RUBBER

Nursery Management

Rubber seeds lose viability very rapidly if left in the field. The seeds are therefore picked up daily during the seed fall season and quickly transported to nurseries for germination and planting. Planting materials for establishing rubber plantations are generated in ground and polybag nurseries.

Ground nursery

Ground nurseries are established for the production of budded stumps, stumped buddings and budwood.

Selection of site

1. The site should have good accessibility for supervision and transport of materials.
2. A good soil depth of at least 75 cm is essential
3. Loamy soils are ideal
4. A well-drained level area is ideal. Undulating lands are also suitable if adequate soil conservation measures are adopted
5. Contour terracing is done where the slope is in excess of two per cent
6. Waterlogged areas should be avoided and water table should be sufficiently low to allow sufficient soil depth for root development
7. Shade-free areas are preferred
8. Land with a history of intensive cropping needs proper build up of the nutrient status to the satisfactory level

Preparation of nursery beds

1. Dig to a depth of 60-75 cm. Stones, stumps, roots, etc. present in the soil are removed and the soil is brought to a fine tilth
2. Beds should be 90 to 120 cm wide and of convenient length. In the level lands, raised beds are made with footpaths of about 45 cm width between the beds. In undulating lands, beds are prepared along the contours, one below the other
3. At the time of preparation of nursery beds, 25 kg of compost or well-rotten cattle manure and 3.5 kg of powdered rock phosphate (20% P2O5) are incorporated for every 100 m2 of nursery bed.
4. When nurseries are established in newly cleared forest areas rich in organic matter, compost or cattle manure need not be applied during the first year. Similarly when the same area is repeatedly used as a nursery, rock phosphate need be applied only once in three years. Drainage and pathways should be provided appropriately.

Seed germination beds

1. A well-drained area with moderate shade is the ideal site for germination beds
2. Level beds of 90 cm width and convenient length are prepared with walking space in between. The beds should be raised 10-15 cm above the soil surface to avoid water-logging
3. A free-draining friable material like river sand, spread above the bed to a thickness of 5 cm, is used as the medium for germination. Seeds are washed thoroughly to remove charcoal and other packing debris and spread over the bed in a single layer touching one another and pressed gently into the sand
4. In order to prevent loss of too much moisture from the rooting medium, the beds are covered with a thin layer of gunny bag, coir matting or similar material. A high level of moisture is maintained in the bed by evenly sprinkling water early in the mornings and late in the evenings
5. Germination of the seeds starts within 6-7 days after sowing. The beds should be inspected daily and the germinated seeds picked up and collected in a bucket containing water as soon as the radicle emerges for planting in the nursery beds or main field. Seeds, which do not germinate within two to three weeks, should be discarded

Planting in nursery

1. Small holes enough to accommodate the seeds in a horizontal position and approximately 5 cm deep are made
2. The seeds are carefully placed in the holes with the radicle pointing downwards and covered with soil
3. The sprouted seeds should be planted when the young root is less than 2 cm long
4. The common spacing adopted are:
   • Seedling stumps: 30 x 30 cm
   • Green-budded stumps: 23 x 23 cm
   • brown-budded stumps: 30 x 30 cm or staggered pairs of rows 60 cm apart and 23 cm between plants
   • Stumped buddings: 60 x 60 cm, 90 x 30 cm, 90 x 60 cm or 90 x 90 cm
   • Soil core plants: 35 x 35 cm, 38 x 30 cm or 60 x 60 cm.
   • Budwood nursery: 90 x 60 cm or 120 x 60 cm

Nursery for seedlings and budded stumps

The nursery beds should always be kept free of weeds. Three rounds of weeding are needed. The first weeding is done just before application of the first dose of fertilizers and the second weeding before the second dose. The third round of weeding is done just before commencement of budding during May or June. The first round of manual weeding can be replaced with the application of pre-emergence herbicides. After the final preparation of the nursery beds, diuron at the rate of 2.5 kg per ha in 700 L water is sprayed on the beds and germinated seeds planted five days later.

Mulching is an important operation to be followed in seedling nurseries before the beginning of the summer season and after the second round of fertilizer application. Natural materials such as tree loppings, dry leaves, undergrowth from forests, grass cuttings and cut cover crop material are commonly used after they are dried. A single round of good mulching in December is adequate. Black polythene sheets properly anchored to the soil to prevent them from being blown away by wind can also be used for mulching. Spreading a thin layer of soil above the sheet is an effective way to achieve this.

During the dry period, which usually extends from December to April, the nurseries should be irrigated. In large nurseries, overhead sprinkler irrigation systems are ideal. Daily watering is preferred during the initial weeks. Later, the frequency of irrigation can be reduced to once in two or three days.

Budwood nursery

Buds required for budgrafting are collected from budwood obtained from plants raised specifically for this purpose.

Budwood nurseries are of two types:

1. Brown budwood nursery (produces brown buds)
2. Green budwood nursery (produces green buds)

After cleaning and levelling, soil is first dug to a depth of 45-60 cm. Planting can be done with polybag plants, budded stumps or seed at stake followed by budding. For green bud shoot nursery the spacing is 1 m x 1 m or 80 cm x 90 cm. Proper fertilizer application may be carried out to ensure good growth. Other agronomic practices such as irrigation, mulching, weeding, shading, protection against diseases and pests are followed in a similar manner as for seedling nursery.

During the first year of planting, only one shoot is allowed to grow. About 1 m of brown budwood can be obtained from this after one year.

From the second year, two or three shoots are allowed to develop on a plant depending on the spacing adopted. To remove the leaves present in the brown-coloured budwood, the leaflets are first removed by clipping the tip of the leaf stalk. After about one week, the leaf stalk dries and falls off.

Budwood is then harvested by sawing off, leaving about 15 cm at the base. From this portion shoots develop in the subsequent season.

Green bud shoot plants are shaped from brown budwood plants. For this, a well-established brown budwood plant is first cut back at a height of about 75 cm. A number of shoots emerge below the cut end. Among these, only 3-5 most vigorous ones are retained and the rest removed. When these shoots have grown and produced brown wood to a length of about 5 cm, they are pruned at the point where the brown colour ends so as to produce more branches. Two to three most vigorous branches are retained on each shoot and the others cut off. When these secondary branches develop brown colour at the basal 5 cm, they are again pruned. New branches arise from these and give the budwood plant a bushy appearance. For producing green shoots, all the branches of a green bud shoot plant (also called source bush) are pruned. The new branches arising are harvested when one whorl of leaves develop. The harvested budwood is cut into pieces of convenient length before being taken to the nursery beds for budding.

Polybag nursery

Planting materials in polybags can be prepared by two different methods.

1. Budded stumps can be planted in polybag and the scion allowed to develop till they are ready for planting in the field.
2. Germinated seeds are planted in polybags and bud-grafted when 5-6 month old.

The roots of budded stumps can be treated with indole butyric acid (IBA), a hormone that enhances root growth. Dipping root in cow dung slurry before planting enhances root development.

Planting in polybags

Polythene bags of lay-flat dimension 55-60 cm length and 25-30 cm width which can hold about 8-10 kg soil, are usually used for raising plants up to two to three whorl stage. For producing plants of 6-7 whorls, larger bags of 65 cm x 35 cm size and holding about 23 kg soil should be used.

In order to facilitate drainage, sufficient number of holes should be punched on the lower half of the bags. Low density polyethylene (LDPE) sheet of 400 gauge and 500 gauge thickness are usually used for making small bags and large bags respectively. Bags made of high density polyethylene (HDPE) sheets can also be used for this purpose. However, such bags are likely to deteriorate when exposed to sunlight for long periods.

Soils with clay-loam texture, good structure and friability are ideal for this purpose. The fertile topsoil collected after removing the surface vegetation and leaf litter is ideal for filling the bags. While filling, the bag should be gently tapped to ensure compact filling of soil without leaving air spaces. The bag is filled up to about 2 cm below the brim.

Powdered rock phosphate at the rate of 25 g for small bags and 75 g for large bags is mixed with the top layer of soil. The filled bags can be kept in the nursery either in trenches or on the ground supported with wooden poles. After placing the bag in the trench, the excavated soil is filled in the gap between them. The remaining soil is mounted around the bags.

Planting of budded stumps or sprouted seeds is undertaken thereafter. When budded stumps are used, the bud patch should face the footpaths to facilitate growth of sprouts.

Regular cultural operations like manuring, watering, weeding, shading and plant protection are adopted. Application of N-P-K-Mg 10-10-4-1.5 mixture is done at monthly intervals. During the first month, 10 g of the mixture is given per bag which is gradually increased to 30 g in four months time.

Watering should be done soon after manuring. During dry periods, irrigation should be done regularly. Watering can be done manually in small nurseries while sprinklers or drip irrigation system is more economical in large nurseries. Too much watering should be avoided to prevent waterlogging. During summer months, partial shade may be provided to the plants by erecting overhead shade. Appropriate prophylactic and curative measures may be taken against diseases and pests.

Advantages:

1. Contribute to reduction in immaturity period
2. Help to achieve a uniform stand; useful for vacancy filling and late planting.

Last updated: 24-05-2008