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Sci Tech
Perennial herb as natural sweetener
By Our Agriculture Correspondent
The sweet herb is 30 times sweeter than cane sugar but without any calories
A PERENNIAL herb originating from Paraguay has a lot of potential as a safe sweetening agent and this natural sweetener is extensively used in Japan. The sweet herb is botanically known as Stevia Rebaudiana, and it belongs to the family Compositae. "The leaves of Stevia have a sweet taste, which is 30 times that of cane sugar, but surprisingly without any calories," explains Dr. N. Barathi, a horticultural expert and tissue-culture specialist from Hosur, Tamil Nadu. "Stevia is the safest natural sweetener, and it can substitute cane sugar in various preparations and formulations. It has been used to treat many ailments including diabetes, high blood pressure, digestive disorders, addictions and several skin defects," says Dr. Barathi.
Stevia can be grown easily in pots, house gardens or as a commercial field crop. The plant reaches a height of about 45 cm in three months. Since it is a short-day, its sweetening potential increases when it is grown under long day. It prefers a well-drained light soil such as red soil and sandy loam.
The field should be well worked to bring the soil to a fine tilth before planting. Liberal application of ripe farmyard manure would prove to be highly beneficial. A spacing of 25 cm x 60 cm is recommended for its cultivation, and it ensures a cropping density of 75,000 plants in a hectare, according to Dr. Barathi.
As it cannot stand drought, Stevia needs regular irrigation. The irrigation schedule should be worked out based on the soil type, light intensity and prevailing wind conditions. The ideal condition for the plants to grow luxuriantly is 50,000-60,000 lux of sunlight for more than 12 hours a day with temperatures hovering between 25 and 35{+0} C.
The night temperature should not fall below 10{+0} C. A region with low wind velocity, and assured water resources suits this plant well, according to him.
The first harvest of crop can be had in four to five months after planting. Subsequent harvests can be had once every three months for up to three years after planting. The sweetener in the leaf is found to be more till the plant flowers.
So it is better to cut the plants leaving about 10 cm stem portion from the ground. This will facilitate new flushes to emerge, which can be harvested as the next crop. The freshly harvested plants are hung upside down and dried in shade. It can also be dried using simple dryers using dry air just above room temperature. Drying is a critical factor, as protracted drying will lower the Stevioside (the sweetening agent) content of the leaves.
After adequate drying, the leaves are stripped of the twigs and packed and stored in cool, dry places.
The crop, when managed well, will yield about 6750 kg dried leaves per hectare in four harvests in the first year.
The cost of cultivation of this sweet herb in the first year is about Rs. 10 lakhs per hectare, and it will be about Rs 1.87 lakhs in the subsequent years.
The gross income from the crop (at a market price of Rs. 200 per kg dry leaves) will be about Rs. 13.65 lakhs, according to Dr. Barathi.
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