Cultivating Stevia

Stevia’s incredible natural sweetness has spurred its cultivation around the world. Growing stevia requires a lot of work, not to mention some help from mother earth, sun and rain. For industrial scale cultivation it is plant genetics along with their adaptation to their environment (climate and disease control) that will determine the quality and quantity of leaf production. Irrigation is required to ensure good biomass production. Disease prevention along with controlling flowering in areas centered around the equator may be the greatest challenge. Click on the tabs below to get a general idea of what is involved when growing high quality stevia leaf:

  • 1.0 *** Environment & Climate:
  • 1.1 Climate
  • 1.2 Humidity
  • 1.3 Latitude
  • 2.0 *** Water and Irrigation:
  • 2.1 Plant Water Requirements
  • 2.2 Access to Water
  • 2.3 Irrigation
  • 3.0 *** Soil & Land
  • 3.1 Soil
  • 3.2 Field Design
  • 3.3 Levelness and Firmness
  • 3.4 Raised Beds
  • 4.0 *** Infrastructure
  • 4.1 Access
  • 4.2 Electricity
  • 4.3 Communication
  • 4.4 Planning Permission
  • 5.0 *** Cultivation
  • 5.1 Stevia Strain
  • 5.2 Planting
  • 5.3 Seed/Transplants
  • 6.0 *** Fertilisation & Weed Control
  • 6.1 Fertilisation
  • 6.2 Weed control
  • 7.0 *** Economics of Production/Yield
  • 7.1 Economics of Production
  • 7.2 Yield
  • 8.0 *** Cultural Practices
  • 9.0 *** Harvesting
  • 9.1 Timing and Technique
 
When cultivating stevia first and foremost it is important to study its environment and climate. In this section we will cover climate, humidity and latitude.
Stevia is native to semi-humid, sub-tropical climates where temperatures typically range between -6°c to 43°c. Stevia requires 12-16 hours of sunlight per day and is sensitive to excessive heat and low temperature. Excessive heat may cause heat stress/dehydrate the plant and consequently cause leaf withering. While tolerant to mild frost, hard frost’s will kill the roots of the plant. In fact the plant will only tolerate temperatures up to -6°c. This lack of winter hardiness is important to note for cultivators in cooler climates. The ideal temperature ranges between 15°c to 30°c. Extensive cool periods are undesirable as the plant will go into a dormant state. Areas prone to excessively hot, cool or frost periods should therefore be avoided. Stevia is likely to do well in arid/semi-arid areas with predictable rainy seasons and enough access to fresh water for irrigation. Examples include, but are by no means limited to, the north part of Latin America such as the North East of Brazil, the Mexican East coast and the Chilean West Coast. Certain areas in North Africa such as Morocco also qualify along with various areas in the US.
High humidity and rainfall will promote leaf disease. It can be challenging and costly to find approved/registered pesticides that effectively prevent leaf disease in stevia as pesticide registration lags behind pesticide use. Therefore you should carefully select your cultivation area. Preferable locations host extensive dry seasons. Rainy seasons are preferred over sporadic ones to avoid leaf disease.
Stevia Rebaudiana is a short day plant. Stevia planted at latitudes close to the equator tend to flower. This is a problem as when the stevia plant start to flower the Steviol glycoside content usually decreases rapidly. Stevia tends to stay vegetative during summer when grown further from the equator. Stevia clones could be selected that resist flowering near the equator.
Water and irrigation are critical for successful stevia cultivation. In this section we will cover plant water requirements, access to water and irrigation.
It goes without saying that this is subject to many variables, but as a general rule of thumb stevia requires 1800mm per plant per annum.
The site has to have access to plenty of affordable fresh water all year round as stevia does not tolerate drought. Stevia does not tolerate excessively wet soil either. Therefore it is essential the site does not flood in the wet season yet has good and continues access to clean water in the dry season. 
Irrigation is crucial as stevia requires frequent, shallow irrigation. Generally, irrigation is required when the voice tips start drooping. Drip irrigation works best for stevia cultivation, especially for larger sites in arid areas as it preserves water. Another benefit to drip irrigiation is that stevia is susceptibility to leaf disease. Adequate water supply will avoid stress in the plants, which will result in less diseases and better biomass production. Access to plenty of fresh water, enough to cover during the dry season is key.
In terms of soil stevia is not too demanding, however various other factors must be carefully considered to ensure a successful crop. In this section we will cover soil, field design, levelness and firmness of the land along with the use of raised beds. 
The chemical and physical conditions of the soil are important. Stevia grows well on infertile, acid soils, but can also be cultivated on more neutral soils (pH 4.5 – 8). Stevia will not grow in saline soils.
Field design is important to avoid washing out the soil and to preserve water. Land should not be prone to floods or puddles. It should not get saturated during the rainy season. It has to be able to absorb the water and/or have reasonable drainage. Slight elevation will often prove beneficial. The land is preferable in a rectangular/square shape, or at least with ‘easy’ to manage borders.
For industrial scale cultivation relatively level areas are required along with a relatively firm underground to sustain various machinery including those required during plantation and harvesting. Generally fields should be ploughed and either diced and/or cultivated twice to prepare a fairly smooth, firm planting surface. Land should be prepped or relatively easy to prep for agricultural use. No or little trees and rocks etc.
Unless your soil is very sandy, raised beds are ideal for Stevia. This will prevent soil fungi as it will encourage proper draining.
This is absolutely essential. You need to import and export from the land, have stable sources of power to ensure stable irrigation and so on. In this section we will cover access, electricity, communication and planning permission. 
Reasonable access to the site is essential for import and export from the land including machinery.
A reliable electricity supply or the possibility the get a stable source of electricity at a reasonable expense is indispensable for plant propagation, irrigation and (depending on your refining process) drying.
Something taken for granted by many but not as not in parts of the world readily available: wired or mobile internet access. 
Beyond agriculture planning permission you also need to account for various building structures, such as a lab, nurseries, greenhouses, warehouses, accommodation along with possible a distillation/refinery site.
When it comes to cultivation there are various key aspects to consider. Here will we cover stevia variety, planting and seed/transplants. 
There are many stevia strains/species, roughly between 200-300. Criole, Eirete, Katupyry, Morita II and III are some of the better known ones. There is a lot of innovation going on in the Stevia strain market, primarily with the intention to increase the Reb A content of the plant. Reb A is generally the most sought after stevioside, due it having the best taste/least liquorice after taste. Some companies like Coca-Cola in collaboration with Cargill (Truvia), Pepsi-Co/PureVia and GLG lifetech have patented there stevia strain. We are making use of a proprietary/patented strain with excellent TSG levels. Don’t obsess about these values though, other factors such as resistance to disease, biomass, water demand of the plant along with all the variables associated with your site location and cultivation practises may be considerations that are just as important.
Generally in spring stevia plug plants are 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. However this may vary due to various factors. The figure generally ranges between 60.000 to 100.000 plants/ha. 
Transplants from cuttings are considered superior, yet the cost are prohibitive. Stevia is generally propagated from seed in plug trays placed in a greenhouse for a period of 7 to 8 weeks.
Fertilisation and weed control are important aspects. In this section we will cover both suggestions on fertilisation and weed control.
The plant appears to have low nutrient requirements, however a soil test should be conducted. Minimum fertilisation may be a necessity.
Repeated mechanical row-cultivating can be used to control weeds. The crop may also require hand hoeing and weeding. 
What to expect 
Green leaf yields range between 5-9 ton per/ha during an optimum harvest period. Stevia is commercially produced in temperate regions of the world where it can be grown as a perennial crop. Development or winter hardy varieties of stevia could enlarge its cultivation area. Stevia is currently even being grown in Canada, Southern England and France. 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 trans planting, harvesting, mechanisation or techniques in drying and threshing, and the registration of pest control products. 
An estimated 25,000 – 50.000 kg/ha/yr of green weight is dried down to between 5.000 and 9.000 kg/ha/yr of dry weight. The yield of stem and leaf is similar at approximately 3,000 kg/ha each. Leaf mass yield can however range between 5,000 kg/ha to 9,000 kg/ha. The conversion to stevioides, 95 % pure Reb A and other steviol glycosides will depend on the variety but for calculation purpose one can assume that every 1000 kg/ton of dried leaf will give you 40-50 kilos of pure Reb A and same amount of other steviol glycosides.
Stevia is an intensive horticultural crop. It requires much greater expenditures and care than ordinary field crops such as corn, beans, alfalfa, rice, or wheat. The application of extensive agronomy to stevia is usually a failure. Intensive crop mentality is required.
Stevia can be harvested up to 4 times per year. The actual amount of harvests are especially dependent on the climate but cultural practices will also play a role.
The stevia plant (in warmer climates) is harvested three to four times a year. Optimum yield (biomass), and stevioside quality and quantity are best just prior to flowering. Specialized harvesters are recommended to mechanize the harvesting process. There are various provides of such machinery, such as Oxbo.
 

The above guidelines give you an insight on some of things we focus on during stevia cultivation. Perhaps you are using this information for your own cultivation activities. Please do remember that these are guidelines only and that before venturing into stevia cultivation thorough research would be recommended. For additional information on the above please contact us.



 

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