Eucalyptus

Site factors

Eucalyptus camaldulensis is a common and widespread tree species. It is a best suitable tree species for the areas which received rainfall from 250 to 600 mm at the same time it can also grow well in high rainfall areas which receives as high as 1250 mm. The success of Eucalyptus is attributed to its superiority to other trees in production of wood on infertile dry sites, its tolerance of extreme drought and high temperature. This species occurs on a variety of soil types from red or black soils to sandy alluvial soils. It can also grow well in salt affected areas.

Planting stock

Institute of Forest Genetics and Tree Breeding (IFGTB), Coimbatore has released four Eucalyptus clonal varieties viz., IFGTB­EC1, IFGTB-EC2, IFGTB-EC3 and IFGTB-EC4 for cultivation in Tamil Nadu and Andhra Pradesh. These clones are multiplied and supplied based on prior request. About 20% improvement in yield is expected from these clonal varieties. IFGTB  sells seeds to the farmers at the cost of Rs. 10000/- per kilo gram.

Seed collection, processing and Nursery techniques

Seed are mixed with chaff and can be difficult to distinguish from chaff. Seeds weigh approximately 700 seeds/gram (Ralph, 2003). About 100 - 500 germinant can come per gram of seed. The seeds with about 5% moisture content can be stored for more than 10 years if they are placed in hermetic containers at a temperature of 3 to 5 °C.

The texture of the medium of germination must be fine. A fertile mixture of soils with sand in a proportion of 1:1 must be used. Seed should be sown under shade on a free-draining and sterilized medium and covered very sparingly with inert material (e.g. sand). Seeds must be sowed deep enough to prevent uncovering when watered, but they must not be too embedded. The germination period for this method ranges from 4 to 5 days. The seedlings are lifted from the mother bed when they are 5 to 7 cm in height and transplanted in poly bags. Alternatively, seeds can also be planted directly into bags using special devices, such as syringes, to place two to four seeds in each bag.

Partial shade is needed after transplanting till six weeks. Plants reach plantable size of 30 cm in four to five months. Seedlings require periodic watering in the first stages of development. Common mistakes in propagation are over-watering and associated disease problems, over-shading and allowing the germinants to become too large for easy transplanting leading to malformed tap roots or root curling in the pots. To prevent damping off, cupric fungicides should be applied. About 1-2 lakhs seedlings can be obtained from 1 kg of seed in nurseries.

Plantation management

Weeding and burning of underbrush are recommended before planting. The ability of the species to compete with weeds is poor. In high rainfall areas, extensive weeding (2-3 times) must be applied until crowns close (2-3 years). Inadequate weed control may lead to complete failure of the planting.

A spacing of 3 m x 2 m (1667 stems/ha) is often applied for pulpwood. Wider spacing of 4 m and 2 m (1250 stems/ha) or 5 m x 2 m (1000 stems/ ha) are recommended when larger trees are required. For energy plantations, a spacing of 2x2 m is recommended.

Application of 100g of NP or NPK (3:2:1) fertilizer to each tree at planting to assist establishment of growth is common. Crown die-back during dry-season as a result of boron deficiency is prevalent in few places. A dosage of 10-20 g of borax per tree depending on soil type is applied.

In India, Eucalyptus is managed through clear-felling system followed by coppice rotation to a maximum of three times. After three rotations, the below ground biomass is taken out and replanted with seedlings.For pulpwood depending on the fertility and availability of water, the rotation can fixed from 5 year to 7 years.

Agroforestry practices

At a spacing of 3 x 2 m intercropping can be carried out for one year. In irrigated sites, shade loving crops can be cultivated during second year also. A wide range of crops can be grown when the spacing is 5 m x 2 m which supports intercropping up to three years.

Yield

In Tamil Nadu, about 25-30 t/ha at a rotation of 6-7 years was realized through seed raised plantations during early 1990’s. Introduction of clones increased the yield up to 60-70 t/ha in six years rotation. Through site-clone matching, a yield of 100-150 t/ha was achieved in five years rotation depending on the fertility level of the soil.

Important insect pest and diseases

In the nursery, it is susceptible to diverse fungi causing damping-off, collar rot and leaf diseases. Attention to nursery hygiene and care not to over-water are preferable to chemical controls.

Eucalyptus in irrigated farm lands                                             Eucalyptus in drylands

Eucalyptus intercropped with Blackgram

Termites affect planted seedlings young trees and must be chemically controlled. Eucalyptus is severely attacked by an invasive gall insect (Leptocybe invasa) which lead to formation gall like structure in the midrip and petiole and young stem. The problem is severe in young seedlings and coppice shoots. Chemical treatments do not found to be suitable.

Uses

Wood is used mainly for poles, posts, fire wood, charcoal and paper pulp. It is also used for hardboard and particle board.

Source: Transfer of Tree Cultivation Technologies to Krishi Vigyan Kendras - Publication by Institute of Forest Genetics and Tree Breeding, Coimbatore.