Abstract

Background The demand for estimates of biological nitrogen (N) fixation inputs in agricultural systems is driven by the need to effectively manage the global N cycle.Scope We present a methodology for quantifying N-2 fixation by the grain legume-rhizobia symbioses that can be used for any year or sequence of years for which area and production statistics for legume oil-seed and pulse crops were available and at country-to-global scales. The coefficients used in the templates - harvest index, N harvest index, %N shoots, %N grain and a factor to account for below-ground N - were aggregated from 224 reports containing > 4,000 observations. Values for the % total crop N derived from atmospheric N-2 (%Ndfa) for specific grain legumes and regions were determined in a companion paper. The grain legumes were estimated to fix a global total of 35.5 Tg N in the year 2018 - 25.0 Tg for soybean (Glycine max), 7.2 Tg for the pulses and 3.3 Tg for groundnut (Arachis hypogaea). Soybean dominated global grain legume N-2 fixation, with 38 % of total N fixed associated with soybean in South and Central America and a further 22 % by soybean in North America.Conclusions The updated estimates of N-2 fixation by the grain legumes inform us of a substantial and increasing role that biological N-2 fixation plays in global agricultural systems. The challenge remains to reliably estimate N inputs from other N-2-fixing organisms that are active in these systems.

Keywords

Nitrogen fixation; regional; global estimates; templates; legumes; pulses; oilseed legumes; rhizobia; soybean

Published in

Plant and Soil
2022, Volume: 474, number: 1-2, pages: 1-15
Publisher: SPRINGER

SLU Authors

• Jensen, Erik Steen

  • Department of Biosystems and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science


Publication identifier

DOI: https://doi.org/10.1007/s11104-021-05166-7

Permanent link to this page (URI)

https://res.slu.se/id/publ/122615