Biological nitrogen fixation and microbial technologies for plant nitrogen nutrition: mechanisms, efficiency and prospects

Abstract

Biological nitrogen fixation (BNF) is one of the most fundamental and ecologically significant biogeochemical processes on Earth, providing atmospheric nitrogen input into terrestrial bioecosystems. In the current era of intensive agriculture, where global consumption of synthetic nitrogen fertilizers exceeded 116 million tons in 2025 (International Fertilizer Association, 2025), the problem of persistently low nitrogen use efficiency (NUE 40–55%) and its severe environmental consequences has become critically urgent. These consequences include massive nitrate leaching, eutrophication of water bodies, substantial emissions of nitrous oxide (N2O) — a potent greenhouse gas, and progressive degradation of soil fertility. Despite considerable scientific advances in understanding the mechanisms of BNF, many important aspects remain insufficiently explored. These include the long-term stability and field performance of microbial consortia, the influence of climate change on symbiotic and associative interactions, the vertical stratification of diazotrophic communities in soil profiles, and the regional peculiarities of implementing microbial technologies in countries with complex soil and climatic conditions, particularly Ukraine, whose agroecosystems have been significantly affected by the ecological consequences of military actions. The aim of this review is to systematically summarize and critically analyze contemporary scientific knowledge on biological nitrogen fixation and microbial biotechnologies for plant nitrogen nutrition. The paper examines the underlying mechanisms, agronomic, ecological, and economic efficiency of these technologies, and evaluates their practical implementation prospects within the global context and the specific conditions of Ukrainian agroecosystems. The review was conducted in the narrative review format based on peer-reviewed publications from 2015–2025 indexed in Scopus, Web of Science, PubMed, and Google Scholar. Special attention is paid to recent meta-analyses, systematic reviews, and large-scale experimental studies that reflect the current state of the field. The article discusses the global «nitrogen paradox», the main types of biological nitrogen fixation (symbiotic, associative, endophytic, and free-living), the molecular basis of the nitrogenase complex, and the evolution of microbial technologies — from classical single-strain inoculants to advanced synthetic microbial communities (SynCom). Key challenges and limitations of widespread adoption are thoroughly analyzed, including high variability of results, competition with indigenous microbiota, regulatory barriers, product quality issues, and socio-economic constraints. It is demonstrated that microbial technologies possess substantial potential as a strategic tool for transitioning toward sustainable, resourceefficient, and climate-neutral agriculture. They can significantly reduce dependence on synthetic fertilizers, lower greenhouse gas emissions, enhance soil health, improve nutrient cycling, and increase the overall resilience of agroecosystems. However, realizing this potential requires an integrated approach that combines precision agriculture, regenerative practices, regionally adapted microbial solutions, and supportive policy frameworks.