Effectiveness of foliar fertilizing spring oilseed rape in the forest-steppe conditions of central black earth economic region of Russia

. Trace elements are involved in almost all processes of plant life, despite the fact that they need very small amounts. The lack of trace elements in the soil does not lead to the death of plants, but is the cause of a decrease in the rate of their development. In the end, the plants do not realize their capabilities and give a low and low-quality crop. To solve this problem quickly, you can use foliar fertilizing with microfertilizers. The purpose of this study was to assess the impact of foliar fertilizing at different times with new types of complex microfertilizers on the productivity of spring rapeseed and the quality of its oilseeds.The experiments were carried out in the Lipetsk Region in Russia in 2019 and 2020 on Rif spring oilseed rape variety. Three types of fertilization during oilseed rape vegetative development were studied: a rosette stage, a bud-formation stage, and overlapping rosette + budding stage. The following agrochemical preparations were studied: Microel (0.2 L/ha), Life Force (0.4 L/ha), Boroplus (0.75 L/ha), Plantafol 20:20:20 (1 kg/ha), Plantafol 5: 15:45 (1 kg/ha) and Lignohumate (0.15 L/ha). The research results showed that processing foliar fertilization in the rosette stage with further feeding in the bud-formation phase were most effective. Because of the provision with microelements, vegetative plants were able to synthesize a full complex of enzymes. Plantafol 20:20:20 and Plantafol 5:15:45 micronutrient fertilizers provided the maximum increase in the rapeseed yield with double-spray processing, yielding 2.05 and 1.94 t/ha, respectively, and exceeding the control crops by 0.64 and 0.53 t/ha, respectively.


Introduction
Oilseeds are the most valuable agricultural crops in the world trade [11].Expansion of the range, of oilseeds grown types which allows for providing the population with a variety of very useful vegetable oils of local production [1][2].
Oilseed rape (canola) is an indispensable crop that is used in many different fields, including the edible oil production.This crop is one of the most popular oilseeds in Europe [14].
Today, rapeseed is the third leading oil crop in the world.Rapeseed oil has an increased biological value in terms of taste and nutritional qualities.The composition of the oil includes a large number of unsaturated fatty acids (oleic, linoleic, linolenic), which are essential in human nutrition [3;7;9].
To obtain high stable yields of this crop, it is important to consider the application of mineral elements in its cultivation technology in addition to varietal characteristics.The combination of mineral fertilizers and the optimal level of their doses for spring oilseed rape depends largely on the soil and climatic conditions of the cultivation region.At the same time, a lack or excess of fertilizers can negatively affect both the crop yield and quality.To increase the productivity potential of spring oilseed rape, it is necessary to optimize its nutrition in terms of macronutrients, and to balance it in terms of microelements (boron, copper, zinc, iron, manganese, etc.) since they influence positively the vegetative, phenological and germination components of the crop yield [4-5;10-11;13].
Nowadays, foliar feeding is actively used in cropping systems particular under adverse climatic conditions or severe minerals deficiency [6;8;12].Foliar feeding contributes to increased oil content in the seeds, improve oil quality and increase the crop yield of oilseeds [8;12;15-16].
The purpose of this study was to assess the impact of foliar fertilizing at different times with new types of complex microfertilizers on the productivity of spring rapeseed and the quality of its oilseeds in the conditions of the Central Black Earth zone of Russia.The effectiveness of foliar fertilizing with microfertilizers was evaluated by such indicators as an increase in the yield of spring rapeseed, an increase in the quality of oilseeds, an increase in the gross oil harvest per hectare and a reduction in the cost of finished products [9;17].

Materials and methods
The influence of micronutrient fertilizers in the form of foliar feeding on spring oilseed rape yield was studied in the experimental field of the Yelets State I.A. Bunin University in Russia, in 2019-2020.The soil of the experimental field is leached chernozem.The humus content varies in the range of 5.70-5.80%, the total nitrogen content is 0.285-0.292%,with 196.2-198.3mg/kg of phosphorus, and 114.7-115.0mg/kg of potassium.
Crop production practice for spring oilseed rape was used according to the recommendations generally accepted for the forest-steppe zone of the Central Federal District.The rapeseed predecessor was winter wheat.Rape was sown in the 3rd decade of April, with a seeding rate of 2.5 million seeds/ha.By the years of research from the 3rd decade of April to the 1st decade of May weather conditions were characterized by an increased temperature regime and high moisture reserves in the soil, which had a favorable effect on complete germination.In general, climatic conditions developed positively for the oilseed rape development, with the hydrothermal index (HTI) being 0.98 in 2019 and 1.28 in 2020.
The area of the trial plots was 20 m2; the area of the registration plots was 15 m2.A sheaf analysis of 21 samples in 4 dimensions was performed.In autumn, before the main tillage, Azophoska (nitrogen-phosphorus-potassium fertilizer) was applied (N:16P:16K:16), and in spring, the plots were fertilized with ammonium nitrate (N20).Oilseed rape crops were treated against cruciferous flea beetles with Alterr KE (Zemlyako FF, Russia) insecticide, at an application rate of 0.15 L/ha.Direct harvesting was carried out at the end of August.
The fat content in oilseeds of spring rapeseed was determined by the Soxhlet method.The essence of the method is to wash out the fat with a solvent.Subsequently, the determination of the mass difference of the dry flask, and the flask after extraction with a fat content.The concentration of photosynthetic pigments wavelength using a KFK-3M strophotometer.The data obtained during the experiments were processed using mathematical methods of variation statistics using the Microsoft Excel software and Statistika 6; we used the Student-Fisher method; the threshold of reliability of the obtained data is designated as (p<0.05).

Results
Single-spray fertilization reduced the vegetation season duration by 2-3 days, and doublestaged feeding reduced the vegetation season timing by 3-5 days.This effect was manifested by the time of seed ripening.Because of the microelement sufficiency, vegetative plants were able to synthesize a full complex of enzymes, which in turn had a favorable effect on the acceleration of biochemical reactions and, as a consequence, was a factor in reducing the vegetation season duration.
The mass and overall size of plants during the growing season are closely related to the elements of nutrition and the overall fertility of the soil.By using nutrients, plants increase their vegetative mass.It is the use of non-root fertilizing with microfertilizers that makes it possible for plants to develop at a faster pace, increasing their size.Micronutrient fertilizers studied in the trial contributed to the growth of the vegetative mass of plants.It was revealed that the general weight of 5 plants in the green pod stage was the smallest in the control option (65.9 g).Of all the micronutrient fertilizers studied in the trial, the greatest effect was observed when vegetating plants were processed twice with the preparations Plantafol 20:20:20 and Plantafol 5:15:45, exceeding the weight of plants in the control option by 79.8 g and 71.5 g, respectively.
The lack of trace elements in the soil can cause a decrease in the speed and consistency of the processes responsible for the development of the plant organism and as a result lead to diseases and even cause the death of plants.Single-spray feeding with these micronutrient fertilizers in the rosette and bud-formation stages provided an increase in the vegetative mass compared to the rest of the studied options.The minimum weight gain was observed when plants were processed with Boroplus; the average weight of five plants was 83 grams.Foliar feeding of spring oilseed rape plants contributed to an increase in plant density.This indicator varied in the range of 215.2-249.7 pcs/m2 for the options the application of micronutrient fertilizers.The maximum plant density was observed in the feeding option with Plantafol 20:20:20, yeilding 249.7 plants/m2.
Boron is one of the main nutrients for the normal growth of higher plants.In the micronutrient fertilizers under study, boron was part of all preparations, except for Lignohumate Thus, feeding plants with Boroplus increased the number of pods by 6.3 pcs.compared with the control option, but this increase was the smallest in comparison to the rest of the studied options.A crop needs a full range of microelements to maximize its productive potential.
The application of micronutrient fertilizers had practically no effect on the mass of 1000 seeds, which ranged within 3.33-3.42grams.Foliar feeding with micronutrient fertilizers influenced plant height.This is due to the fact that the trace elements that make up the fertilizer functioned as biological accelerators and regulators of complex biochemical processes.Plantafol 20:20:20 and Plantafol 5:15:45 include the full complex of micronutrients; the application of these preparations in all fertilization periods was positive and had an intense effect on the oilseed rape growth and development.
Our research found that the treatment of plants with microfertilizers contributed to the accumulation of pigments.Thus, the maximum accumulation of pigments was noted on the rapeseed plants processed twice; on average, for the research options, this indicator was 1.216 ± 0.0100 mg/gram of wet weight; for the control option, it was 0.701 ± 0.0099 mg/g of wet weight.This is due to the fact that microfertilizers are able to increase the activity of all cells, and this leads to an intensification of metabolism, photosynthesis and respiration of plants, which is a factor in the accumulation of photosynthetic pigments in the plant.All biometric indicators of the yield structure were higher in all the studied variants when processing plants in the budding phase than in the rosette phase.This is due to the fact that the microelements contained in microfertilizers are needed more by plants at the time of laying generative organs.Treatment of spring rapeseed plants with microfertilizers in the budding phase increases such indicators as the number of flowers, lateral shoots, improved pollination, increased pods and uniformity of their maturation.And the applied treatment with microfertilizers in the rosette phase contributes more to strengthening the root system, ensures the resistance of plants to root rot and to adverse factors, and generally gives protection to plants in the early stages of development.

Discussion
The use of foliar top dressing with microfertilizers was an additional reserve for increasing productivity.It is well known that in the cultivation of rapeseed, mineral nutrition is used only of the first order: nitrogen, phosphorus, potassium.However, rapeseed is also sensitive to the lack of sulfur, boron, magnesium, copper and manganese, as well as molybdenum and zinc.The lack of these trace elements causes a violation of carbohydrate metabolism, the synthesis of protein substances, reduces the resistance of plants to disease.Their use in the cultivation of rapeseed is one of the reserves for increasing productivity and improving the quality of products and does not require much labor.Microelements that are part of microfertilizers are absorbed by the plant through the leaves, affect photosynthesis, strengthening it, activate the activity of enzymes, biochemical processes in plants, which makes it possible to obtain a higher yield.The average crop yield of spring oilseed rape plants treated in the rosette stage according to the research options was 1.59 t/ha, amounting to1.69 t/ha when treated in the bud-formation stage and 1.85 t/ha with doublestaged fertilization, in the control option it was 1.40 t/ha.
The maximum increase in the yield was provided by Plantafol 20:20:20 and Plantafol 5:15:45 with double-spray fertilization, amounting to 2.05 and 1.94 t/ha, respectively, and exceeding the control 1 by 0.64 and 0.53 t/ha.Crop yield of spring oilseed rape in the studied options strongly depended on the number of pods on the plant, the plant height before harvesting, and the number of plants per 1 m2.The correlation coefficient for these options was r = 0.91±0.10,r = 0.8±0.10,and r = 0.79±0.10,respectively.
The application of micronutrient fertilizers had a similar effect on the oil content of rape seeds.This indicator ranged within 43.73-43.77%.We noted a tendency for increasing oil accumulation in rape seeds only by 0.02-0.04%,which, according to the research options, The gross oil harvest is an important indicator for spring oilseed rape; it depends on the crop yield and oil content.The application of Boroplus and Lignohumate provided a smaller effect on the gross oil harvesting, the gain compared to the control option was 18.2% and 34.8%, respectively (foliar feeding in the rosette stage).The maximum gross oil yield was provided by double-staged fertilization.The largest amount of oil was collected when plants were treated with Plantafol 20:20:20 (0.77 t/ha), slightly less oil was obtained in the options of feeding with Life Force (0.71 t/ha) and Plantafol 5:15:45 (0.72 t/ha).This is caused by the more diverse micronutrient composition of Plantafol.Precisely the compositions of microelements can ensure the normal functioning of vegetative objects, and contribute to an increase in crop yield and oil content.Application of complex inorganic or organic fertilizers have been shown to increase plant growth and productivity in different crops.

Conclusion
The effectiveness of foliar fertilizing with microfertilizers was evaluated by such indicators as increasing the yield of spring rapeseed, improving the quality of oilseeds, increasing the gross oil harvest per hectare and reducing the cost of finished products.
All micronutrient fertilizers studied in the experiment had a positive effect on crop yield.Micronutrient fertilization of rapeseed plants in the rosette stage contributed to increased productivity by 13.5% on average for research options, increasing it by 20.7% in case of feeding in the bud-formation stage and by 32% in case of double-spray application compared to the control option.Double-spray fertilization with Plantafol 20:20:20 and Plantafol 5:15:45 provided the maximum increase in the yield, amounting to 2.05 and 1.94 t/ha, respectively, and exceeding the control option by 0.64 and 0.53 t/ha.
The application of micronutrient fertilizers had a positive effect on the oil content of rape seeds.This indicator ranged within 43.73-43.77%.The maximum gross oil yield was provided by double-spray fertilization.The largest amount of oil was collected when plants were treated with Plantafol 20:20:20 (0.77 t/ha), slightly less oil was obtained in the options of feeding with Life Force (0.71 t/ha) and Plantafol 5:15:45 (0.72 t/ha).
Besides that the treatment of spring rapeseed plants with microfertilizers contributed to the reduction of the vegetation season.Single-staged fertilizations reduced its duration by 2-3 days, while double-spray fertilizations reduced its duration by 3-5 days, what is important in the technology of rapeseed cultivation.
Studies conducted in the experiment have established high productivity and economic efficiency in foliar treatment of spring rapeseed plants in the rosette phase and the subsequent budding phase with Plantafol 20:20:20 microfertilizer at a dose of 1 kg/ha in the Central Black Earth Region of Russia.
Further research is needed to determine the best combinations of the studied microfertilizers to assess their impact on the productivity of spring rapeseed plants.There is also a need to identify changes that occur at different stages of plant development, using biochemical analyses.