02209nam a2200265 a 450000100080000000500110000800800410001902200140006002400520007410000210012624500810014726000440022852014590027265000190173165300260175065300170177665300160179370000210180970000230183070000160185370000210186970000220189070000170191270000140192921669442024-08-30       2024    bl uuuu     u0uu1 u    #d  a0334-51147 ahttps://doi.org/10.1007/s13199-024-00988-22DOI1 aAMBROSINI, V. G.  aEnvironmental variables controlling biological nitrogen fixation in soybean.  aSymbiosis, v. 93, p. 43-55, 2024.c2024  aThe effect of environmental factors on the proportion of the nitrogen (N) derived from the atmosphere (Ndfa) in soybean [Glycine max (L.) Merril] have been traditionally approached individually given their intrinsic complexity. Alternatively, a more in-depth investigation of such complex interactions can be pursued by delimiting environments where Ndfa is uniform. Thus, the aim of this study was to define environments on 24 sites by extensively characterizing weather, plant, and Ndfa related traits to find discriminant variables defining three Ndfa classes (low, medium, and high). The Ndfa was determined at the beginning of the seed filling (R5 growth stage) using the 15N natural abundance method. Twenty environmental vari ables were utilized to categorize Ndfa in low (&lt 57%), medium (57–66%), and high (≥ 66%) classes via implementation of discriminant multivariate analysis. The Ndfa averaged 60%, lower to previous values reported for Brazil (ranging from 69 to 94%). Mean air temperature, associated to SOM and soil N, was the most important variable related to low Ndfa, while improving soil fertility (soil pH, base saturation, exchangeable Ca and Mg, and available P) was critical for high Ndfa and, consequently, seed yield. The high contribution of those factors highlight the importance of implementing strategies to improve soil fertility, to promote better plant growth, and thus enhancing Ndfa contribution to crop N uptake.  aSoil fertility  a15N natural abundance  aField trials  aN2 fixation1 aCIAMPITTI, I. A.1 aFONTOURA, S. M. V.1 aTAMAGNO, S.1 aMORAES. R. P. de1 aSCHWALBERT, R. A.1 aURQUIAGA, S.1 aBAYER, C.