Quantifying country-to-global scale nitrogen fixation for grain legumes II. Coefficients, templates and estimates for soybean, groundnut and pulses

• Published in: Plant and soil Vol. 474; no. 1-2; pp. 1 - 15
• Main Authors: Herridge, David F., Giller, Ken E., Jensen, Erik S., Peoples, Mark B.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.05.2022; Springer; Springer Nature B.V
• Subjects: Agricultural Science; Agriculture; Analysis; Beans; Biomedical and Life Sciences; Ecology; Estimates; Fixation; Glycine max; Grain; Groundnuts; Harvesting; Identification and classification; Jordbruksvetenskap; Legumes; Life Sciences; Marschner Review; Mimosaceae; Nitrogen; Nitrogen fixation; Nitrogenation; Oilseed crops; Plant Physiology; Plant Sciences; Shoots; Soil Science & Conservation; Soybeans; Symbiosis; System effectiveness; Australia; Netherlands; Sweden; soybean; rhizobia; regional; templates; oilseed legumes; Nitrogen fixation; legumes; pulses; global estimates
• ISSN: 0032-079X; 1573-5036; 1573-5036
• DOI: 10.1007/s11104-021-05166-7

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 oilseed 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.