Stevia Farming in Polyhouse, Cultivation Practices

Introduction: Hello polyhouse farmers we are here with an excellent information of stevia farming in polyhouse and it’s cultivation practices. Stevia is a small perennial herb belonging to the Asteraceae family and its scientific name is Stevia rebaudiana. Some commonly referred names are honey leaf plant, sweet herb, sweet chrysanthemum, sweet leaf stevia, sugar leaf, etc. It has zero calories and no impact on blood glucose levels. It is native to the altitudes of Paraguay and Brazil in South America, and it has been used as a sweetener for hundreds of years. It is a subtropical plant that requires warm temperatures with minimal frost, adequate rainfall, and lots of sunshine. The Stevia plant genus includes over 100 species and it is cultivated throughout the world.

A step by step guide to stevia farming in polyhouse

Traditionally, Stevia was used to sweeten teas, and for its medicinal properties. Refined stevia products are obtainable for a more standardized sugar substitute, but with a little creativity, you can use dried leaves or extracts in many different recipes.

As increasing volumes of stevia are in demand by consumers, the stevia is also now developed in Vietnam, Brazil, India, Argentina, and Colombia among other countries. The genus Stevia plant contains about 154 species. Among these six species are mostly utilized that are Stevia eupatoria, Stevia ovata, Stevia plummerae, Stevia salicifollia, Stevia serrata, and Stevia rebaundiana. Stevia rebaundiana is the one with significant sweetening properties.

Stevia is being cultivated on a commercial scale in Japan, China, Thailand, Paraguay, and Brazil. Present, China is the leading exporter of stevia products. It is grown by natural, conventional plant breeding methods that are cross-pollination and other non-genetically modified processes. When grown in the right places, stevia pant can be a hardy, sustainable crop for small, independent farming communities. Depending on the region, it can be harvested several times per year and requires little farm acreage. The stevia plant is grown best in environments with long days of sunshine and is a perennial plant.

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The stevia is the first choice of the sugar-free industry and the sweetener of stevia is widely used in the world. The crop is planted for five years and after the fifth year, the marginal return starts to decline so it is best to uproot crop and replant it. Stevia farming in India is having a bright future.

Requirements for stevia farming in polyhouse

Low-cost polyhouses can be used to protect crops from excessive rainfall and can give a sheltered environment for the production of better quality crops over the rainy season cropping period. Precise irrigation and fertilization are probable in the polyhouse structure. Export-oriented production is most possible under these polyhouse structures.

The size of the polyhouse structure can differ from small shacks to big-size buildings as per the need. The stevia plants inside the polyhouse farming are hale and hearty. Fertilizer application is easier and is controlled automatically with the help of a drip irrigation system. Polyhouse farming gives the right environmental facilities to plants in any season. Cultivating stevia under polyhouse conditions and providing artificial environment congenial for its growth and quality blooms is considered as another option to generate the crop throughout the year. For this, the entire parameters essential for flower production are provided under controlled environmental conditions. The temperature, humidity, and aeration, etc are modified according to crop needs.

Polyhouse also increases yield for about 5 to 10 times. Polyhouse farming provides an optimum environmental medium for better crop growth to gain maximum yield and high-quality products.

Plants grow faster inside the polyhouse structure because the temperature remains a little higher inside the poly-house, even when it is cooler outside. Management of insect pests, diseases and weeds are easier under these polyhouse structures.  These polyhouse structures are ideally suited for small farmers and unemployed youth from rural areas. Any type of land can be used for the erection of polyhouse structures.

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Site selection and soil preparation for Stevia farming in polyhouse

Site selection is a very important factor in Stevia polyhouse farming. A good site selection can make all the difference in the functional and environmental operations of a polyhouse structure. The soil pH level for the stevia farming in polyhouse is 4 to 5. The availability of a continuous source of quality water will be very important.

Stevia plant prefers a sandy loam or loam incorporated with organic matter is the best way to improve heavy, high clay soils. Stevia requires good drainage; any soils that retain the moisture for a long period of time are unsuitable for Stevia cultivation that should be religiously avoided. Similarly, black cotton soils with very heavy clay content should be avoided.  The Stevia plant prefers a lightly textured and well-drained soil to which organic matter has been added.

Rich compost made with leaves, grass, hay, kitchen waste, manure, and other organic residues will develop soil structure and supply nutrients. Finished compost can be tilled, disked, or spaded into the soil before planting or used as mulch later on. Growing a ‘green manure’ crop the previous year such as oat, rye or legume will also develop heavy soils. Stevia occurs naturally on soils of pH level 4 to 5 but thrives with soil pH level as high as 7.5. However, Stevia does not tolerate saline soils.

Land preparation for Stevia farming in polyhouse

The land sites are plowed twice to arrange a  fairly smooth and firm-planting surface.  Approximately 50 MT of FYM/ha has to be applied as a basal dressing during the last plowing to incorporate the manure with the soil. With good drainage and irrigation channels, the field needs to be divided into plots of convenient size for effective management.

Growing conditions for stevia in polyhouse

Stevia has been able to provide a very important role in biodiversity because it requires little land and allows farmers to diversify their crops. Unlike commodity crops, stevia is normally grown on smaller plots of land and provides supplemental income to the more commonplace “cash” crops.

In part, because stevia is intensely sweet and is an extract, it normally requires only a fifth of the land and much less water to give the same amount of sweetness as other mainstream sweeteners. When growing conditions are most ideal, farmers normally harvest stevia multiple times per year.

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Stevia plant propagation in polyhouse

Stevia is generally propagated by stem cuttings, which root easily. Sweetness in plant leaves varies with varieties. Therefore, cutting must be obtained from a source, which is high inside and low in associated bitterness during propagation and mother plant selection of Stevia. Seedlings can be ready for transplanting after two months of nursery raising.

Stevia plants can be propagated mainly from cuttings or seeds or by tissue culture. As the seed germination is poor and seedlings are very slow to establish, it is generally propagated clonally through cuttings. For vegetative propagation, stem cuttings of 15 cm length taken from leaf axils of the current year’s growth have been given good results. Treatment with Paclobutrazol @ 100ppm has been creating to induce the root initiation in a short time and IBA@500 ppm is also found to be effective.

Stevia planting process in polyhouse

In polyhouse, Stevia plant seedlings are planted in the middle of a raised bed having 15 cm height. Forming raised beds is the most economical way to grow Stevia plant. The distance between two rows must be between 40 and 60 cm and that between each plant must be 20 and 25 cm. The pots must be totally covered by soil during the planting of stevia seedlings on the cultivation field. This would give a plant population between 70,000  and  100,000 per hectare.  Depending on climatic conditions, the Stevia plant is cultivable throughout the year except for times when it is extremely hot or cold.  The planting time of  Stevia must be done at the commencement of the main rainy season.  It is possible to plant at any time in areas where irrigation is available.

Fertilizer dose for Stevia farming in polyhouse

Fertilizer requirements are moderate for Stevia farming, partially due to its adaptation to poor quality soils. Nutrient usage of Stevia plant might be 105 Kg N, 23 Kg P, 80 kg K per hectare based upon nutrient removal through harvesting, maximum rates of NPK 40-20-30 are suggested for India. A higher rate with split dressing, mainly, for nitrogen is also suggested. 

Irrigation requirement for Stevia farming in polyhouse 

Irrigation is normally assumed to avoid any water stress on plants unless the growing area has reliable rainfall throughout most of the year.

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Drip irrigation is the best technique for watering the Polyhouse Stevia plants owing to the small root system. It should be ensured that the water is dispersed at the root area only and that it does not fall on the leaves. Falling on leaves may lead to infection, disease spread and even scorching. Water is forced out through the nozzles under high pressure through the micro-sprinklers. These sprinklers are arranged at a height of one foot above ground level to ensure that water is dispersed at the basal part of the plants.

Normally, the Stevia plant requires frequent, shallow irrigation. Under the conditions of limited rainfall, the application of supplementary irrigation is necessary at least once in a week when the tip leaves start to droop. Stevia plant requires an ample supply of good water all year round.  The plant cannot tolerate drought because of this frequent irrigation is necessary. Micro sprinklers are the best method of irrigation that would not supply the required amount of water at the right time.  So through micro-sprinklers, the water can be sprinkled once in a day in wet seasons and 2 to 4 times in a day in dry seasons depending upon the heat and relative humidity in the air. Watering frequency must be scheduled so that the plants do no wilt for want of water.

Pest and diseases in Stevia farming

Stevia is not known to have serious insect pest problems and often reported as exhibiting insect-repellent qualities in field conditions. The documented account of diseases is less in number so seemingly insignificant. Even though, some pest and disease problems occurring in the Stevia plant are given below.

Weed – Stevia seedlings are very susceptible to weed competition until well established.  Black plastic mulch and high-density planting (up to 200,000/ha) have also shown to be effective for weed control. Alternative planting process and hand weeding will control the infestation of weed in the field.

Stevia crop requires hand hoeing and weeding. After every 2 months, there should be weeding and regular weeding must be done in stevia cultivation.

Insects – Insects do not appear to be a problem and Stevia has shown clear aphid resistance the sweet taste is a possible deterrent to insects. Slugs have reportedly attacked new tillers after winter dormancy. In polyhouse conditions, aphids, thrips, and whiteflies can become a serious problem with Stevia.

Disease – Disease does not appear to be the main problem either, although there are reports claiming to record the first known incidence of Sclerotinia, leaf-  spot Septoria and black-spot Alternaria infections.

Stevia harvesting in polyhouse

The first harvest of the Stevia can be in four months after planting and subsequent harvest once every 3 months. Some times 40 to 60 days after harvest are sufficient for subsequent harvests and short days induce flowering. Optimum yield and stevioside quality and quantity are obtained just at the time of flower bud initiation. As days to harvest vary from place to place, it is good to harvest plants at the time of 50% flower bud initiation. The easiest harvesting method is to cut the branches  5 cm above the ground level with pruning shears before stripping the leaves. The tips of the stems can be clipped off and added to harvest yield, as they have as much stevioside as do the leaves.  On average three harvests can be obtained per year. It is better to cut the Stevia plants leaving about 10  cm stem portion from the ground. This will help new flushes to emerge, which can be harvested as the next crop. For domestic use, leaves can be used fresh for tea or may be combined with mint leaves.

Drying

Drying of the woody stems plus the soft green leaf material is completed immediately after crop harvesting, utilizing a drying wagon or a kiln. Depending on weather conditions and density of loading, it normally takes 24 to 48 hours to dry Stevia at 40°C to 50°C.

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