Relevance of research.To increase the effectiveness of symbiotic fixation in recent years, the complex inoculation of legume seeds with nodulousbacteria along with endophytic bacteria is used.However, the issue of the inoculant use effectivenessbased on rhizobia and endophytic bacteria is still not well studied enough.So, an assessment of their effectiveness is extremely important for the further development of existing scientific knowledge about the microbial and plant symbiosis of leguminous crops. Along with the above, the involvement of nitrogen from the air into the nutrients circulation by legumes provides the ecological improvement of the environment.
The purpose of scientificresearches is to specify the effectiveness of the effect of complex inoculation of seeds by the strains of nodulous and endophytic bacteria on the yield of different varieties of soybean under the irrigatedconditions of the southern Steppe zone of Ukraine.
Materials and methods of research.Two-factor field experiment is based on the split plot method in a four-time repetition, where the main plots (first-order plots), factor A – varieties of soya: ultra-fast-growing –Diona and mid-growing –Aratta, subplots(second-order plots), factor B –inoculation of seeds with different strains of nodulous and endophytic bacteria: Control 1 (without seed water treatment); Control 2 (seed water treatment); RyzobinK(association of three strains of Bradyrhizobiumjaponicum: B.japonicum of УКМВ-6018, УКМВ-6023, УКМВ-6035); RyzobinK+ Ranibacillus sp.1; RyzobinK + Bacillus sp.4; RyzobinK + Brevibacillus sp.5; RyzobinK + Pseudomonas sp.6; RisobinK + Bacillus megateriumУКМВ-5724.Soybean sowing was carried out in the third decade of April with a seeder «Клен» with a rows width of 45 cm to a depth of 6 cm. The seed rate of Diona varietyis 800000 and Aratta– 600000 similar seeds per 1 hectare.
The influence of weather and climatic conditions on the soybean crop formation was specified by determining the potential evaporation, moisture deficit and humidity coefficient. The evaporation and lack of moisture supply during the interphase periods of studied soybean varieties significantly changed and depended on the average daily temperature and relative air humidity and the amount of precipitation fallen during the growing season.
Results of the research and their discussion.The application of strains of nodulous and endophytic bacteria during inoculation of seed material significantly influenced the yield of different soybean varieties. On average, in 2017-2018, the highest yield of soybean seeds was obtained from pre-sowing inoculation with nodulous bacteria, which is the basis of RisobinK, in combination with endophytic bacteria.In particular, the maximum yield of Dionavariety was formed during pre-sowing inoculation of seeds RisobinK + Bacillus sp.4 – 3,12 t/ha, Aratta variety – 2,55 t/ha. The high yield of soybean Diona variety – 2,85 t/ha and Aratta variety – 2.40 t/ha were also obtained for inoculation of seeds by the bacterial complex RisobinK + Brevibacillus sp.5. The lowest yield of both sorts of soy was obtained in the version Control 1 (without seed treatment with water) – 2,27 t/ha Diona variety and 2,13 t/ha –Aratta variety.
Conclusions.Thus, the seeds crop formation of different varieties of Diona and Aratta soybeans under the conditions of regional dry (95%) climate change in 2017-2018, significantly depended on the hydrothermal conditions of the vegetation period and the symbiosis of nodulous and endophytic bacteria on the irrigated land of the southern subzone Steppe of Ukraine.Pre-sowing inoculation of soybean seeds varieties with the nodulous and endophytic bacteria, in comparison with the control variants, significantly influenced the formation of soya varieties crop, and increased the yield of Dionavariety by 0,58-0,85 t/ha and the Aratta variety – 0,27-0,42 t/ha.
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