Biological Nitrogen Fixation for Sustainable Agriculture Development Under Climate Change–New Insights From a Meta-Analysis

Biological nitrogen fixation (BNF) in legume crops is a crucial ecosystem service that enhances soil nitrogen and reduces the need for chemical fertilisers. This study evaluates the factors influencing the proportion of plant nitrogen derived from atmospheric fixation (Ndfa) in legume crops. We compiled a global dataset spanning from 1980 to 2018 and used the ¹⁵N method to assess the impacts of crop species, climatic conditions, stand composition and nitrogen fertilisation on Ndfa. The global meta-analysis reveals that the percentage of nitrogen derived from atmospheric fixation (Ndfa) in legumes ranges from 5% to 99%, with an average of 68%. Fodder legumes exhibited higher Ndfa, averaging 75%, while grain legumes showed more variability, ranging from 38% to 85%, depending on species and climatic conditions. The significant variability in Ndfa underscores the complexity of the process, which is influenced by species-specific traits, ecological conditions and competition in mixed stands. However, the current data is insufficient for precise Ndfa estimation in nitrogen balances and decision support tools. The study highlights the need for further research on the impact of nitrogen fertilisation and stand composition on Ndfa. These findings emphasise the potential of BNF to support sustainable agriculture by improving nitrogen availability and reducing dependence on synthetic fertilisers and particularly susceptibility to climate change challenges. To optimise the benefits of BNF, future research should focus on refining fertilisation regimes and exploring species-specific responses to various ecological conditions. Exploring adaptive strategies, like selecting drought-tolerant legumes and optimising irrigation, is essential. This will enhance the application of BNF in diverse agricultural systems, contributing to more sustainable and efficient farming practices.