© The Authors, published by EDP Sciences, 2020

1 Introduction

Due to continuous increase in the cost of mineral fertilizers and possible negative effects on product quality and the environment, it is important to find ways to reduce their doses without losing their efficiency. According to some scientists [1, 2], the use of biological preparations made on the basis of effective microbial strains is becoming ever more relevant. It is proposed to use them not only for pre-sowing seed treatment of seeds or vegetative plants, but directly applying them to mineral fertilizers during planting (biomodified fertilizers). According to the authors, the latter allows reducing the doses of fertilizers and increasing the utilization rates of their nutrients, as well as improving plant nutrition.

The above led to the purpose of the study, i.e. to study the impact of mineral and biomodifiedfertilizers on the formation of oat yield.

2 Materials and methods

The study was carried out on a stationary site of the experimental field of Ulyanovsk Agricultural Research Institute – Branch of Samara Federal Research Center of the Russian Academy of Sciences in 2016–2018 in grain crop rotation: complete fallow – winter wheat – spring wheat – barley – oat. The soil of the experimental field contains leached heavy loamy chernozem with humus content of 6.43–6.62%, available phosphorus and potassium compounds (according to Chirikov) – 214–228 and 101–117 mg/kg of soil, pH_KCl – 6.3–6.8 units.

Research objects:

• azophosca – mineral fertilizer containing 15% nitrogen, phosphorus and potassium (NPK);

• bisolbifit – microbiological preparation based on rhizosphericbacteria strain BacilliusSubtilis Ch–13. Bacteria cam synthesize substances that inhibit the development of plant pathogenic fungi and bacteria, as well as substances that stimulate plant growth. Pre-sowing treatment of seeds with Bisolbifitebiopreparation (dry form) was carried out 1 day prior to sowing at the rate of 400–600 g/t, consumption of working solution – 10 l/t;

• biomodified fertilizer (NPK_m ½ and NPK_m). A dryform of BisolbiFitbiopreparation was used to prepare abiomodified fertilizer at a rate of 4 kg per 1 ton of fertilizer. The biopreparation was applied to a mineral fertilizer on the day of its application to the soil.

The field experiment was carried out according to the developed scheme (Table 1). The efficiency of fertilizers was evaluated in 3 backgrounds. The first background remained as a control (zero, absolute control), the second included ammonia nitrate in a dose of 40 kg/ha treated with Bisolbifitebiopreparation, the third – ammonia nitrate in a pure form in a dose of 40 kg active ingredient/ha introduced for pre-plant cultivation.

The accounting area made 100 m² (4*25), triple application, random location. The organization of field experiments, selection of soil and plant samples, observations and laboratory analyses were carried out according to corresponding GOST standards.

3 Results and discussion

The change of the crop yield structure makes it possible to identify those elements that prevail in the formation of yields in specific soil-climatic conditions [3–5]. At the same time, it is necessary to analyze the dynamics of each element of crop productivity, which participates in yield formation. Table 2 shows the oat yield structure in experiments.

The main basic component of yield formation is the optimal number of productive stems per unit area [6, 7]. The correlation dependence of oat grain yield with this indicator made 0.76. Depending on the dose and type of fertilizer, the number of productive stems varied within 273–311 pcs/m² in the control option, 297–315 pcs/m² in the option with BisolbiFit (pre-sowing seed treatment), 300–320 pcs/m² in the option with Azophosca in its pure form (N₁₅P₁₅K₁₅), 312–157 pcs/m² in the option N₁₅P₁₅K_15m and 314–317 pcs/m² in the option ½N₁₅P₁₅K_15m. The highest number of productive stems per 1 m² was observed for N₁₅P₁₅K_15m and N₁₅P₁₅K₁₅ in background 2 – NH₄NO_3m (Table 2).

The structural indicator “number of grains in a panicle” plays a certain role in yield formation. On average over 3 years of study, the minimum number wasnoted in control options of all studied backgrounds, respectively: 23.9 pieces; 24.2 pieces; 24.1 pieces. In all options that used mineral and modified fertilizers were characterized by the largest amount of grains. In the option with biopreparation, the number of grains in a panicle varied from 24.3 to 25.4 pieces.

A direct bond (r=0.97) was noted in the analysis of such indicators as the “number of grains in a panicle” and the “weight of grains in a panicle”. Consequently, these grain quality indicators have similar changes depending on the type of fertilizer.

The weight of 1000 grains characterizes the degree of grain ripeness, density of its tissues and the amount of endosperm in a grain, which impacts sowing and commercial qualities of grain [3, 5]. Over the years of study, the weight of 1000 grains fluctuated in the range of 35.6–-38.8 g. Without the use of mineral fertilizers and biopreparation in a zero background it amounted to 35.6 g; 37.2 g in NH₄NO_3m and 37.0 g in pure ammonium nitrate. The application of fertilizers positively affected the studied indicator thus increasing its value by 0.8–1.6 g. Compared to the zero background, the weight of 1000 grains after the application of mineral, biomineral fertilizers and biopreparation increased in NH₄NO_3m background from 37.2 to 38.8 g and from 37.0 to 38.0 g in NH₄NO₃ background.

The correlation analysis made it possible to establish the dependence of yield on the main elements of oat yield structure. Such indicators as the “number of productive stems – yield”, “weight of grains in a panicle – yield”, “weight of 1000 grains – yield” and the “number of grains in a panicle – yield” are marked by direct correlation, which coefficients made 0.76, 0.86, 0.88 and 0.81 respectively (Fig. 1).

Grain yield is the main indicator in the evaluation of studied plant cultivation techniques. Its formation largely depends on plant growing conditions. In the process of growth and development, certain requirements are placed on external environmental conditions, which are related to the nature and intensity of physical and biochemical processes. One of the most effective and fast-acting factors improving plant nutrition and increasing oat yield is the use of mineral fertilizers. In recent decades, microbiological preparations, which due to their additional involvement in agrocenosis of the main elements of mineral nutrition, also contribute to the increase of grain productivity of the culture, is considered a promising direction [3, 8].

As a result of our studies over 2016-2018, there was a positive effect of mineral and biomodified fertilizers, as well as biopreparations on the oat yield. On average over 3 years the yield of oats grain (Table 3) varied from 2.15 to 2.71 t/ha, without fertilizers it made 2.24 t/ha, with NH₄NO_3m – 2.57 t/ha and NH₄NO₃ – 2.38 t/ha.

Without the use of mineral fertilizers and biopreparations the grain yield reached 2.15 t/ha, in the background of NH₄NO_3m – 2.43 t/ha and in the background of ammonium nitrate in pure form – 2.25 t/ha (Table 3). The use of azophoska increased yields in all studied backgrounds by 0.13, 0.18 and 0.15 t/ha,respectively. Biomodification of mineral fertilizer (N₁₅P₁₅K_15m) contributed to further increase of oat yield.

The use of a half-dose biomodifiedazophoska(½N₁₅P₁₅K_15m) increased grain yields relative to theabsolute control by 0.13 t/ha (background 1), 0.49 t/ha (background 2) and 0.24 t/ha (background 3).

It was also found that a higher yield was formed in the background with ammonium nitrate (NH₄NO_3m) at a dose of 40 kg active ingredient/ha treated with microbiological preparation BisolbiFit.

The efficiency of any crop cultivation approach is characterized not only by yield, but also by the quality of its products. Table 4 shows the assessment of oat quality caused by grain biochemical composition.

In the control option the protein content in 3 studied backgrounds made respectively: 12.4, 12,0, 12,1%. The studies showed that the increased yields led to a certain decrease of protein content in oat grains, which ranged from 11.3 to 12.4% and on average made 11.8%. At the same time the lowest values of protein content in grain were observed in 2016 (10.9–11.6%), which is caused by established conditions of culture vegetation. In 2018, the amount of it in the grain was maximum and varied from 12.4 to 13.2%.

The correlation analysis showed that the weight of 1000 grains is in positive relation with yield and revealed a negative relation between yield and protein content in oat grain (r=−0.76) (Figure 2).

Besides, the assessment of the qualitywith BisolbiFit biopreparation of oat grain shall consider such characteristics as grain-unit and hoodness. The mineral nutrition of plants also influenced the grain-unit: on average over the years of study it varied from 466 to 490 g/l. In the control option it made 470–478 g/l, in the option with BisolbiFit biopreparation (pre-sowing seed treatment) – 472–482 g/l, in the option with azophoska (N₁₅P₁₅K₁₅) – 480–488 g/l, in N₁₅P₁₅K_15m – 478–490 g/l, and in the option ½N₁₅P₁₅K_15m – 474–488 g/l. In the 2 background with modified ammonium nitrate under pre-sowing cultivation, the largest amount of grain-unit was in option No. 4 (N₁₅P₁₅K_15m) – the grain was more filled and coarse with a minimum percentage of hoodness compared to other options. It seems that not only films themselves, but also the magnitude of the air voids between them, as well as between shells and seed kernel, are important.

Besides, oat availability depends on hoodness. Under different nutritional conditions of a plant this value decreased, its decrease to 27.3% was observed for option N₁₅P₁₅K_15m. The use of mineral fertilizers and biopreparation influenced grain hoodness, the lowest percentage of hoodness was observed for the option N₁₅P₁₅K_15m in all studied backgrounds and made 27.3%, 25.8%, 27.0%, which is 4–5% lower than the control. Pre-sowing seed treatment did not have a significant impact on this indicator. The maximum value of grain hoodness was observed in the control option: 33, 30, 31%.

Fig. 1. Dependence of oat yield on yield structure elements, 2016-2018

Fig. 2. Dependence of grain protein content on the weight of 1000 grains

4 Conclusion

1. The use of biomodified Azophoska significantly increased oat grain yield in zero background by 6–7%, in the background with biomodified ammonium nitrate under pre-plant cultivation by 9–12% and in the background with ammonium nitrate in pure form – by 6–11% compared to traditional fertilizers.

2. The correlation analysis made it possible to establish the dependence of yield on the main elements of the oat yield structure. Such indicators as the “number of productive stems – yield”, “weight of grains in a panicle – yield”, “weight of 1000 grains – yield” and the “number of grains in a panicle – yield” are marked by direct correlation, which coefficients made 0.76, 0.86, 0.88 and 0.81 respectively.

3. The mineral nutrition of plants influenced the grain-unit: on average over the years of study it varied from 466 to 490 g/l. The lowest percentage of hoodness was observed for the option N₁₅P₁₅K_15m in all studied backgrounds and made 27.3, 25.8, 27.0%, which is 4–5% lower than the control.

References

All Tables

All Figures

	Fig. 1. Dependence of oat yield on yield structure elements, 2016-2018
In the text

	Fig. 2. Dependence of grain protein content on the weight of 1000 grains
In the text