Botanical Names
Stevia rebaudiana Bertoni
Common Names
| Malaysia | Stevia. |
| English | Sweet herb of Paraguay, sweet honey leaf, sweet leaf, sugar leaf. |
| Indonesia | Stevia. |
| Thailand | Ya-wan. |
| Vietnam | Orngot. |
Family
Asteraceae
Introduction
‘Stevia’ originated from Paraguay and is well known for its natural sweetness, low in calories and free from carbohydrates, fats and proteins. The plant is new to Malaysia even though it is commercially cultivated in Brazil, Paraguay, United States of America and some Asian countries such as China, Japan, China, Korea and even Thailand.[1]
Morphological Features
‘Stevia’ is an erect growing plant and in Malaysia it can grow to 20-30 cm tall before it starts flowering. The leaves are green, developed in pairs measuring about 2.5-3.5 cm wide and 3-6 cm long. The flowers are white measuring about 8-15 mm in diametre and formed at the tip of the growing shoots. The mature seeds are black and very small (0.5–1.0 g/1,000 seeds). It has shallow but vigorous root systems.[1]
Medicinal Properties and Usage
The leaves contain rebaudioside A (R-A) and steviosides (St) which are 180-400 and 110-270 times sweeter respectively as compared to cane sugar. Thus, the plant is normally used as sweetener, an alternative to sugar for the diabetic patients and those on diet because of the very low calorie and no carbohydrates, fats or proteins. It is also reported to have antibacterial, antiviral and antifungal properties.[1][2][3][4][5]
Soil Suitability and Climatic Requirement
‘Stevia’ is highly adaptable and can be planted on various soil types. It is however more suited on loam and sandy loam soil with high organic matter content. The plant requires long days for maximum growth before it starts flowering. The critical sunshine hour is about 13 for maximum growth, biomass yield and thus the steviosides content. Under growing conditions with 13-16 daily sunshine hours, the crop can grow to 0.6–1.0 m tall before it starts flowering.[1]
Field Preparation
Land Preparation
Good field preparation is very important for good crop growth. This includes preparation of drainage system and field tillage. The recommended bed size is 120 cm wide with the working area of about 30 cm between the beds. The height of the bed is about 30 cm.[1]
Production of Planting Materials
The plant can be propagated either by using seeds, tissue culture or stem cuttings. The tissue culture plantlets are usually very expensive. Using seeds as planting materials is also not practical since it takes longer time (40-60 days) before it can be transplanted to the field. Stem cutting is the most practical since it is cheaper, easier and takes less time as compared to seeds or tissue culture technique. Choosing mother plants as source of cuttings is very important. Such plants should be at their vegetative growth stage (not yet flowering), vigorously growing and free from pest and disease infections. The cuttings should have 2-3 leaf internodes. The cuttings can either be raised in polybag or planting tray.[1][2]
Field Planting
The cuttings start to develop roots after 1-2 weeks of sowing and ready for field planting 4 weeks later. The recommended plant spacing is 20 cm within a row and 22 cm between rows. Each planting bed measuring 1.2 m can accommodate 5 rows. This will give the population density of about 166,000 plants/ha.[1][2]
Field Maintenance
Fertilisation
Both the organic and inorganic fertilisers should be used for good plant growth. The organic fertiliser such as processed chicken manure should be given as basal dressing at the rate of 0.5 t/ha by broadcasting before the beds are prepared. Both the compound (NPK=12:12:17:2+Te) and processed chicken manure are used as side dressing fertilisers. The first side dressing by using compound fertiliser at the rate of 0.5 t/ha should be given only after the second ratoon (harvest). The subsequent side dressing is given after each harvest by alternating the organic and compound fertiliser at the rate of 1.0 t/ha. These fertilisers are incorporated into the beds.[1][2]
Weed Control
Proper land preparation before planting is the key in controlling weeds in the field. Manual weeding while incorporating the side dressing fertilisers into the soil is an important practice for weed control. Planting at higher density (200,000 plants/ha) and organic mulching can also help to reduce weed problem in ‘stevia’.[1][2]
Water Management
Consistent water supply is important during the growth period. Water stress will reduce vegetative growth and early flowering. Sprinkler irrigation system is recommended since it is easy to maintain.[1]
Pest and Disease Control
‘Stevia’ does not have insect pest problem. The common diseases infecting ‘stevia’ are stem rot (caused by Rhizoctonia solani and Sclerotinia rolsii). Practising good agriculture practice can control Rhizoctonia solani.[1][2]
Harvesting
Harvesting is done when flower buds start to develop. At this stage, the vegetative growth starts to stop. The level of its bioactive content (steviosides) is reported highest at this stage. Harvesting is done by cutting the stem at about 5-10 cm above the soil level. The subsequent harvests are done at 30-35 days intervals. The potential yield is about 20-50 g/plant.[1][2]
Postharvest Handling
The plants should be dried once it is harvested. Delaying in drying can deteriorate the physical and chemical quality of the produce. The steviosides content is reduced almost by 33% in only three days without proper drying. Drying can be done either by using commercial drying ovens or sun drying. For good storage, the moisture content of dried ‘stevia’ should be less than 10%.[1]
Estimated Cost Of Production
The cost of production for a three year production period is about RM155,000. This includes the cost of land preparations, agriculture inputs and labour for crop maintenance, harvesting and postharvest handling activities. Based on the yield of about 11 t/ha/year (33 t/3 years), the production cost of dried ‘stevia’ is about RM4.69/kg. The production cost was estimated based on the cost of current inputs during writing of this article.[1]
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References
- Tan S.L., Wan Zaki W.M., Muhamad Ghawas, M, Mansor, P. and Zawawi M. 2010. Stevia (Stevia rebaudiana Bertoni). In Teknologi Penananaman dan Pemprosesan Primer Tumbuhan Ubatan (Musa, Y., Mansor, P., Yahaya, H., Wan Zaki, W.M. and Aini, Z. editor).
- Muhammad Ghawas, M., Wan Zaki W.M. Zawayi, M., Mansor, M. and Muhammad Azhar A. B. (2009). Penanaman dan pengeluaran tanaman stevia. Bull. Teknol. Tanaman Bil. 6
- Crammer, B. dan Ikan, R. (1986). Sweet glycosides from the stevia plant. Chemistry in Britain. 22(10): 915-7
- Tan, S.L., Muhammad Ghawas, M., Mohamad Najib, M. Y. and Zawayi, M. (2008). Preliminary selections of stevia (Stevia rebaudiana Bertoni) under Malaysian conditions. J. Trop. Agric. and Fd. Sc. 36 (2).
- Chang, S.S. dan Cook, J.M. (1983). Stability studies of stevioside and rebaudioside A in carbonated beverages. J. Agric. Food Chem. 31: 409-12
