Photosynthetic productivity of soybean as affected by inoculation and application of microfertilisers
Authors: Kozyrskyi D. V. , Trach I. V. , Sydorak I. Ya. 
Published: December 2024

Purpose. To determine the effect of seed bacterisation and foliar application of fertilisers on the photosynthetic productivity of soybean varieties in the Western Forest Steppe of Ukraine.
Methods. A field study was conducted in 2019–2022 in the fields of the Kozatska Dolyna 2006 LLC (Khmelnytsk Region). The field experiment was established according to the following design: factor A – seed inoculation: 1) without inoculation, 2) inoculation with Ryzoaktyv; factor B – soybean varieties: ‘Samorodok’, ‘Rohiznianka’, ‘Triada’, ‘Orfei’, ‘Evridika’, ‘Aratta’, ‘Azymut’, and ‘Avrora’; factor B – foliar application of fertilisers: 1) without fertilisation, 2) split application of microfertiliser Fulvohumin. The study was conducted according to general and special methods of research in crop production.
Results. Patterns of leaf area formation during the flowering period revealed the most significant effect of the applied measures in the second half of the growing season, which proves the need to carry out measures in the first half of the growing season of the crop. In the stage of bean browning, leaf area ​​in varieties ‘Samorodok’, ‘Orfei’, ‘Aratta’ and ‘Evridika’ was 39.1, 38.1, 37.6, and 37.8 thousand m2/ha, respectively. Varieties ‘Rohiznianka’ and ‘Triada’ under similar conditions had a leaf area of ​​40.0 and 40.1 thousand m2/ha. The highest indicators in the experiment were recorded in ‘Azymut’ and ‘Arvora’: 40.5 and 40.8 thousand m2/ha, respectively. Bacterisation of seeds and foliar application of fertilisers caused the change in the photosynthetic potential of soybean to the extent of their efficacy. That is, even if the studied measure improved the general condition of crops or helped plants to accumulate additional nitrogen, its effect could not be compared with the introduction of additional nitrogen in free form, which was confirmed by the analysis of parameters of the photosynthetic potential of soybean crops. In the flowering stage, the highest indicator of net productivity of photosynthesis was in ‘Samorodok’ (1.55 g/m2 per day), while the lowest it was in ‘Rohiznianka’, ‘Triada’ and ‘Aratta’ (1.12, 1.26, and 1.25 g/m2 per day, respectively). The rest of varieties had average indicators: ‘Avrora’ 1.36, ‘Evridika’ and ‘Azymut’ 1.43, ‘Orfei’ 1.48 g/m2 per day. Under the combined effect of the studied factors, the best varieties were ‘Samorodok’ and ‘Orfei’ with net productivity of 1.58 g/m2 per day.
Conclusions. Foliar application of Fulvohumin microfertiliser contributed to an increase in the leaf area in the stage of bean browning by 2.49 thousand m2/ha compared to the option of background fertilisation. The inoculation of seeds with the biopreparation Ryzoaktyv ensured an increase in this indicator by 2.92 thousand m2/ha compared to options without this measure. Due to the complex influence of these factors, the leaf area of ​​more than 42 thousand m2/ha was recorded in varieties ‘Samorodok’, ‘Triada’ and ‘Azymut’. The highest indicators in the experiment were in varieties ‘Rohiznianka’ and ‘Avrora’: 44.0 and 45,2 thousand m2/ha, respectively. Bacterisation of seeds and foliar application of humates were effective in influencing changes in the photosynthetic potential of soybean crops. In particular, in the stage of bean formation, when plants were fed with Fulvohumin, PP was 1.20 million m2/ha versus 1.11 million m2/ha in the control variant. The variants of the experiment, in which soybean plants were grown without seed bacterisation, had an average PP of 1.10 million m2/ha, while in the case of the use of the biological preparation Ryzoaktyv, it was 1.22 million m2/ha. In the second half of the growing season, the net productivity of photosynthesis also depended on the influence of the studied factors; however, their role decreased compared to the previous period. In particular, the difference in PP between the variant of foliar application of fertilisers and unfertilised variant was 0.05 g/m2 per day, while inoculation contributed to an increase in this trait by 0.08 g/m2 per day. However, these are quite insignificant differences in the accumulation of dry matter due to the sufficiently high leaf area.