Manuring the seedling nurseries
Two and a half tonnes of compost or well-rotten cattle manure and 350kg powdered rock phosphate for every effective hectare may be incorporated to the nursery bed as a basal dressing. If the same beds are used repeatedly, application of rock phosphate is needed only once in three years. If the nursery is established in a newly cleared forest area, compost or cattle manure is not necessary during the first year and rock phosphate alone is sufficient.
Spacing varies according to the type of planting material to be raised in the nursery. If the nurseries are laid for brown budded stumps, the common spacings adopted are 30´30cm (12”´12”) or staggered pairs of rows 60cm apart and 23cm between plants (24”´9”). To provide green-budded stumps 23 x 23 cm spacing is ideal. For bud wood nurseries a planting distance of 60´90cm (24” ´36”) or 60´120cm (24”´48”) with wider spacing between rows is to be adopted.
If weather is favourable, planting can be carried out during this month also. The lateral roots of the budded stumps should not be trimmed too close to the tap root since these roots are vital for the early establishment and growth of young rubber plants. Lateral roots may be trimmed about 7.5 to 10cm from the tap root. The stumps having more than one or twisted tap roots should not be used for field planting.
The stock of the budded stumps should be cut back at a height of about 7.5cm above the bud patch. The cut may be with a downward slant from the side of the bud to the opposite side.
About 5cm of the surface soil is first removed from an adequate area around the planting points to accommodate the lateral roots. A planting cavity is then made with an alavango to a depth equal to the length of the tap root.
The budded stumps can be planted now by inserting the tap root into the planting cavity. The tip of the tap root is to be in actual contact with the soil at the bottom of the cavity. After keeping the lateral roots in position in the area dug, loose soil may be put in the cavity around the tap root and pressed firmly. This is best done by pushing the alavango into the edge of the planting hole as deep as the tap root is, in a slanting manner so that the top part of the alavango is away from the stump and the lower end near the tip of the tap root and then pulling it strongly towards the stump which is firmly held in position. This process is repeated on all sides, without causing any damage to the bud.
If polybag plants are used, the top storey of the leaves should be mature at the time of planting. The lateral roots and tap root if grown out of the bags may be dressed before planting in field.
For the proper growth and establishment of cover crops in plantations, monthly removal of weeds in and around the patches for four to five months is necessary. Application of 150 kg of powdered-rock phosphate per hectare in two equal installments is recommended. In areas where the soils are deficient in potassium, application of a mixture of 150 kg of rock phosphate and 50 kg of Muriate of potash may be used. The wild legume, Mucuna bracteata, which grows very fast and is not eaten by cattle can also be used as cover crop.
Weeding should be carried out by adopting either manual methods or by use of herbicides in the rubber plantations. The weeds removed manually may be kept in plant rows which when dried can be used for mulching the plant base. Cover crop should not be allowed to grow in a circle of about 6 feet diameter around the plants or along the terraces for 3-4 years to prevent competition with the young rubber.
Spraying Bordeaux mixture (1%) may be carried out at fortnightly intervals to protect young plants in the nursery as well as in the field against shoot root disease. Periodic inspection for detecting pink disease affected plants may be undertaken on sunny days as the disease is prevalent during southwest monsoon period. The disease is more damaging to clones RRII 105 and PB 217. The main seat of infection is usually the fork region. Initially white or pink coloured cobweb mycelial growth on the bark surface may appear with streaks of latex oozing out from the lesions. Rotting, drying up and cracking of the affected bark will follow. In the early stages of infection Bordeaux paste has to be applied on the infected parts and 30 cm above and below the affected areas. When the infection is in its advanced stage cracks are formed in the bark and exudation of latex occurs. In such cases Bordeaux paste may be applied initially and after drying, the affected region may be scraped to remove all the rotting bark and mycelium and then the paste is applied again as done earlier. Dried branches after disinfection should be pruned off and burnt. Application of fungicides like Thiride was found effective in containing the disease when incorporated (10g/kg) in a petroleum wound dressing compound.
If tapping is continued during the rainy season use of an effective panel protectant is essential to protect the tapping panel from bark rot which may occur during the season. If any leakage is found in the rainguards it should be rectified and if necessary it may be replaced with new ones.
Fungicide like Indofil M-45/Dithane M-45 (5 gm/l of water) or Akomin/Phosjet (2ml/litre) may be applied at weekly intervals on the tapping cut against bark rot disease.
In trees where the infection is advanced and the panel is rotten, the surface may be scraped to remove the decaying tissues and washed with effective fungicide solution and then any of the wound dressing compounds like Rubberkot, Sopkot, Treseal etc. may be applied to the panel. During rainy season, application of a panel protectant like Rubberkot or Sopkot, at monthly intervals may be made to avoid excessive moisture.
Incidence of patch canker is also noticed during rainy season. The affected area may be cleaned by removing the coagulated pad and rotten bark, washed with Indofil M-45/Dithane M– 45 (10g/litre of water) and applied with any wound dressing compounds.
During the initial years of growth some plants show a tendency for severe bending . Heavy canopy tends to bend in wind and even break during rains. In such cases the plants have to be pulled erect by providing adequate support. The broken trunk or branches may be dressed and washed with fungicide solution and applied with a wound dressing compound.