The efficiency of combined application of mineral fertilizers, inoculants in soybean growing technology, and functioning of nitrogen-fixing symbiosis under increasing nitrogen rates
¹National University of Life and Environmental Sciences of Ukraine, Department of Plant Science, Heroiv Oborony Str., 15, UA03041 Kyiv, Ukraine
²SS NULES ‘Mukachevo agricultural college’, Matrosova Str., 32, UA89600 Mukachevo, Zakarpattya reg., Ukraine
³Ukrainian Institute for Plant Variety Examination, Henerala Rodymtseva Str., 15, UA03041, Kyiv, Ukraine
Soy is a valuable leguminous crop, whose productivity directly depends on many factors, among which nitrogen fertilizers are one of the most important. Nitrogen fertilizing of this crop is often given insufficient attention because the yield increase can be quite insignificant. The purpose of the research is to study the combined effect of biofertilizers and increasing rates of nitrogen mineral fertilizers on the growth, development, and yield of soybean varieties. The experiment is three-factorial: factor A – early ripening soybean varieties Annushka and Ustya, factor B – seeds inoculation by biofertilizer, and factor C – rates of mineral fertilizers application. Results of research show the efficiency of nitrogen-fixing symbiosis during seed inoculation was established for nitrogen rates from N0 to N60 against the background of P60K60 – the biomass of nodule bacteria is 418–675 mg plant-1. The application of N90P60K60 significantly reduces the number and mass of nodule bacteria – 207–241; N120P60K60 – 32.0–42.0 mg plant-1, and with the introduction of P60K60 + N150–180 nodule bacteria are not formed and the effectiveness of microbiological drugs is not recorded. Nitrogenase activity with N0–90 application on the background of P60K60 and seed inoculation ranged from 3.25 to 7.76 μmol C2H4 per plant ha-1. With a further increase in nitrogen levels, nitrogenase activity was not recorded. On typical chernozems of the Forest-Steppe of Ukraine, higher yields of early-ripening soybean varieties are formed by applying N60P60K60 and pre-sowing seeds treatment with rhizohumin or rhizohumin/hetomics combination. P60K60N150–180 showed a partial decrease in soybean yield due to the distress effect.