Stevia product has been an alternative sweetener in Japan for many decade as a dietary food. It has been banned in USA in 1990's due to the national regulation. The sweetness of stevia are due to the chemical content of steviol glycocide that has 300 times sweeter compare to sugar. Chine nowadays is the largest stevia producers in the world in planting size and end product. Other countries seriously grow stevia are Thailand, Vietnam, Malaysia, Korea, Taiwan, Uruguay and Malaysia. As I check with DOA Malaysia there is no official record of stevia planted acreage in Malaysia in 2010 but I estimate about 50-60 hectare mostly grown in Pahang, Selangor and Perak. The climate and rainfall in Malaysia are suitable for stevia to be grown commercially as profitable ventures. Few companies started to grow and market their product as dietary and supplementary food for diabetic patient, obesity and high blood problem.
As a transplanted annual plant, stevia tends to grow well on a variety of soil types ranging from course textured sands to well drained loams but not clay or poorly drained sites. The selected area must has a very good drainage system and enough water supply. The shrub like stevia need full sunlight for maximum growth rate. During the growing season, it seems to thrive in a temperature range of 15°C to 30°C provided all input resources and good management practices are incorporated. Stevia requires cultivation practices similar to those of other transplanted horticultural crops. Educated and experience vegetable farmers in Malaysia has no problem with growing stevia provided there are a stable marketing system and acceptable price for best quality. Until I write this article the demand for stevia are uncertain due to lack of consumers demand.
Report from research confirm that stevia leaves have a long history of use as sweeteners, due to the presence of sweet crystalline glycosides called steviosides which are 200-300 times sweeter than sucrose. Stevioside is non-caloric, non-fermentable, non-discolouring, heat stable at 95°C and has a lengthy shelf life. The product can be added to cooked or baked goods or processed foods and beverages. In the Pacific Rim countries, China, Korea and Japan, stevia is regularly used in preparation of food and pharmaceutical products. There are better future markets for stevia with the increase in consumer purchasing power in dietary health food especially in China and many ASEAN countries. Lets go to the technology in stevia planting based on my observation in Pahang and Selangor and from few references in the web.
Agronomic Practices of STEVIA
1. Climatic Range
Stevia is native to semi-humid, sub-tropical climates where temperatures typically range from -6 Celsius to 43 Celsius. Malaysia and most ASEAN Country are the best place to grow stevia all year round. While tolerant of mild frost, hard frosts will kill the roots of the plant therefore in temperate country they has chance to grow stevia compare to our beloved Malaysia. The best area for stevia may located at central region of Peninsular Malaysia, Sarawak and Sabah.
Stevia grows well on infertile, acid soils, but can also be cultivated on more neutral soils (pH6.5-7.5). Stevia will not grow in saline soils. There is a claim by my corlicks in Pontian growing stevia on medium deep peat soil with a very good harvest last year. The mineral soil with excellent drainage system and fertile is the best alternative for stevia plantation.
3. Land Preparation
Fields should be plowed and either disced and/or cultivated twice to prepare a fairly smooth, firm planting surface. Add some organic fertilizer such as processed chicken dung or other manure to increase soil fertility. The flat area should be ridged to allow better water flow during raining season. Make a low bed in the farm for proper agronomic practices.
Transplants from cuttings would be superior, however the cost is prohibitive. Stevia must be propagated from seed in plug trays placed in a greenhouse for a period of 7 to 8 weeks. The certified seed from authorised seller used for best stevia seedling. Put single seed in seeding tray (102 or 78 holes) which contain cocopeat as the germination media. Watered accordingly and transplant individually in morning or late afternoon.
Planting of stevia by plug the seedling planted into the field on either 53 cm or 61 cm row spacing with a total plant density in the order of 100,000 plants/ha. Ensure the seedling in a good row and even planting distance. Watering are critical in initial growing stage by using automatic sprinkler system or drip tape irrigation system. The spraying of pre-emergence before planting are recommended with LASSO or other chemical weeks before transplanting. There is few aggressive farmers using silvershine plastic cover on the bed for stevia planting.
The plant appears to have low nutrient requirements, however a soil test should be conducted. For the year 1995, test plots were fertilized with 100 kg/ha of 6-24-24 prior to planting and a split application of urea at 140 kg/ha. The use of organic fertilizer at the initial stage are good practices in Malaysia especially on low soil fertility level. There are report that the use of foliar fertilizer to stevia at for the matured tree affect the sweetness of the leaves.
Normally, the stevia plant requires frequent, shallow irrigation. Generally, irrigation is required when the stem tips begin drooping. Therefore stevia farmers in Malaysia must include irrigation cost for long term investment. Ponds, river or canal as source of water with sprinkler or drip tape system may suitable for stevia.
7. Weed Control
Repeated mechanical row-cultivating can be used to control weeds. The crop may also require hand hoeing and weeding. Chemical control for weed are and options and farmers should not use weedicide freely because it will affect the leaves if not properly used.
8. Pests and diseases
Insect pest pressures other than cutworm are minimal. Septoria disease caused considerable damage to the over-mature 1995 crop. Chemical control for stevia pests should minimised or use IPM method to overcome damage by pests attack. There is a report oversea that browsing by deer, who seem to like the sweet taste of stevia, may also be a problem especially if the farm located to the jungle where the deer are there. There is no serious disease reported in Malaysia. Only minor pests and disease problem in stevia planting and manually pull-out the affected tree and removed.
Time of harvesting depends on variety and growing season either wet or dry season in Malaysia. Harvesting has to be arranged according to production calendar when plants are 40-60 cm in height. The uniform average height may be achieved with proper Good Agronomics Practices. There is a report that shorter days induce flowering in temperate country but not significant in Malaysia. Optimum yield (biomass) and stevioside quality and quantity are best just prior to flowering. Ensure the is enough manpower for harvesting activity to cut, gather and process the stevia plants. The plant will tolerate temperatures. Specialized harvesters may need to be fabricated to mechanize the harvesting process. Grading of leaves may necessary if you want to sell the stevia fresh leaf to niche consumer.
Drying of the woody stems and soft green leaf material is completed immediately after harvesting utilising a drying wagon or a kiln. Depending on weather conditions and density of loading, it generally takes 24 to 48 hours to dry stevia at 40°C to 50°C. An estimated 21,500 kg/ha of green weight is dried down to 6,000 kg/ha of dry weight. The production of stevia in Malaysia reported about 18 mt wet leaves/stem per hectare in Pahang last year. This is considered a acceptable harvest of stevia in Malaysia.
Immediately following drying, a specially designed thresher/separator is necessary to separate dry stevia leaves from the stem. The yield of dry stem and dry leaf is similar at approximately 3,000 kg/ha each. The stem are collected and processed for their content.
Dry leaves are stored in plastic lined cardboard boxes, sealed, strapped and labelled for further processing. If the farmers want to sell the dry leaves just sent to local marketeers. The best system is to engage with 'anchor company' so there is a guarantee market and payment. The labeling system by grade is applicable.
13. Economics of Production
Recent cost of production data for Malaysia is not available, but research from few growers indicates that sample leaf yields taken at the optimum harvest period have a yield potential of 2,850 kg/ha (dry stevia). Cost of production for stevia has to be calculated. My visit to MAHA Exibition 2010 checked the end processed product from exhibitor's priced at RM 30-RM40.00 per packed (contain 250-400 g in sachets). There is more promotion the usage of stevia in Malaysia if we want to create more domestic demand. The best is to market stevia in global market especially claim as Organic Product from Malaysia. Farmers should apply Skim Organic Malaysia (SOM) or Farm Accreditation Scheme (SALM) in future.
Stevia is commercially produced in temperate regions (like China, Korea and Taiwan) and other par of the world where it can be grown as a perennial crop. For future Malaysia growers to be competitive with these other production regions, New stevia variety with high productivity should be introduced. . Other requirements that are needed to reduce the cost of production include further refinements in agronomic practices, plant breeding to improve yield and quality, development of mechanisation techniques in transplanting, harvesting, drying and threshing, and the registration of pest control products.
I hope this article able to provide knowledge the all of you. I would like to buy some stevia seed and grow in surrounding semi-D spacious compound in the pots. I think we can reduce the importation of sugar from overseas with promotion campaign to consume stevia and sugar. We need more agronomic technology, processing activity and create special marketing plan for stevia. Malaysia Boleh !