Tree information

Local name: 

Khayer

Genus: 

Acacia

Species: 

catechu

Author: 

(L.) Willd.

Family: 

Leguminosae

Middle-sized tree; twigs with paired recurved thorns; flower pale yellow in cylindrical spikes; pod flattened, brown, shining, 5-7 cm long, containing 6-8 seeds. A useful multipurpose tree for the Terai and lower hills, fairly easy to establish. and of considerable commercial importance as the source of katha and cutch.

Characteristics

It is a strong light-demander. It grows naturally on a wide range of soils, preferring well-drained, coarse, gravelly alluvial soils, but it also tolerates heavy clay and calcareous soils. On old river terraces near Pokhara it grows well on soils with pH values between 7.4 and 8.9. It is used in India for reafforestation of eroded slopes. It will withstand flooding. The seedlings are somewhat susceptible to severe frosts, but from the sapling stage frost damage is slight. However over most of its range, and the areas where it is likely to be planted, frost is not a major problem. It is very drought-resistant It needs to be protected against grazing and browsing. Acacia catechu is deciduous, shedding its leaves about February, and putting out new leaves at the time of flowering, in June. It coppices well, unless it is in mixture with other species, when these tend to shade out the coppice shoots. The seedling, like that of most acacias, develops a strong taproot.

Occurrence

In Nepal it is widespread in the Terai, and extends to about 900 m (exceptionally to 1400 m). It is very characteristic of the edges of broad river channels in the Terai and dun areas, and often extends some way into the beds of river. It also grows freely on the high gravelly terraces of the Seti River near Pokhara at a considerable elevation above the water level. It is not, however, confined to such sites, and is fairly tolerant of soil conditions. Outside Nepal it occurs throughout most of India and extends to Thailand and southern China.

Natural regeneration

The pods ripen, turning from green through reddish-green to brown, from the end of November to early January. They dehisc soon after ripening, and began to fall in January though some may remain on the tree until October; by this time, however, most of the seed has been destroyed by insects. The seeds remain attached to the pod valves. which may be blown considerable distances by winds; seed is also disseminated by water. Regeneration is most profuse on exposed alluvial soil in or near river beds. In the open the seedlings wiIl usually be able to develop freely, but under shade most of them will die due to damping-off and other causes. As stands become older and elevated above the river bed, due to changes in the course of the river, the ground becomes harder and drier and natural regeneration ceases. Apart from unfavourable soil conditions, the main factor limiting natural regeneration is excessive grazing.

Artificial regeneration

The seeds are sown directly into 3 inch x 7 inch (7.5 cm x 18 cm) polypots at the rate of two seeds per pot. A mulch of grass or similar substance is used to cover the soil in the pot immediately after the seed is sown; as soon as most of the seeds have geminated it is removed. If it is thought that germination rates may be poor, the seed can be pre-germinated. Scarified seed is sown very densely on a well-prepared seed bed or tray, pressed down with a flat piece of wood, covered lightly with sand, pressed down again, and covered with a mulch. As the seeds germinate and produce roots 5-10 mm long, they are removed daily and re-sown into polypots with the rootlet downwards, at such a depth that the seed coat is just covered in soil.

In the Terai the seed should be sown in the first two weeks of April, elsewhere in the last two weeks in March, to produce plantable seedlings 20-30 cm tall by mid-July. In the Terai 12-14 weeks in the nursery is needed, and elsewhere 14-16 weeks. If planting earlier than mid-July is envisaged the sowing dates should be adjusted accordingly. If, shortly after germination is complete, there are two seedlings in a pot one of these should be removed and either pricked out into empty pots or thrown away. Four to five weeks after sowing the pots should be spaced so that there is a 5-10 cm gap between the rows of pots, and at the same time roots should be pruned. This root pruning must be continued every 10-14 days, as acacias develop very vigorous taproots. If root pruning is delayed wilting and dying back of the seedlings is likely to occur. Seedlings which have been kept too long in the nursery should be thrown away, as the strong taproot development will prevent successful planting. No shade is needed, except for two or three days just after seedlings have been pricked out. Stump plants have been used in India, but generally give poorer results than seedlings raised in pots; this method is not recommended. Bare-root plants have given very poor results.

Acacias have a symbiosis with Rhizobium bacteria, which fonn nodules on the roots and fix nitrogen; however artificial inoculation with Rhizobium is usually unnecessary, but mixing a little topsoil from A. catechu stands into the potting mixture is a useful precaution, if such soil is available near to the nursery.

The chief danger to plantations of A. catechu is browsing by domestic animals, and if this is likely to be serious effective fencing will be needed.

Planting should not be later than mid-July. For most purposes a planting dlstance of 2 m x 2 m is suitable. Even in plantations intended to be grown on very short rotations for the production of small fuelwood, closer planting is undeslrable, as competition results in plants with very much reduced diameters. At Adabhar in a plantation, 18-month-old trees planted at 1 m x 1m averaged 1.7 cm in diameter, while those planted at 2 m x 2 m averaged 5.8 cm. The basal area per hectare of the widely spaced trees was nearly three times as much as that of the closely spaced ones. Regular weeding is necessary for at least two years after planting.

Good results have also been obtained by direct sowing of Ireated seed. Near Pokhara seed was sown in normal planting pits, with the soil filled back in, at the rate of 3-4 seeds per pit. Germination was good and the resulting seedlings vigorous and healthy. If seed is sown in pits, the seedlings should be thinned out to one per pit during the second season after planting. In India the seed is sown in hoed strips 60-90 cm wide and about 4 m apart, often in conjunction with agricultural crops. The crops should not be sown within the hoed strips. Seedlings should be thinned out to one vigorous seedling every metre in the second year. with a further thinning after another 2-3 years, to leave the trees about 2 m apart within the lines.

At lower altitudes if plantations are well tended early growth is rapid. At Adabhar 18-month-old trees averaged 4.7 m in height by 5.8 cm in diameter; at Butwal 34-month-old trees were 5.8 m high with a diameter of 6.5 cm. A trial plot 5.5 years old at Tarahara, Sunsari District, at about 200 m altitude in eastern Nepal gave a green weight yield of stem and branchwood of 79 t ha-1 , or a mean annual increment of 14.4 t ha-1 . This was the highest yield on this site, slightly more than that of Acacia auriculiformis and over 40 per cent more than the yield of Dalbergia sissoo or Eucalyptus camaldulensis. In Uttar Pradesh a crop height of 11.3 m by 12 cm diameter is reached in 10 years, and 16.2 m by 19 cm in 20 years (Indian Timbers, 1973). For cutch production fairly long rotations are needed, as the proportion of heartwood increases with age. Diameter growth in congested natural stands can be very low; for this reason regular thinnings are essential, particularly in plantations originating from direct sowing. S.P. Singh and Jain (1987) recommend that for the maximum production of cutch there should be 560 trees ha-1 at 10 years; this will produce good yields of cutch on a rotation of 30, 50, or 60 years on good, medium and poor sites respectively. For volume tables see E.R. Sharma and Pukkala (1990b).

The seed ripens from November to March, according to the locality; January and February are the most usual months for collection. The ripe pods are a dark chestnut-brown and collection should take place as soon as they begin to open on the trees and release the seed. Seed collected in April has given poor germination. It is extracted from the pods by drying them and beating them with sticks. Each pod contains 3-6 seeds. There are 30,000-40,000 seeds kg-1; an individual tree will yield 0.5-2 kg.

The seed should be dried thoroughly and stored in well-sealed polythene bags. As it is very liable to borer attack, a little contact insecticide should be mixed with the seed in the containm. Treated in this way the seed should remain viable for a number of years. Reported short viability, of the order of 6-8 months, may be due to poor storage conditions. As seed is produced in abundance every year long periods of storage should rarely be necessary. The seed needs pre-treatment before it is sown. Small quantities of seed can be scarified by cutting off a small portion at the end opposite to the hilum. For larger quantities hot water treatment is easier; the seeds are immersed for 2-3 minutes in 15 times their own volume of water which has been boiled and then removed from the heat; they should then be soaked in cold water for 24 hours. Germination of scarified seed begins 3-4 days after sowing, and is complete 6-7 days later. Seed treated with hot water takes 1-3 weeks to germinate. Germination varies from 30 to 80 per cent. Under field conditions in Nepal usually between 5,000 and 10,000, occasionally 20,000 plants, have been raised kg-1 of seed.

Importance in Nepal

There are several quite large factories producing katha, mainly for export to India. A typical factory will produce about 400 t yr-1, from about 7000 m3 of timber. Natural forest in India, with scattered A. catechu, is estimated to have an annual increment of only 0.06 m3 ha-1 (O.P.Sharma, 1984); thus the production of a smgle factory would require over 100,000 ha of natural forest if it were to be maintained. The same yield could be produced by 1200 ha of plantation, at a guess, assuming a low mean annual increment of 6 m ha-1. Thus there is a strong case for establishing plantations for the katha and cutch industry, and proprietors of factories should be encouraged to do this. Apart from this, A. catechu is a useful multipurpose tree, producing fuelwood, small timber for village use, and fodder. It grows well on gravelly bouldery soils which are not good for agriculture, and couId be a useful tree for community plantations in lowland Nepal. However, though in the Chitawan area local people plant it near their houses for timber, it is otherwise not in great demand for planting, as most people in the Terai prefer to plant Dalbergia sissoo.

The most important commercial products from A. catechu are katha and cutch, obtained by boiling chips of the heartwood. Katha, an impure form of catechin, is mainly used for chewing with betel nut and pan, and also has medicinal and pharmacological uses. Cutch, catechu tannic acid, is used in tanning and dyeing ships' sails. At one time it was widely used to preserve fishing nets and lines, but the increase in the use of nylon fishing nets is reducing the demand for this purpose. It is also used in oil-drilling operations. Acacia catechu heartwood contains 4--6 per cent of catechin and 10-12 per cent cutch (O.P. Sharma, 1984). The wood is hard and heavy, with a specific gravity of about 0.7 air dry, and a calorific value of about 25,600 kJ kg-1. It is excellent for fuelwood and charcoal (Chaturvedi et al., 1986). It is also used for poles in house construction, and for rice pestles, oil crushers, and ploughs. The sapwood is not durable, but the heartwood is very durable. However its value as a source of katha precludes its large-scale use as timber. In India it is reputed to be a good fodder and is lopped to feed goats and sometimes cattle; however it seems to be less popular in Nepal. The leaves contain 12-18 per cent crude protein, and 46 per cent total digestible nutrients.

Allometry

Stem Biomass: 

[Ln W (kg)] = -4.300 + 0.434 * [Ln DBH (cm)]

Branch Biomass: 

[Ln W (kg)] = -5.902 + 3.56 * [Ln DBH (cm)]

Related

 

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