One of the most promising sources of natural low-calorie sweets are introduced from South America perennial grassy plant Stevia rebaudiana Bertoni, in leaves which contains at least eight different dyterpenovyh glycosides with exceptionally sweet taste.

In our country work on the biological and agronomic features of this plant for its introduction started in 1986 and are held in different soil and climatic zones.

One of the main problems in the introduction of stevia in Ukraine are growing it in the field on a one-year cycle and explore important issues such as the timing of planting, the area of ​​the power plant predecessors stevia, soil and their cultivation, fertilizer, care of plants, harvesting and other .

 

 

Due to the fact that part of the commodity for which it is grown, there are leaves all agricultural practices should be directed

for optimum leaf surface at which leaves would have the best opportunity for photosynthesis, and hence for the biosynthesis dyterpenovyh glycosides.

Predecessors

Due to the fact that stevia feverish culture, its predecessors should be vuzkoryadnoho plants or continuous mode sowing; it can be grass, grain (preferably green fodder), legumes.

Soils and their cultivation

To grow stevia field is treated in the same way as for later growing cultivated crops. But soil preparation should be done carefully, because the root system of stevia landing is not very well developed; In addition, stevia in the first period of growth is growing slowly.

Stevia is best for soils with light texture, slightly acidic, with a high level of groundwater. On heavy soils, rich in organic matter, disease can develop the root system.

In the spring, in the field, which will be planted stevia, spend mulching, and then - the first culturing a depth of 12-14 cm. The second culturing spend a few days before transplanting. In this period especially need to pay attention to the quality of the field: the lack of weeds and soil rozpushenist guarantee quality planting plants.

Seedlings planted in open ground when the threat of frost passes and the average air temperature is 10 0C.

Planting of Stevia. Density standing

The manual planting of seedlings Stevia cut deep furrows 15 cm to provide vertical placement of the root system. In the furrow before planting pour water absorption and soil after the plants are planted, deepening of 1-2 cm above the root collar, or the first pair of leaves. If the plants have grown, the landing can be made a little deeper. After planting, the plants should be well watered from above to the ground and sat near the roots were not formed cavity, as in this case, the seedlings take root poorly.

When planting in open ground valuable material, to increase the multiplication factor can be used slightly modified planting seedlings obtained by in vitro culture so as to bury into the soil at least 3-4 internodes horizontal. With this method of planting rhizomes formed stacked that after winter storage of the divide in the transverse direction to the stem and planted in a prepared mixture.

The most valuable part is the leaves of stevia harvest, which accumulate sweet glycosides. Therefore, the cultivation of stevia is necessary to provide for optimal growing area of ​​leaf area.

From the stand density of plants depends on their rate of growth and development, plant morphology, intensity of light, and hence the accumulation of biomass and its quality.

One of the main issues Stevia cultivation technology is to optimize the feeding area. The optimal stand density of plants in the field is one of the important conditions for growing high yields. This problem has found an echo in many foreign scientists. So, Sakaguchi, studying stevia planting density in the range from 80 to 400 thousand / ha, showed that the most effective placement of 1 hectare 100,000 plants. in Paraguay, the best option was 45 thousand / ha, and in California (USA) - less than 200 thousand / hectare. But these authors recommendations related to research on the cultivation of stevia as a multi-culture.

When studied stevia planting density in western steppes of Ukraine noted that in the initial phases of development of plants biometric measurements found no difference in plant height, number of internodes and number of stems. But after a while this difference begins to appear. Thus, when the density of planting 120 thousand / ha plants were 10-12% lower than the density of 80 thousand / ha, and the number of internodes - slightly larger, thus ensuring better oblystyanist plants. options with different density planting different plants for harvest wet and dry mass of leaves. In embodiments with lower density mass per plant increased: at 80 thousand / ha it was 168 g and 60 g, respectively; at 100 thousand / ha - 160 g and 55 g; at 120 thousand / ha - 149 g and 50 g also noted the difference in percentage of dry weight of leaves and stems. In larger stand density, it was higher for leaves (54-58%), with smaller - for stems (46-48%).

In laboratory experiments, technology of cultivation of stevia planting seedlings vyvchly density depending on the distance between plants in a row schemes: 45h20 cm, 45h30 cm, 45h40sm.

Studies have shown that when planting dilution (increase in the area of ​​power plants), the average weight per plant increases and harvest the entire aboveground mass and leaves - reduced.

As a result of studies found that when growing stevia under steppes of Ukraine advisable to plant stevia scheme 45h20 cm (row spacing of 45 cm. The distance between plants in a row 20 cm). This scheme provides stand density planting 111 thousand. Pieces of plants per hectare and allows you to more fully use the capabilities of soil fertility considering the biological potential of stevia. With such a density obtained maximum yield total weight of the plants, raw leaves, total dry weight and speed dry leaves. Increased stand density by reducing the row spacing of 60 to 45 cm a positive effect on increasing yield of green mass per unit area. The harvest of dry leaves with an average of 2.4 t / ha, which is 15-20% higher compared with the harvest, obtained at 60 cm between rows.

By increasing the distance between plants in rows 20 to 30 centimeters of dry leaf yield decreased by 16.7%, while increasing the distance of 40 cm - 37.5%. Due to the fact that the commodity is part of the stevia leaf, the proportion of the total ground mass is important in the total harvest. In experiments conducted with increasing distance between plants out of leaves, wet and dry increases. Many researchers in other cultures have shown that increasing the area of ​​individual power plants form more leaves, increasing the size of leaves. According to other researchers in adapting to thickening ratio between the biomass of leaves and stems remain unchanged. Such factors as out of the total dry weight of raw, dry leaves and out of the total wet weight in experiments in ways not much different. Most power in the area tenuous landing (55-74 thousand. Pieces of plants per hectare), undoubtedly provides the best conditions for the growth and development of each individual plant. But the best is such a stand density of plants at which maximize yield achieved basic production per unit area and the greatest productivity of a plant.

As for the timing of planting stevia should be noted that earlier, the May planting seedlings in open ground without allowing customers to obtain higher yields. This is longer during the growing season in the field, as well as favorable conditions engraftment seedlings.

Early planting periods (23-25 ​​May) in the soil is kept enough moisture that promotes better healing seedlings. As the biometric measurements, the plants planted later (June 8-10), although not very behind in comparison with May plantings, but the number of internodes, stems and oblystyanosti lag was significant.

Oblysyanist plants planted earlier, more than twice exceeded oblysyanist plants planted in a specific week of June. May timing of planting the crop in terms of June leaves far exceeded. Therefore, in the absence of the threat of frost stevia better planted in open ground no later than May 23-25.

For better healing seedlings commonly used paper tape (Paperpot) and peat pots. Stevia Laboratory ITSB technology of growing seedlings in paper tape for mechanized planting stevia. The use of paper cassettes with cells 5x5 cm and 5,5h6,5 cm enables rooting green cuttings and doroschuvaty plants obtained by in vitro. When growing seedlings of stevia in paper cassette is not inhibited root development and the transplant in an open ground is not damaged. Most root. The best substrates for growing seedlings in paper cassettes are: perlite / sand - 3: 1. and perlite / sand 3: 1 + soil mixture.

For mechanized planting stevia in paper cassettes can be used tobacco transplanter ski-6A roses or vegetable planting machines, rebuilding accordingly.

Seedlings planted in a field in peat pots in the first growing season is developing better than paper cassettes, and better than the one that was planted directly into the ground. Within a month it ahead of other indicators for seedling height and oblystyanosti. This is due to the fact that these plants are not travmuvalas root system was favorable nutrient and water regimes.

But in poor wetting peat pots to further restrict root development, resulting in suppressed growth and development of plants. In addition, plants in peat pots intensely affected by fungal diseases, which causes crop shortfall.

The lowest yield of green mass was obtained in those embodiments where direct landing of seedlings was performed in soil. This is because the transplant seedlings into the soil much poshkodzhuvayetsya root system, plants take root poorly and slowing growth of plants in the early growing season.

The highest yield obtained in early, the May timing of planting seedlings, planted in paper tape with a width of 45 cm between rows. In this method of planting seedlings in 30-33% yield was higher than the direct planting into the soil and 15-20% higher than planted in peat pots.

Caring for plants.

After planting the seedling to its healing systematically need watering and loosening the soil. Once, when the seedlings take root, watering should be done when necessary because excessive irrigation during this period did not contribute to the normal development of the root system. During the intensive growth of stevia spend watering so that water penetrated to a depth of 30-50 cm. Due to the fact that stevia does not tolerate drought, watering should be done more often.

When loosening plants Care should be conducted not close enough to the plant, because the latter are very fragile and easily broken, but the root system, placed superficially on the surface of the soil by careless cultivation may be corrupted. For normal growth and development of stevia soil should be loosened. For optimum air regime during the growing season should be done 3-4 and loosening to combat weeds.

Fertilizers stevia

When growing seedlings Stevia conducted experiments to determine the optimal doses of fertilizers made in the substrate, which would provide good healing plants and high quality seedlings. The results showed that when growing seedlings on a substrate with perlite, sand density of 225 units per 1 m2 plant is making the most optimal 0.4 m2 substrate, for growing seedlings of plants obtained from tissue culture: N - 1-2h, P2O5 - 2g, K2O - 2g; When growing seedlings from cuttings: N - 2-3 g, P2O5 - 2-3 g, K2O - 2-3 g in the form of simple fertilizers.

To study the effects of key battery performance stevia obtained from seedlings in vitro, experiments conducted vegetation, which studied the effect of nitrogen, phosphorus and potassium, as well as double and triple combinations of these batteries.

The optimal dose of fertilizer per bushel was: nitrogen (N) - 2 g of phosphorus (P2O5) - 2 g of potassium (K2O) - 2 g; in variants with the introduction of double doses - the amount of main nutrients doubled. Fertilizers made in the form of ammonium nitrate, superphosphate granular simple, 40% potassium salt. In each jar planted one plant derived from culture in vitro.

Conducted in ITSB studies have shown that when making a vessel of only phosphorus in the second half of the growing season and especially before the gathering, the plants did not have other batteries, especially nitrogen. This led to it. What stevia leaves become pale yellowish green and rolled upper leaves and withered, plants were taken out mainly by increasing internodes. The increase in mass of stevia plants in this version compared to the control without fertilizing an average of three years was 94.2 grams dry weight of leaves - 12,7 g tlky made with potash and phosphate and potash fertilizers stevia leaves on plants and zhovtily skruchuvalysya, especially before compiling it. Increasing crop plants and dried leaves these options was respectively: 49.7 g, 4.0 g, 90.5 g, 11.8 g version-controlled plants in appearance were normally developed, with no signs of depression, but much smaller sizes.

Making paired combinations - nitrogen phosphorus or nitrogen with potassium plants were well developed, green and kept follows until the harvest. Increase in plant mass were respectively 151.4 grams and 140.5 grams of dried leaves and weight - 20.8 and 19.1 g

Adding three batteries in one dose was the most effective; crop plants by an average of 3 years increased by 213.1 g of dry leaf weight - 28, 9 g

When making double dose of fertilizer (2NPK) observed a significant inhibition of Stevia plants, especially after feeding nitrogen. The edges of the upper leaf fertilizer compared to single dose adversely affected the performance of stevia. In addition, vsnesennya double the rate suppressed the development of plant roots.

Determination of dyterpenovyh glycosides found that of nitrogen had no effect on their content in the leaves of stevia. Making phosphorus observed downward trend in the number of stevioside in the leaves of stevia, and making increased potassium content glycosides. Especially stevioside. Paired fertilizer combination compared with a control option helped increase the number of glycosides in the leaves, especially in making nitrogen and phosphorus; content amount glycosides (stevioside and rebaudozydu) is increased compared with control at 2.03%.

Adding three batteries (2 g of active ingredient per vessel) increased the percentage glycosides in leaves at 1.51%, mainly due rebaudyozydu A, the amount of which was 3.23%.

In the double dose of fertilizer (2NPK) observed a significant inhibition of plants and reduction of glycosides compared to the control at 2.06%, as compared with one dose - almost doubled.

Thus, stevia ensure the highest performance of nitrogen, phosphorus and potassium at a dose of 2 grams of active ingredient per jar. The mass of dry leaves per plant was 45.4 g, and dyterpenovyh glycosides content - 7.51%.

In order to determine optimal doses of fertilizers when growing stevia in the forest-steppe zone of Ukraine also conducted field experiments. In measurements conducted during the growing season of plants that showed that fertilizer positively affect plant height in the first growing season. Already during the mass difference in height budding of plants in ways hardly observed. But all variants noted earlier appearance on the plants shoots of the first order and a great intensity of their growth.

Application of fertilizers affected the harvest of stevia and its structure. Making fertilizer doses: N60P60K60, N120P120K120 i N60P60KK120 observed downward trend in the percentage of stevia leaf in the crop. Adding a dose of fertilizer increased yield N60P60K60 stevia plants at 71.4 kg / ha and a lot of leaves - 38.6 c / ha compared to the control, and a lot of dry leaves - 8.3 kg / ha.

According Ksendzov LI, in making N120P120K120 stevia harvest decreased compared to the dose N60P60K60; Plant growth and dry mass of leaves compared with control of 45.5 and 5.5 kg / ha.

Increasing the dose of one of the batteries up to 120 kg / ha crop of stevia reduced compared with a dose of fertilizer N60P60K60, especially with increasing doses of potassium.

When harvesting in dry stevia leaves was determined dyterpenovi glycosides (glycosides determination carried Jaworski TK and Seoul TA). It was found that fertilization affected the composition dyterpenovyh glycosides in the leaves. On average, two years making N60P60K60 glycosides content increased to 0.98% compared with the variant without fertilizers. Increasing the dose of fertilizer to N120P120K120 not glycosides content increased compared to the previous dose, but the mass of absolutely dry leaves increased.

With increasing doses up to 120 kg / ha of a battery marked trend of increasing glycosides content in leaves with increasing doses of phosphorus and significant decrease, taking increasing doses of potassium.

The highest premium (0.73 kg / ha) glycosides collection per hectare obtained in making fertilizer dose N60P60K60.

Thus, the optimum dose of fertilization in the area of ​​stevia in steppes of Ukraine on gray forest soils is N60P60R60, which provides increased crop plants to 71.4 kg / ha of dry leaf weight of 8.3 kg / ha and content dyterpenovyh glycosides in stevia leaves - on 0,98% when the crop plants in the control version (without fertilizers) 189.1 kg / ha of dry leaf weight - 27.7 kg / ha and the amount glycosides - 45.53%.