Bambusa arundinacea - Thorny Bamboo

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Bamboos are woody perennial grasses that occur in the tropical and subtropical evergreen and deciduous forest formations of Asia-Pacific. Important uses of bamboo include paper and pulp industry, fuel, food, feed, house construction, and scaffolding, making several articles of everyday use, besides controlling soil erosion. One hundred and thirty wild and cultivated bamboo species are reported to occur in India. They exist under diverse ecological conditions, often as an under-storey in many forest types. In agroforestry, thorny bamboo is perhaps the most important species in Kerala.

 

Propagation


Bamboos are propagated either by seeds or vegetative means (offsets, division, culm/ rhizome cuttings or layering). In general, bamboos are monocarpic, i.e. they flower only once and die after producing seeds. Most of the economically important bamboos flower gregariously at long intervals of 30-40 years. Although large quantities of seeds are produced during gregarious flowering, they are viable only for about six to eight months. Seeds can be germinated in nursery beds and pricked out into polybags of size 18 cm (flat width) x 22 cm. One year-old seedling can be used for planting. However, when seeds are not available, bamboos are propagated vegetatively. 

Propagation by offsets is the common method of vegetative propagation. One-year-old culms in a clump are given a slanting cut at about 90 to 120 cm above the ground. The rhizomes to which they are attached are dug out with the roots intact. The shoot portion is then cut off to a length sufficient to include a well-developed bud. These offsets are planted out sufficiently deep in the soil to cover the first two or three nodes. Planting should be carried out immediately before the rainy season. During extraction care must be taken to avoid damage to roots and rhizomes of mother clumps.


Work at the KFRI has shown that using rooted culm cuttings is a viable alternative to the laborious offset method. For vegetative propagation using culm cuttings, extract 2 to 3 year old culms from healthy clumps by cuttings just above the first node during March-April. Trim the leaves and side branches without injuring the axillary buds. Prepare two-node cuttings (leaving about 57 cm on either side of the nodes) using a sharp knife or saw. Make a small slit (about 2 m long and 1 cm wide) or drill holes (about 7 mm diameter) in the middle of the inter node. Wrapping in moist gunny bag or embedding in boxes containing moist saw dust might minimize exposure of the cuttings. Pour about 200 ml of NAA (1naphthalene acetic acid) solution (100 ppm) carefully into the culm cavity through the slit and close the slit/hole by wrapping with a polythene strip. Ensure that the polythene wrapping is tight so that the solution does not leak out. After extraction, the culm cuttings should be treated with NAA as quickly as possible. 

Prepare raised nursery beds of 10 m x 1 m and fill with a mixture of soil and sand (3:1). One week prior to planting, drench the nursery bed with 30 litres of carbendazim 0.05 per cent to prevent fungal attack. Place the cutting horizontally (the opening facing upwards) across the nursery bed. About 5060 cuttings may be conveniently planted in a raised nursery bed. Cover the cuttings with a thin layer of soil. Provide shade and water the beds regularly till the onset of monsoon but avoid waterlogging. Rooted cuttings can be transplanted to the field in about four months.Cuttings sprouted and rooted at both the nodes of a culm cutting must be separated carefully through the middle to get two plants.


Propagation by division is usually done in the case of dwarf bamboos, which are easy to handle. It involves splitting / dividing the mass of rhizomes and planting out the culms in small clumps with two or three culms attached. Other methods of vegetative propagation include rhizome cuttings and air layers. Sections of fresh living rhizome of the preceding year about 15 to 30 cm long containing at least one bud and air layers form successful means of propagating some bamboo species.

 

Planting and fertilization

Spacing recommended for mono-specific bamboo plantations is 10 m x 10 m. Propagules can be planted in pits of size 45 cm x 45 cm x 45 cm. Fertilizers may be applied @ 40 g N,

10 g P2O5 and 75 g K2O per plant per year in 1-2 year old plantations.

Competitive interactions in bamboo-based agroforestry


Being perennial grasses, bamboos have higher root length densities than dicots. Thus in mixed species system, bamboos may out-compete the field crops or other tree crops grown in association. However, interspecific competition in bamboo-based agroforestry systems can be overcome by planting crop 8-9 m away from the bamboo clumps. Trenching (30-40 cm wide and 50-60 cm deep at 5-6 m away from the clumps) to spatially isolate bamboo roots from the rest of the crops is recommended, if crops are to be planted at shorter distances. Bamboo root competitiveness is usually a function of its rooting intensity with crown radius. Larger clumps have wider foraging zones usually extending to about 8 to 9 m. Therefore canopy reduction treatments such as pruning and culm thinning are appropriate to surmount interspecific competition. Pruning up to a height of 1.5 above the ground is recom-mended in plantations of four year and above. Also remove the dry and dead culms from the centre of the clump to reduce congestion.

 

Pests and diseases

The bamboo plantations in Kerala do not face any serious insect problems. Young plants, however, are likely to be affected by shoot borers and sap suckers. In bamboo nurseries, damping off caused by Rhizoctonia solani is a major disease. It can be controlled by prophylactic fungicidal treatment and by regulation of shade and watering. In young plantations, rhizome bud rot (Pythium sp., Fusarium sp.), rhizome decay (Pseudomonas sp.) and basal culm decay (Fusarium sp.) are important.

 

Extraction of bamboo culms
Either all the old culms, i.e. those more than three years old (six years in the case of clumps regenerated from seedling) or a certain number of mature culms are removed annually. Older culms in the interior of the clumps should be removed in a horseshoe pattern. The height of cuttings is usually at 30-50 cm above ground. It is necessary that cuttings should leave at least one node above the ground to prevent rainwater soaking into the rhizome.

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