Wang, YinliuHasi, MuqierBu, DongdongLi, AngXue, JianguoWang, ChanghuiTian, QiuyingNiu, GuoxiangGeng, QianqianWang, LixinHuang, Jianhui2023-03-222023-03-222021Wang, Y., Hasi, M., Bu, D., Li, A., Xue, J., Wang, C., Tian, Q., Niu, G., Geng, Q., Wang, L., & Huang, J. (2021). Nitrogen addition results in Medicago sativa switching nitrogen sources. Plant Ecology & Diversity, 14(3–4), 183–194. https://doi.org/10.1080/17550874.2021.20073091755-0874, 1755-1668https://hdl.handle.net/1805/32030Background Nitrogen (N) addition may have strong impacts on legume growth and their biological N fixation (BNF), but how legume N acquisition sources respond to N inputs have yet to be comprehensively assessed.Aims We quantified the effects of N addition on the growth and BNF of Medicago sativa and to assess the response of legume N acquisition to N addition.Methods We grew M. sativa in the greenhouse under gradients of added NH4NO3 and analysed the variables that were relative to growth and BNF, such as N concentration, biomass, δ15N values, nodule number, percentage of N derived from the atmosphere (Ndfa%).Results Nitrogen addition had marginal effects on plant biomass production and foliar N concentration. Foliar δ15N value increased with increasing added N, while Ndfa% decreased. The number of nodules formed also decreased with N addition while the nitrogenase (nifH)genecopies per unit nodule mass was not significantly different with N addition.Conclusions These findings indicate that increasing mineral N availability decreases symbiotic investment into BNF, mainly by reducing nodule formation; this was found to have no significant impact on plant growth because the plant changes its N source from BNF-N to mineral N derived from the soil.en-USPublisher PolicyBiological N fixationN concentrationstable isotopeδ15NArticle