Stevia is a perennial herb. Stevia is known all over the world due to its sweet leaves and zero caloric. Stevia leaves contain sweetening compounds.
Sweetening compounds (glycosides) namely Rebaudioside A, B, C, Stevioside and six other compounds which have insulin balancing properties. Naturally occurrence of stevia is in Paraguay and Barazil. But now a days stevia is cultivated all over the world.
It is an annual plant which may be one meter long. The length of leaves are 2 to 10 cm. Its leaves are 10 to 15 times sweeter than table sugar and its stevioside is 200 to 300 times sweeter than table sugar. Stevioside recovery from stevia leaves is 10% and from branches is 2 to 3%.
Stevia can adapt a wide range of climate. It requires a range of temperature -60C to +460C and rain fall between 1500mm to 1800mm. Plants grown at higher latitudes have a higher percentage of sweet glycosides. Long days favor leaf growth and short days trigger blossoming. Day length is more critical than light intensity.
Two cuttings can be gain from stevia in a year. Its per acre profit is many times greater than other one year crop layout like wheat+cotton and wheat+rice.
Analyzing dry leaves of stevia has shown that it is full of nutrients. If we analyze 100g dry leaves of stevia then it will contain following concentration of different nutrients:
|Sr no.||Ingredients||Quantity (g)|
Time and Method of Cultivation
We prepare nursery for stevia cultivation. Nursery can be prepare from seed, propagules and tissue culture. Seed nursery can be transplanted after 2 months and propagule and tissue culture nursery can be transplanted to field after 1 month.
For spring cultivation, nursery grow in November and transplanted to field in February.
Methods for Stevia Nursery Raising
We will discuss three methods as follow:
- Through Seed
1- Nursery preparation in plastic cups
Growth rate of stevia seed is very low. Growth rate of black and dark brown seeds is very good. For seed sowing we can use plastic cups and plastic envelops. Pour 2 to 3 seeds in every cup with thin soil layer and spray water.
After that apply water according to requirement of Seeds will grow within 1 to 2 weeks. Cover the seeds with plastic sheet to conserve moisture. One gram seed nursery of stevia is enough for 5 marlas because stevia seeds are very small and lightweight. 1000 to 1500 plants can be prepare from one gram seeds.
2- Nursery Raising on land
For one acre 30 to 35 grams seed require. After making fine and leveled soil mix rotten farm yard manure in soil then fall seeds equally on soil. Cover these seeds with thin soil layer. It should be remember that irrigate the sown seeds with sprinkler rather flooding the plot.
Cover them with plastic sheet to conserve moisture. Lightly spray water until 5 to 6 days at morning. When seed germination complete within 6-7 days then cover them at night time and uncover them at day time. In this way nursery will be ready to transplant about 6 to 8 weeks.
- Nursery Raising by Propagules / Cuttings
Cut the 4 inches part of the upper site of stevia put it in the plastic cup and spray water. Important thing is that it should be 1-2 inches below the soil surface. Cover the whole propagules with plastic sheet and transplant them into field after preparation. Put out plants after 15 days then put them under shade for 10-15 days. To doing this environmental resistance of plants become increase.
- Through Tissue Culture
Prepare Murashige and skoog meidium (MS Media),sterilize it at 1210C for 20 minutes. Use Naphthalene acetic acid(NAA) or Indole-3-butyric acid(IBA) for roots and 6-Benzylaminopurine(BAP) or Kinetin for shoot growth. Clean the 2-3cm long pieces of branches with 70% Ethanole Surfactants and water then to go in Flow Laminar to wash them with 5% sodium hypochloride, 0.1% mercuric chloride and sterilized water.
Pour the bud part of the branches in test tube and put them in growth room at 250C for 16 hours light and 8 hours dark per day. Then transfer plants form test tube to plastic cups. For 20 days put them at 280C and 70-90% moisture. So, plants will capable to transplant into field.
Stevia requires soils which have good drainage properties. Soils which have moisture content for long time are not suitable and black cotton soils with very heavy clay content should also be avoided. Red soil and sandy loam with pH of 6-7 are best for stevia cultivation. Saline soils with pH more than 8 are unsuitable for stevia.
Loamy soils are more suitable for stevia cultivation. The land should be ploughed initially 2-3 times with harrowed or disc plough to break the clods with 2 plankings to fine the soil.
Farm Yard Manure
During the land preparation pour the 8-10 tralies of rotten farm yard manure 2-3 months before the sowing. If rotten farm yard manure is not available then use the green manuring.
Crop is grown on raised beds because intercultural operations are easily handled by manual labor. Raised bed should be of 15cm in height.
After 15 days put out the plants from plastic envelops/sheet and put them under shade for 10-15 days to increase their environmental resistance. We should completely prepare the soil before transplanting.
Make ridges by thoroughly mixing the manure, DAP and potash. Maintain plant to plant distance 30cm and row to row distance 45cm. Light irrigation done after transplantation.
According to weather and soil conditions 1-2 light irrigation’s should be done in a week. It is necessary to apply light irrigation during summer season because more water can cause muggy (Suffocation) at evening. Due to this lower leaves of plants become yellow and the attack of fungus diseases becomes more.
Use 2 bags of urea, 1 bag DAP and 1bag potassium sulfate per acre for good production.
Stevia requires hoeing and weeding. Manually removal of weeds are more preferable because its leaves use directly or indirectly for eating purpose. First weeding or hoeing done after 15 days and subsequent hoeing and weeding will be done one month after the first weeding and hoeing. Hoeing is also required immediately after harvesting.
Insects and their Control
Insects of stevia are termites, aphid, jassid, thrips and army worm but these do not cause serious or more damage. However, control becomes necessary for insects which cause more damage. But we should avoid the use of pesticides on stevia.
Diseases and their Control
Root rot disease in stevia. In this plant starts becoming yellow from bottom to upper site and completely dry. It’s attack is more at initial stages. It spread through fungus which presents already in soil. Roots of diseased plant become spoil and easily break. Mix 400g Topsin-M in 100 liter water and spray around the roots to control the root rot disease.
It is done by cutting the growing tips of stevia plants every 2-3 weeks for the first month. This practice is done to encourage new and bushy growth, produce dense foliage and promote healthy growth. During pinching the buds and one pairs of leaves are removed by clean and sharp cutters. It helps to prevent breakage of stems during high winds.
First harvesting after 4 months and subsequent after every 3 months OR harvest the leaves before flowering because sweetness is more in leaves before flowering. If we want to separate leaves after harvesting then harvest it 2-3 inches from soil surface. In this ways the plant can grow their new branches again.
Threshing is necessary to separate dry stevia leaves from its stem. To separate impurities the powdered stevia leaves should be sieved with 2-3cm sized sieves. Avoid the mixing of stevia leaves with other crop or weed leaves this may deteriorate the quality of stevia leaves.
Method of Dry
Immediately after harvest the herb is dried. Put the leaves in shade for dry after thoroughly wash. It can also be dried using simple drying racks inside transparent poly house or by passing dry air just above room temperature.
From 2 cuttings 40-45 mounds of dry leaves per acre can be obtain.
Dry leaves are stored in plastic lined cardboard boxes, sealed, strapped and labeled for further processing.
Method of Use
Dry leaves may be use such as dry leaves or in powder form. Stevia leaves powder of 250mg is sufficient to sweet one cup of tea. So, by this 4 cups of tea can be make from 1 gram of leaves powder. Quantity of leaves may be add in every meal according to taste.
Types of stevia products
- Fresh stevia leaves
- Dried stevia leaves
- Stevia extracts
- Liquid concentrates
- Regulates blood pressure
- Control blood sugar and Insulin levels
- Due to zero calories it is control diabetes
- Weight loss
- Prevents cancer
- Lowers cholesterol level
- Use as additive for toothpaste because it reduce bacterial formation
- Useful for skin care
- Prevents osteoporosis
- Anti-diarrheal, anti-fungal, anti-viral, anti-hyperglycemic, anti-hypertensive, anti-inflammatory etc.
- Use in mouth wash
- Strong blood vessels
- It’s extract is useful for dandruff.
- Zaratnama of 1 march 2019
- Stevia Production Guideline
Authors: Muhammad Sajjad*, Muhammad Umer Hameed, Faryal Ahmed
(University of Agriculture Faisalabad)