Table 7.
Estimates of annual inputs of BNF (Tg N) by symbiotic and non-symbiotic diazotrophs in cereal-based cropping systems and the year(s) for which the values were calculated.
| Crop system | Diazotroph | Smil (1999) | Herridge et al. (2008) | Ladha et al. (2016) | Battye et al. (2017) | Herridge et al. (2022) |
|---|---|---|---|---|---|---|
| 1994–96 | 2005 | 2010 | 2013 | 2018 | ||
| Grain legumes | Rhizobium-legume symbiosis | 10 (8–12) | 21.5a | 32.5b | 35.5c | |
| Rice cultivation | free-living, endophytic and/or symbiotic (Azolla) | 5 (4–6) | 5 | 5.6d | 10 | |
| Cereals other than rice Cereals including rice |
free-living, endophytic | 4 (2–6) | < 4 | 9.2e |
a
Soybean 16.4 and other legumes 5.1 Tg N.
b
Soybean 25 and other legumes 7.5 Tg N.
c
Soybean 25.0 and other legumes 10.5 Tg N.
d
Updated value for 2018 calculated to be: 6.9 Tg N.
e
Maize 5.9 and wheat 3.3 Tg N in 2010; updated values for 2018 calculated to be: maize 5.7 and wheat 3.1 Tg N.