A Brief Summary of Stevia Cultivation
Stevia grows best in sub-tropical climate. Stevia plants needs rich garden soil, full sun and partly shade, humidity, high temperature, and plenty of water. Stevia Seeds are best sown in summer or in a warm greenhouse, and should be lightly pressed into the soil but Not covered with soil. The reason why it may not germinate if seeds are covered all over by soil. The stevia seeds need sunlight for the germination process. In Canada, it can be grown as an annual outdoors or year-round in a greenhouse.
The plant prefers a lightly textured, well-drained soil to which organic matter has been added. It needs ample water so that the soil is consistently moist, but not wet. In hot, sunny climates it will do best in semi-shade. Propagation is from seed sown in spring. Plant seedlings out once all danger of frost is over. Leaves are best harvested just before flowering. The plants will also grow from cuttings, which are best taken in late winter. The concentration of stevioside in the leaves of Stevia increasing when the plants are grown under long day condition.
While, cultivating stevia on a large scale, it can be grown in well-drained red soil and sandy loam soil. The soil should be in the pH range of 6.5-7.5. Saline soils should be avoided to cultivate this plant. Since seed germination rate is sometimes poor, it is propagated vegetatively. Though stem cuttings are used for vegetative tissue culture plants have proven to be the best planting material for Stevia. Tissue culture plants of Stevia are genetically pure, free from pathogens and have excellent vigour. The tissue culture plants can be planted throughout the year, except during peak summer. An ideal planting density is approximately 40,000 plants per acre with spacing of 30x60 cm in a raised bed system. The soil can be enriched with a basal dressing of 25 tons of well rotten farmyard manure/hectare.
Land preparation:
Land should be ploughed initially with a disc plough or harrowed to break down the colds. Fine tilth is required. One to two times ploughing has to be done after harrowing. Around 25 MT of FYM/Ac has to be applied as a basal dressing during the last ploughing to incorporate the manure with soil.
Soil Type:
Stevia requires very good drainage. Any soil that retain the moisture for very long period of time are unsuitable for Stevia cultivation and should be religiously avoided. Similarly black cotton soils with very heavy clay content should also be avoided. It is mandatory that before planting, each and every soil sample should be properly tested and analyzed by an expert. Red soil and sandy loam with a 6-7 pH are best for the cultivation of Stevia.
Raised bed preparation:
Forming raised beds is the most economical way to grow Stevia. The raised bed should be of 15 cm in height and 60 cm in width. The distance between each plant 23 cm. This would give a plant population of around 30,000 per acre.
Planting:
Stevia can be planted in many ways. The types of agronomic practices generally depend on type of soil and climate conditions. Generally it is advisable to plant minimum of 40,000 plants per acre. Since the economical part is the leaves it is very important to achieve highest vegetative growth.
Planting Material:
There are basically three options for multiplication. The first is the seeds, second the tissue culture and third the stem cutting.
Stevia propagation through seeds was once considered unrealistic due to poor seed germination and the lack of identical plants. However, with new varieties that have high germination rates and the experience gained in successful seed nurseries, seed propagation has become an important method of multiplying stevia populations. All stevia varieties in the market are open-poll, making seed propagation a viable option for growers.
Stevia can be propagated through cuttings, with one plant producing up to 50 identical cuttings. However, stem cuttings require more facilities and experience, making it more expensive than seed propagation.
Tissue culture is a successful method for growing Stevia tissues in artificial media. It's the fastest way to multiply Stevia plants, and all produced plants are identical. However, cost is the main factor affecting the decision to use this method. Big labs offer better prices and a greater number of plantlets, but produced plantlets need acclimation in special greenhouses.
Plant Varieties:
There are about 90 varieties of stevia rebaudiana developed all around the world. Basically all these varieties have been developed for different climate requirements, many times these varieties perform strangely in different climate conditions. In recent year, with new varieties that have seeds with high germination rates and since all stevia varieties in the market are open pollinated varieties along with better experience with successful seed nursery, seed propagation became an important method of multiplying stevia population. At the end of the day, just like sugarcane, it is the stevioside and rebaudioside content in the Stevia leaves that determine the price and marketability of Stevia leaves. Nowadays, several varieties can have Reb-A content up to 80% of the total stevioside glycoside, with very little bitterness and aftertaste.
Irrigation:
Stevia requires ample supply of good water all year around. As the plant cannot tolerate drought, frequent irrigation is required Micro sprinklers are the best method of irrigation would not supply the required amount of water at the right time.
So through micro sprinklers, the water can be sprinklers, the water can be sprinkled once in a day in winter and two to four times in a day in summer depending upon the heat and relative humidity in the air. Watering frequency should be scheduled so that the plants do no wilt for want of water.
Fertilizer application:
The recommended dose of fertilizer is 110:45:45 NPK/ac. This requires 4½ bags of urea, 2 bags of DAP and 2 bags of Potash. The entire dose of DAP is applied as the basal dressing. The Nitrogen and Potash fertilizer can be split and applied as 10 doses in every month. Nitrogen application is a must for the production of dry matters.
Plant protection:
Organic gardeners in particular should find stevia an ideal addition to their yield. Though nontoxic, stevia plants have been found to have insect-repelling tendencies. Their very sweetness, in fact, may be a kind of natural defense mechanism against aphids and other bugs that find it not to their taste. Perhaps that’s why crop-devouring grasshoppers have been reported to bypass stevia under cultivation. In case any disease symptoms are noticed, spraying of neem oil diluted in water is the best organic method.
Weeding:
Removal of weeds can be done manually. Since the crop is grown in raised beds, intercultural operations are easier by manual labour.
Maintenance:
Stevia plants do best in a rich, loamy soil-the same kind in which common garden-variety plants thrive. Since the feeder roots tend to be quite near the surface, it is good idea to add compost for extra nutrients if the soil in your area is sandy. Besides being sensitive to cold during their development stage, the roots can be also be adversely affected by excessive levels of moisture. So take care not to over-water them and to make sure the soil in which they are planted drains easily and isn’t soggy or subject to flooding. Frequent light watering is recommended during the summer months. Adding a layer of compost or your favorite mulch around each Stevia plant will help keep the shallow feeder roots from drying out. Stevia plants respond well to fertilizers with lower nitrogen content than the fertilizer’s phosphoric acid or potash content. Most organic fertilizers would work well, since they release nitrogen slowly. Flowering of the plant should be avoided. Since Stevia has a significant apical dominance, the plant tends to grow tall and lanky. Pinching of the apical bud would enhance bushy growth of the plant with side branches.
Harvesting:
Depending on climate conditions one can achieve the yields of 2000-4000 Kilos in three to six harvests annually. Another important aspect of harvesting is the timing of harvest. It should be noted that at no point of time plants should be allowed to flower since after flowering the Stevioside percentage goes down rapidly and leaves are rendered unmarketable. Leaves are harvested by plucking in a small quantity, or the entire plant with the side branches is cut leaving 10 to 15 cm from the base. The first harvesting can be done four to five months after planting. Subsequent harvesting can be done every three months, for three consecutive years. The sweetener in the leaf is maximum till the plant flowers. Just before flowering, the plant should be cut completely leaving 10 cm from the ground. The new flush of leaves will sprout from here. The new plant will be ready for harvest again in three months. The plant yields around 3000 kg of dried leaves from an acre of plantation every year. Harvesting should be done as late as possible, since cool autumn temperatures and shorter days tend to intensify the sweetness of the plants as they evolve into a reproductive state.
Unlocking the sweetness in your harvest:
Once all leaves have been harvested it’s required to dry them. This can be accomplished on a net. The drying process is not one that requires excessive heat; more important is good air circulation. On a moderately warm fall day, stevia crop can be quick dried in the full sun in about 12 hours. (Drying times longer than that will lower the stevioside content of the final product.) Crushing the dried leaves is the final step in releasing stevia’s sweetening power. The dried leaves are powdered, sieved and the fine powder is stored in containers. This can be done either by hand or, for greater effect, in a coffee grinder or in a special blender for herbs.
Seed Saving:
Stevia goes to seed late in autumn its first season. Seed heads are fluffy and light, and need to be grabbed before they are blown or washed away.
To buy stevia seeds visit: Clean Stevia Seeds