Investigation of nitrogen fixation activity soybeans plants by mineral fertilizers foliar treatment

Abstract

The results of the study of nitrogen-fixing activity during foliar treatment of vegetative soybean plants with liquid mineral fertilizers containing macro-microelements in various forms in the foothill zone of Kabardino-Balkaria are presented. The object of research is the early ripe soybean variety SK Veda. The soil of the experimental plot is a leached, medium-thick, low-humus, heavy loamy chernozem on carbonate clays, with a humus content in the arable layer of 3.1 %, pHkcl 5.0, mobile phosphorus 7.5 and exchangeable potassium 8.0 mg/100 g of soil. Encrustation of soybean seeds was carried out using a specific film-forming agent based on soybean phosphatides with the inoculant Nitrofix. The results of studies for 2020-2022 are given. with an assessment of the dynamics of the formation of the symbiotic apparatus by the number of nodules (pcs/m2) and by the mass of nodules (g/m2) in ontogeny of the macrosymbiont. The peak of nodule formation in soybean plants of the SK Veda variety fell on the flowering phase. The highest nodulation rates were noted in the control variant: in 2020 - 306 pcs/m2; in 2021 - 408 pcs/m2; in 2022 - 96 pcs/m2. It has been shown that foliar treatment of soybean plants with nutrient deficiency correctors has an impact on nodulation rates, with differences being noted depending on the treatment time. In the variant of Polydon NPK treatment in the primordial leaf phase, the nodulation parameters were minimal in the experiment over the years of the study (86; 216; 56 pcs/m2). Treatment of SK Veda soybean plants in the primordial leaf phase with molybdenum-containing fertilizers ensures the formation of larger nodules. The values of the nodule weight in the flowering phase in the variant of the treatment of Polydon plants with molybdenum in the primordial leaf phase increased by 1.56; 2.09; 1.11 times, respectively, for 2020, 2021, 2022. Nitrogenase activity averaged 26.4-281.6 µg N2/plant.h over the years of the study hour. In the control (inoculation with nitrogen-fixing microorganisms), the activity of nitrogenase was 208.3 µg N2/plant.h. Inoculation of soybean seeds with nitrogen-fixing microorganisms and foliar treatment of plants with Polydon molybdenum increased nitrogenase activity by 35.2-19.1 % and increased protein content by 5.0-3.9 % relative to control, depending on the treatment phase.