The effectiveness of the use of associative diazotrophs to increase the yield of spring triticale

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Institute of agricultural microbiology and agroindustrial manufacture of the NAAS

The effectiveness of the use of associative diazotrophs to increase the yield of spring triticale

Annotation

Goal. To study the effectiveness of the use of associative Azospirillum brasilense diazotrophs 10/1 to increase the yield and improve grain quality of spring triticale. Methods. Microbiology, gas chromatography, field experiment, and statistical.

The objects of study - plants of spring triticale of varieties Oberig Kharkivskii, the strain of associative nitrogen-fixing bacteria Azospirillum brasilense 10/1. Field experiments were carried out in conditions of Ukrainian Polissia (Institute of Agricultural Microbiology and Agroindustrial Manufacture, NAAS, Chernihiv). The inoculation of seeds of triticale was carried out with 3-days culture of bacteria A. brasilense 10/1 for 2 h before seeding at the rate of 200-300 thousand bacterial cells per seed. Processing of experimental data was performed using the computer program Microsoft Office Excel.

Results. It is established that the strain A. brasilense 10/1 positively influenced the growth and development of spring triticale due to improved nitrogen nutrition of plants and the ability to produce growth-stimulation substances. Use of the strain A. brasilense 10/1 for preplant bacterization of seeds triticale provided the increase in crop yield by 0.5 t/ha, or of 16.39% compared to control. Positive influence is revealed on a mass of grains in one ear and weight of 1000 grains. These indicators increased in the variant with inoculation on average on 16.8 and 11.9%, respectively. Also, by inoculation of spring triticale with a promising strain of A. brasilense 10/1 the protein content in the grain increased to 14.06%, wet gluten - to the 35, 17, full-scale mass of grain increased by 7.3%.

Conclusions. Taking into account the positive effect of associative nitrogen-fixing bacteria A. brasilense 10/1 on the growth and development of triticale plants, perspective variant is the creation of a biological product based on the strain for increasing the yield and improving the quality of the resulting products.

Key words: Azospirillum brasilense, nitrogen-fixation, inoculation, biological preparation, structural indicators of the crop.

Introduction

Triticale was first selected in the late nineteenth century in order to combine the best qualities of wheat and rye [1]. This crop exceeds both parent plants in a number of key features (yield, nutritional and biological value), and in terms of resistance to adverse weather conditions and disease, significantly exceeds wheat and is not inferior to rye [2, 3]. Due to the larger number of grains in the ear, triticale forms a much higher productivity compared to wheat [1]. The plant is widely applied in the national economy as a forage, food and fodder crop [4, 5].

Today, triticale is successfully grown in many countries on an area over 4 million hectares, and world triticale grain production is over 17 million tons. In Ukraine, triticale sown areas reach 100,000 hectares annually [6, 7]. It is known that there is a direct relationship between the level of agrochemicals and the gross harvest of agricultural products [8, 9]. However, in Ukraine there is a negative balance of humus and nutrients [10]. Triticale belongs to the crops that are undemanding to soil fertility, but depends on the level of mineral nutrition, which significantly affects the formation of the productivity of their agrocenoses [1, 11]. Price escalation for mineral fertilizers necessitate the search for alternative sources of plant nutrition. One of the areas of environmentally friendly agriculture is the use of microbial preparations that have a positive effect on plant growth and development, as well as soil fertility [12-14].

Fixation of molecular nitrogen in the atmosphere is one of the most important biochemical processes, which significantly affects soil fertility and supply of plants with biological nitrogen [13-15]. One of the most active associative diazotrophs are representatives of the genus Azospirillum, which form effective associations with plants of wheat, rye, barley, buckwheat, etc. and are successfully used as bioagents of microbial preparations to increase the yield of above crops [14].

Considering the above, the objective of our research was to study the efficiency of the use of associative diazotrophs Azospirillum brasilense 10/1 to increase yields and improve quality of spring triticale grain.

Materials and methods. The objects of study were spring triticale Oberih Kharkivskyi cultivar, a strain of associative nitrogen-fixing bacteria Azospirillum brasilense 10/1 [16], selected by analytical selection as promising for inoculation of spring triticale.

Field experiments were conducted in the conditions of Polissia of Ukraine (Institute of Agricultural Microbiology and Agroindustrial Manufacture of NAAS, Chernihiv) on leached chernozem (pH - 6.0; humus content - 3.5%; easily hydrolysed nitrogen (according to Cornfield) - 95 mg; mobile forms of phosphorus (P2O5) (according to Kirsanov) - 251 mg; exchangeable potassium (K2O) (according to Kirsanov) - 108 mg per 1 kg).

The sowing rate of triticale is 5 million similar seeds per hectare. Method of sowing - narrow-row, with a row spacing of 15 cm. The size of the experimental plot is 8 m², the size of the accounting plot is 1 m², the repetition is fourfold, the placement of plots is randomized. Seed inoculation was performed with a three-day culture of A. brasilense 10/1 bacteria two hours before sowing at the rate of 200-300 thousand bacterial cells per seed.

Potential nitrogenase activity on washed roots of triticale plants was determined by acetylene-ethylene method using gas chromatograph Chrom-4 [17].

Harvesting and accounting was performed by the direct method (weighing products from the accounting area). In order to study the structural parameters of the spring triticale crop, 100 typical plants were selected from each variant. Plant height, ear length, number and weight of grains in the ear, weight of 1,000 grains were determined [18]. The content of nitrogen, phosphorus and potassium, protein and raw fibres in the grain was determined using an infrared spectrophotometer IKS-4250 in National Scientific Centre “Institute of Soil Science and Agrochemistry named after O.N. Sokolovsky”.

The ability of azospirilla to produce physiologically active substances has been shown by bioassays [19]. The experimental data were processed using the computer program Microsoft Office Excel.

Results and discussion

Introduction of associative nitrogen fixers in the root zone allows not only to improve nitrogen nutrition of plants by fixing atmospheric nitrogen and increasing the utilization rate of soil mineral nitrogen, but also provides a diverse positive effect of microorganisms on the plant, namely synthesis of biologically active substances, in particular phytohormones, stimulation of growth and development of the root system, lateral roots and root hairs [14].

Long-term studies of potential nitrogenase activity on washed roots of triticale plants in the field conditions showed that a promising strain of nitrogen-fixing bacteria A. brasilense 10/1 contributed to an increase in PNA (potential nitrogenase activity) more than twice, compared with the control variant.

Ability of A. brasilense 10/1 to produce growth stimulating substances has been shown on shoots of spring triticale Oberih Kharkivskyi cultivar (Fig.).

Fig. Gain of dry aboveground weight of spring triticale shoots of Oberih Kharkivskyi cultivar after treatment with culture liquid of A. brasilense 10/1 (laboratory experiment)

diazotroph azospirillum growth spring triticale

As evidenced by the data shown in Fig., the most significant increase in dry aboveground weight of shoots compared to control (seed treatment with sterile water) was registered after dilution of the culture liquid of the strain in a ratio of 1:50 and amounted to 36.2%. Further dilution of the culture liquid was accompanied by a decrease in weight gain.

Analysis of the results of field experiments showed a stable probable increase in yield of spring triticale from pre-sowing inoculation of seeds with A. brasilense 10/1, which averaged 0.5 t/ha or 16.39% to control.

The structural analysis of the yield showed that pre-sowing inoculation of spring triticale with A. brasilense 10/1 contributed to an increase in plant height by an average of 1.7 cm (Table 1).

Table 1

Structural parameters of the yield of spring triticale after inoculation with A. brasilense 10/1, average 3-year data (M±m, n=3)