volume than trees raised in a soil medium. These results suggest that the use of organic nursery media can produce seedlings that grow significantly faster in the first year after outplanting than seedlings raised in soil. Further research is required to refine the characteristics and method of preparation of the organic media, using raw materials which are freely available in Western Samoa.