MEDICINAL AND AROMATIC CROPS (2+1)

Cultivation

Soil
Tuberose can be grown on wide variety of soils from light, sandy loam to a clay loam. The soil should be at least 45 cm deep, well drained, friable, rich in organic mater and nutrients with plenty of moisture in it. The soil should have a pH range from 6.5 to 7.5 with good aeration. The crop can be grown even in high saline-alkaline soils with better agronomical practices. It is observed that the vegeta¬tive growth and flowering are affected by increasing the levels of NaCl and very a low concentration of CaCI2.

Climate
The crop is best suited for cultivation in tropical to subtropical and temperate climates. The crop is reported to flower profusely through¬out the year, if the climate is mild and free from extremes of high and low temperature. A temperature range from 20-30°C is considered ideal for this crop. If the temperature is above 40°C, the spike length and quality of the flowers are affected. Very low temperature and frost will damage the plants and flowers. Tuberoses grow well in a sunny situation. Although the plant is photosensitive, exposure to a day-length of about 16 hours appreciably promotes vegetative growth and enhances the emergence of the first flower-spike by 10 days. The length of the flower-spike also increases under long days.

Season
Tuberoses are generally planted in February-March in the plains and April-May in the hills. The bulbs can also be planted during July-August. Tuberoses can be planted all year round in Bangalore, but a higher flower-yield is obtained from the April-May planting. To obtain flowers almost throughout the year, sequential planting can be practiced.

Land preparation
The land is ploughed deep, twice, to a depth of 45 cm. The first ploughing is done in January and the second about a month before planting. At the time of the second ploughing, 20-50 t/ha FYM is incorporated into the soil. Then the soil is brought to a fine tilth by breaking the clods and removing the weeds. The field is laid out into plots of convenient sizes with irrigation channels, ridges and furrows at the recommended spacing.

Propagation
Tuberoses are propagated by bulbs, bulb lets and seeds. Multiplication by bulb-segments and micro propagation from scale stem-sections is also possible. Propagation by bulbs is the most common method practiced for the commercial multiplication of tuberoses. The bulbs remain dormant during the winter months in places where the temperature is low and, if early planting is desired, the dormancy can be success¬fully broken by dipping the bulbs in 4% Thiourea solution for one hour. Ethylene chlorohydrin can also be used for breaking the dormancy.
The bulbs are separated from the clumps by rubbing off the loose scales and the long roots should also be removed. Spindle-shaped bulbs with a diameter of 2.6 to 3 cm size are used for planting. However, if the bulbs are very large they may be cut into 2-3 vertical sections, each containing a bud and part of the basal plate. Each of these sections is treated with copper fungicide and planted vertically with their tips just showing above the surface. About 8-9 t (1.0 to 1.5 lakhs) of bulbs are required to plant an area of one hectare.

Planting
The density of planting markedly influences the yield and quality of the flowers. The planting distance varies with the soil and climatic conditions. Spacing of 15 x 20 cm, (for Maharashtra), 25 x 25 cm (for West Bengal), 30 x 30 cm (for Lucknow), 30 x 22.5 cm (for Bangalore) and 20 x 20 cm (for South India) have been recommended for this crop. While planting, the bulbs are planted at the recommended plant-spacing, 3.5 cm deep on the sides of the ridges. The plots are irrigated immediately after planting.

Manure and fertilizers
Depending on the soil fertility, 20-30tonnes of FYM is applied. The neutral clay soils of Tamil Nadu the recommendation is 100 kg N and 60 kg P2O5/ha. For achieving increased essential oil content in flowers and for the maximum recovery of concrete, a fertilizer dose of 80 kg N, 60 kg P2O5 and 40 kg K2O/ha has been recommended. Of the full recommended dose of fertilizers, half the N, the full doses of P and K are applied at the time of planting and the remaining half of N is given as a top-dressing after 45 days of planting. Apart from N, P and K, calcium, magnesium, sulphur, iron, zinc, manganese, aluminium, boron and copper have also been found to influence the growth and flowering in tuberoses.

Irrigation
Irrigation is given immediately after planting. Subsequently, the crop is irrigated at 5-7 days intervals, taking into consideration the weather conditions. In the summer months, irrigation is recom¬mended twice a week.

Interculture
In order to keep the plots free of weeds and to avoid the exposure of bulbs, the plots are weeded and earthed-up once a month. Earthing-up enables the spikes to grow erect, despite strong winds and rains. The application of Atrazine (3 kglha) as a pre-emergent weedicide keeps the plots weed-free. A pre-emergent treatment of Gramaxone (3 kg/ha) followed by three post- emergent sprayings at intervals of 110 days in between the rows also keeps the crop weed¬ free. Mulching the plots with strips of black polythene, dried grass and chopped straw is effective in controlling weeds.

Growth regulators
The effects of pre-planting treatment of bulbs with GA3, ethrel or thiourea promoted early appearance of flower and the number of flower spikes but reduced the number of bulbs per plant. Treatment with GA3 (200ppm) produced highest number of longer spikes with maximum number of florets.