The stevia plant is a perennial but the growing cycle varies greatly depending on the particular strain and location. Stevia is sensitive to frost and in China where most stevia is grown today, it is common to only have one or two harvests. The cultivation of stevia in China began in the 1970'. In 1985, Jining city of Shandong province became the world's largest stevia planting area in the world. Jining - the location of Aoxing Stevia, is renowned as the "town of the world's stevia".
Stevia cultivation in China amounted to about 4,450 hectares (ha) in 2005, increased up to 24,685 ha in 2010, but decreased to only 2,666 ha by end of 2013. By 2010, Chinese production exceeded global demand and the stevia farmer’s profit margins were slim, so the cultivation area already began to decrease in 2011. The reason that a shortfall is that the market has been working through reserves left from the 2010 and 2011 harvests. It is reported that growers haven’t benefited as much as expected from increased demand, yet some increase in cultivation area was there in 2014.
Basic package of practice followed in China
The PH value of the soil should be between 6.0 – 8.0. The land should have irrigation facility and soil should have ample drainage, as waterlogging is detrimental to Stevia crops.
Before land preparation, Paraquat 20EC is applied for killing the weeds. After three days of herbicide application, land preparation is started.
Then the land is cultivated with tractor and farm implements. The cultivation generally involves 4 operations.
1. Chisel plowing - for loosening and turning the soil
2. Disc Harrow - for breaking the clods
3. Rotovator application (optional) - for getting finer tilth
4. Tractor drawn land leveler - for leveling the field
In China, transplantation both on flat land and or raised beds is practiced. In flat beds, drip irrigation is generally adopted. Furrow irrigation is generally adopted in case of raised bed plantations.
The above pictures show two different transplantation methods. For the transplantation on ridge, the space between the ridges is recommended to be 30cm. Mulching film is not needed for the areas Where the temperature at night is higher than 20℃.
For making the raised beds, often a combined ridging fertilizing implement is used. After making the beds transplantation starts. The transplantation is often done with tractor drawn mechanized transplanters. Transplanters are not suitable for the plantation system which uses mulches with pre-made holes. In plantation systems with mulches, generally manual transplantation is practiced.
The effect of organic manure and chemical fert ilizer on growth and development of Stevia rebaudiana Bertoni had been studied in experimental plots in Qingdao Agricultural University. The results showed that organic manure cultivation promoted root activity in 40 days after transplanting compared with the chemical fertilizer cultivation, and the dry weight of the above-ground has exceeded chemical fert ilizer cultivation in 60 days after transplanting. The glycosides synthesis and accumulation main period was in the later growth stage, and organic manure improved the root activity and enhanced the photosynthesis rate in later growth stage, finally the biomass of stevia and the content of glycosides were also increased.
In China, Stivia is harvested after 120 days of transplantation. The harvesting is generally done with small machanized harvesters. After cutting the plants, they are allowed to remain in the field to dry, or in wet seasons, theey are often dried in poly tunnels. If the leaves are allowed to dry in the field, they are collected manually.
The leaves dry faster if they are seperated from the stem. The leaf stem seperation is generally done by small semi-automatic de-foliating machines. The dried leaves are baled in hydraulic balers and stored.