Efficiency of microfertilizer application to medicinal plants grown under conditions of southern forest-steppe of Western Siberia

. The article presents the results of studies on the effectiveness of mineral fertilizers (zinc and copper) in the cultivation of perennial medicinal crops ( Achillea millefolium L., Tanacetum vulgare L., Echinacea purpurea L.) on meadow-chernozem soil in the southern forest-steppe of Western Siberia. It was found that the most effective for Achillea millefolium was the application of copper fertilizers in the soil at a dose of Cu 9.7 , providing an increase in yield by 43.2 % relative to background; for Tanacetum vulgare – zinc fertilizers at a dose of Zn 60 (+42.9 % relative to background) and for Echinacea purpurea copper fertilizers at a dose of Cu 9.4 (+60.3 % relative to background).


Introduction
Researches of scientists [1][2] have established that chemicalization means supply insignificant amount of microelements to soils.In this regard, there is a deficit and negative balance of trace elements in soils and plants, which in turn leads to a decrease in crop yields and deterioration in the quality of crop production [3].
In many regions of our country, low soil supply of mobile forms of trace elements (copper, zinc, etc.) is noted [4][5].Agrochemical monitoring of soil fertility in the Omsk region showed that 98.9% of the surveyed areas are characterized by low content of mobile zinc, as well as low (47.1%) and average (50.0%)levels of mobile copper in chernozem soils [4,[6][7][8][9][10].The content of trace elements in soils insufficient for plant growth and development leads to significant losses in crop production, reducing the yield and quality of agricultural crops, as well as to the development of endemic diseases in animals and humans [11][12][13][14][15][16].In this regard, biofortification of agricultural crops [17][18][19], including medicinal crops, with certain essential trace elements, such as zinc and copper, has gained importance in recent years.
The introduction of essential trace elements into the soil activates enzymatic processes in medicinal plants, thereby increasing the biosynthesis and accumulation of biologically active substances in them [20].In medicinal plants, trace elements are in an accessible form, which increases their assimilation, as well as the connection of trace elements with biologically active substances contributes to the enhancement of pharmacological effects [21].Consequently, the study of the effectiveness of microfertilizers of perennial medicinal plants is an urgent problem and is important in the development of medicinal plant breeding in the Russian Federation [6].
The relevance of the ongoing research is also associated with the implementation of the project "Revival of Medicinal Plant Industry in the Russian Federation" within the framework of the National Technological Initiative (NTI) in recent years.According to the road map "Healthnet" it is planned to create by 2035 about 300 thousand scientific and educational agrotechnoparks and farms engaged in the cultivation, primary processing and storage of medicinal raw materials [22][23].In this regard, the study of introduction, agrotechnics, physiology and biochemistry of medicinal plants is of particular relevance [24][25].
The aim of the research was to study the effectiveness of microfertilizers (zinc and copper) in the cultivation of perennial medicinal plants (Achillea millefolium L., Tanacetum vulgare L., Echinacea purpurea L.) in the conditions of the southern forest-steppe of Western Siberia.[field experiment № 3]) to study the effectiveness of different doses of zinc and copper fertilizers were conducted during 2012-2018 on the experimental field of Omsk GAU on meadow-chernozem soil.In the year of laying experiments No. 1-2 (2012) there was a very low content of nitrate nitrogen, the provision of mobile phosphorus was average, exchangeable potassium -high.In 2016 (experiment No. 3) low nitrate nitrogen content, high mobile phosphorus and very high exchangeable potassium were observed.The content of mobile zinc before the establishment of field experiments was 0.65-1.1 mg/kg, copper -0.08-0.10mg/kg, which characterizes the low provision of soils with these trace elements [6].

Materials and methods
Experiments with Achillea millefolium and Tanacetum vulgare were conducted during 2012-2015, with Echinacea purpurea -2016-2018.The precursor was pure fallow.
Experiment schemes included variants with zinc and copper fertilizers applied on macroelement background (N 135 P 45 K 45 and N 125 ).The schemes of experiments are presented further in the text in the figures.
The conducted experiments are single-factor.In experiments No. 1-2, the variants were placed systematically, sequentially in one tier.In experiment No. 3, the variants were placed systematically in several tiers.The counting area of microdelsicles was 10 m 2 , the repetition was fourfold [26].
Mineral fertilizers were applied once in the year of planting medicinal plants in the form of ammonium nitrate, simple superphosphate, potassium chloride, zinc and copper acetate.
The field experiment was planted according to generally accepted methods [27][28] by seedling method in the middle of May.Care of medicinal plants included the application of mineral fertilizers, weeding, and loosening of inter-rows.Harvesting of medicinal crops was carried out manually, in August -September.
Meteorological conditions of vegetation periods in the years of research differed in temperature and moisture conditions, but in general were typical for the southern foreststeppe of Western Siberia.

Results and Discussion
The influence of trace elements on the processes of growth and development of medicinal plants during vegetation is reflected in the change in the yield of medicinal raw materials [6].
In the course of research, it was found that the yield of medicinal plants depended on the year of life of plants, meteorological conditions, applied trace element and fertilizer doses [6].
On average for the years of research (2012-2015), the highest yield of Achillea millefolium was observed when copper fertilizer was applied to the soil at a dose of Cu 9.7 and amounted to 13.4 t/ha (increment to background 4.0 t/ha) (Figure 1).The similar tendency was maintained when characterizing the total yield for the years of research.Payback of 1 kg of copper fertilizers by yield in the experiment variant Cu 9.7 was 1.67 t.

Fig. 1. Effect of microfertilizers on the formation of dry matter yield of total biomass of Achillea millefolium.
To a lesser extent, zinc fertilizers contributed to the increase in the yield of yarrow.The highest yield was observed when zinc fertilizers were applied on a nitrogen-phosphoruspotassium background at a dose of Zn 60 and amounted to 12.4 t/ha (increment to the background 3.0 t/ha) (Figure 1).Payback of 1 kg of active ingredient of zinc fertilizers by yield in the Zn 60 variant was 0.20 t.
In the field experiment with Tanacetum vulgare, the highest yield was observed when zinc fertilizers were applied to the soil at a dose of Zn 60 (Figure 2).
On average for the 2012-2015 research years, when applying the optimal dose of zinc fertilizers (60 kg a.d./ha), the yield increased by 6 t/ha or 42.3% compared to the background.Payback of 1 kg of zinc fertilizers within the optimal dose was 0.41 t.Copper fertilizers to a lesser extent contributed to the increase in the yield of medicinal raw material of Tanacetum vulgare.The maximum yield was observed when copper fertilizers were applied at a dose of Cu 7.2 (17.8 t/ha).At the same time, the payback from the application of copper fertilizers was higher compared to zinc fertilizers and was 2.02 t/ha.The growth and development of Echinacea purpurea was more influenced by copper fertilizers in our studies.The highest yield was observed when copper was applied at a dose of Cu 9.4 (13.2 t/ha).Each kg of copper fertilizer within 9.4 kg a.d./ha provided a payback of 1.59 t/ha.Zinc fertilizers increased the yield up to the dose of Zn 21.4 , above 21.4 kg a.d./ha the yield of Echinacea purpurea decreased to the level of control and background (Figure 3).Since not only Echinacea purpurea herb but also inflorescences and rhizomes are used in the pharmaceutical industry, the effect of microfertilizers on the yield of Echinacea purpurea inflorescences and rhizomes was revealed (Figure 4) [6,23].The highest yield of rhizomes and inflorescences of Echinacea purpurea was observed when copper fertilizer was applied at a dose of 9.4 kg a.d./ha and amounted to 13.1 and 5.0 t/ha, respectively (Figure 4).

Conclusion
The conducted long-term field studies allowed us to establish that the introduction of microfertilizers into the soil during cultivation of perennial medicinal plants in conditions of low availability of mobile forms of zinc and copper is effective.Microelements contributed to the increase in the yield of medicinal plants compared to the control and background.The highest yield in the experiments with Achillea millefolium and Echinacea purpurea was provided by copper fertilizers in doses Cu 9.4-9.7 (increase of 4.0-5.0t/ha); in the experiment with Tanacetum vulgare -zinc fertilizers in dose Zn 60 (increase of 6.0 t/ha).
Thus, the optimal doses of zinc and copper fertilizers for Achillea millefolium (Zn 60 and Cu 9.These doses can be recommended for cultivation of perennial medicinal crops of the family Asteraceae in the conditions of the southern forest-steppe of Western Siberia in order to increase their productivity.

Fig. 2 .
Fig. 2. Effect of microfertilizers on the formation of dry matter yield of total biomass of Tanacetum vulgare.

Fig. 3 .
Fig. 3. Effect of microfertilizers on the formation of yield of dry matter dry matter total biomass of Echinacea purpurea.