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Swietenia macrophylla (mahogany) is native to North America and now it covers a wide range of terrestrial areas in the world including tropical countries. The suitability of mahogany as a plantation crop has led to established 200, 000 ha of plantations worldwide, with extensive areas in Fiji and Philippines (Platino, 1997). In Sri Lanka private sector also started to establish mahogany monocultures especially in the intermediate zone and low country wet zone. However mahogany plantations in the country have not been able to most productive to attract further financial out comes. Nevertheless, information on growth of mahogany is not readily available in Sri Lanka. Since as a solution for this, need to establish appropriate management guidelines for mahogany monoculture plantations. Prior to introduce such management strategies, necessities are identifying growth rates and growth differences of plantation crop of mahogany. Hence this study concerning with distribution of breast height diameter (dbh) of mahogany trees growing in different site types with their age is vital requirement for the plantation sector. Mahogany (Swietenia macrophylla) is an exotic tree, which is heavily adapted to the climatic conditions of wet and intermediate zones of Sri Lanka. Although the state sector manages mahogany with longer rotations, private sector expects to achieve the maximum timber yield within a shorter period. Due to the land scarcity, many of these mahogany plantations have been established in barren and rubber uprooted lands which were heavily degraded. Therefore the soil conditions and site factors directly affect the growth of the mahogany within short rotations.
Seed PropagationI. METHODS OF PROPAGATION Planting materials may be propagated either from seeds or vegetative parts of plants.A. SEEDS OR SEXUAL PROPAGATION
A seedling is a nursery-grown planting material developed from a seed. While most of the nurserygrown seedlings are healthy, some may have defects/ imperfections. These defects may or may not be visible to the eye. Healthy seedlings come from superior seeds. Superior seeds come from selected mother trees. From such source, healthy seedlings ensure higher survival rate and will grow to be vigorous and productive trees. A mother tree has the following characteristics:
Height: the tree is the tallest in the stand of trees Diameter: the diameter of the bole is as big as possible for the species Bole: the bole or trunk of the tree is straight from the base to the top Crown: has well-balanced crown Branches: they are equally distributed and relatively perpendicular to the bole Health: the tree is free from pests, diseases and defects
It is free from injuries such as torn leaves, broken/bent stems, and a nick or a cut on the stem. It is free from diseases such as abnormal development and discoloration of plant parts. It is free from insect infestation such as the presence of ants, grasshoppers, butterfly larvae that usually eat their leaves/stem. It has a relatively thick or woody stem. It has a well-balanced shoot and root ratio. This means that the shoot should be proportionate to the root system to balance the intake and loss of water. For a bareroot seedling, it has a firm and fresh rootsystem with many rootlets.
Ensure healthy seedlings thru proper procedures/ technologies Healthy seedlings can be produced through proper procedures and technologies.
Seed Collection There are three ways to collect fruits/seeds from selected mother trees:
Collection from the ground This practice is common for trees with fruits that fall to the ground after maturity, such as Kamagong (Diospyros philippinensis), Santol (Sandoricum koetjape), Mahogany (Swietenia macrophylla), and Katmon (Dillenia philippinensis). Gather fruits and seeds right after they have fallen to avoid the risk of collecting immature, decayed and/or germinated seeds. Collect fruits that fall during the peak of the fruiting season to ensure higher viability of the seeds. Seeds from fruits collected during the initial, and towards the end, of the fruiting season are usually inferior.
Collection from standing trees Gather fruits/seeds from standing trees by climbing trees either with a safety belt or with the aid of a rope tied on the bare feet. Ladders can also be used to pick the fruits/seeds. Tree climbing is necessary for tall trees with small seeds such as Molave (Vitex parviflora), Bagras (Eucalyptus deglupta), Agoho (Casuarina equisetifolia), or Banaba (Lagerstroemia specbsa).
Collection by shaking branches
Another way of collection is by shaking the branches of the tree either manually or with the aid of a rope tied at the tip of the branches.
Other factors to consider:
Collect seeds from the local source whenever possible and/or in areas with the same climatic condition as the planting site. Collect seeds from fruits or pods that have fallen to the ground before they begin to open and/or germinate. Collect the seeds during the trees regular fruiting season. (Refer to Seed Collection Calendar in Annex A)
Seed Processing Process the seeds properly to avoid damage and attain high percentage germination. Extract the seeds from the collected fruits and immediately dry them for easier storage and transport. Sun or air dry the seeds to save them from fungal and micro-organism infection and insect attack. In addition, separate the seeds from impurities through any of the following methods:
Floatation Submerge the seeds in water. Seeds that float are empty and therefore will not germinate.
Winnowing or Blowing Expose the seeds to the wind. Those seeds that are carried by air will not germinate, thus are useless.
Screening or Sieving Sieve the seeds by shaking or rubbing through a screen until all impurities are removed.
Sorting Sorting separates the defective from the good seeds. This is applicable mostly to bigger-sized seeds.
Seed Testing Seed testing is done to determine the quality and the capability of seeds to germinate into healthy seedlings. This can be done through the following:
Viability test. This is done by germinating randomly sampled seeds using appropriate pregermination treatment to determine how many will germinate. Seed health test. This is done through visual or laboratory examination of the seeds to identify disease-causing organisms, such as fungi, bacteria, viruses, as well as animal pest, such as worms and insects.
Seed Storage and Handling Seed storage is a technique where seeds are kept under favorable environmental conditions to maintain seed viability. This is to keep excess viable seeds for future use when seeds are no longer available for collection. Determine the moisture content (MC) of the seeds if they need further drying or are ready for storage without losing their viability. In general, orthodox seeds (long-lived or with more than a year of viability) require an MC that ranges from 6% to 12%, while recalcitrant seeds (short-lived or with less than one year viability) need an MC that is greater than 12%, depending on the species. (Refer to Annex B for moisture content determination)
Some other requirements in storing and handling seeds:
For seeds stored under room temperature: spread or place them in cloth sacks. For seeds stored in cold storage: keep the temperature at about 10DC for orthodox and about 15C for recalcitrant. For seeds stored in sealed container: dry the seeds to their desired moisture content to avoid deterioration. When transporting, place seeds in sealed containers or securely wrap them in wax paper.
Seed Germination When the seed starts to sprout, germination is taking place. Generally, germination occurs from 3 days to 2 weeks after sowing. However, some seeds germinate longer, depending on species.
Treatment before germination Seeds with hard coats require some treatments for faster and uniform germination. These include any of the following: o breaking of hard seed coats o cold water soak o hot water soak o alternate hot and cold water soak o dry heat treatment o acid and other chemical treatments, such as soaking in sulfuric acid
Methods of sowing a. Sowing in seedboxes Benguet pine (Pinus kesiya), Bagras (Eucalyptus deglupta), Agoho (Casuarina equisetifolia), Kaatoan bangkal (Anthosephalus chinensis), and other species with very small or fine seeds (less than 1 cm in diameter) are sown only in seedboxes. Cover the seeds with fine sand, just enough to ensure surface cover. b. Direct sowing or sowing in seedbeds Large seeds (more than 1 cm in diameter) are either sown in seedbeds or directly in plastic bags and other containers. Examples of these are Ipil (Intsia bijuga), Narra (Pterocarpus indicus), Ma-hogany (Swietenia macrophyiia), Talisay (Terminalia catappa), Teak (Tectona grandis), Lumbang (Aleuhtes moluccana), among other species. Simply press the seeds into the soil until they are half covered. The preferred sowing materials or germination soil mix consist of 50% sieved washed river sand and 50% top garden soil. Water the sown seeds using a sprinkler with fine holes close to the soil to avoid dislodging of seeds. Continue watering every day - early in the morning or late in the afternoon until the seedlings are ready for potting. For very fine seeds, water them very carefully so that the seeds are not eroded.
Preparation of potting materials
Sterilize the soil before using it as potting material to avoid problems with soil-borne diseases, such as damping-off and root rot. This is done using any of the following methods:o o o o
heat the soil over a fire for about 15 minutes apply chemical disinfectant (fungicide) pour boiling water spread the soil under direct sunlight in a clean area for one or two days.
Transplanting a. S