Table 8.

Field estimates of the inputs (kg N ha^-1 per crop) of non-symbiotic/free-living BNF in rice, wheat, and maize systems.

Location	Annual crop rotation	Crop	No. of crops	Year	Method	Input of fixed N	Remarks	Reference
Jiangdu, China	rice-rice	rice	1	N/Aa	15N2 feeding	4–19b	direct method (90 d15N2 incubation)	Zhang et al. (2021)
Jiangdu, China	rice-rice	rice	1	N/Aa	15N2 feeding	11	direct method (28 d15N2 incubation)	Wang et al. (2020)
Jiangdu, China	rice-wheat	rice	1	N/Aa	15N2 feeding	22–51	direct method (74 d15N2 incubation)	Ma et al., 2019a, Ma et al., 2019b
Jiangdu, China	rice-wheat	rice		2010	15N2 feeding	45	direct method (70 d15N2 incubation)	Bei et al. (2013)
Global average	single to multiple	rice	50	1960–2010	N balance	22	excluding deposition and seed N	Ladha et al. (2016)
Bocol, Philippines	rice-rice	rice	30	1968–83	N balance	35	excluding deposition	Pampolina et al. (2008)
Los Banos, Philippines	rice-rice	rice	30	1964–79	N balance	18	excluding deposition	Pampolina et al. (2008)
Maligaya, Philippines	rice-rice	rice	30	1968–83	N balance	44	excluding deposition	Pampolina et al. (2008)
Los Banos, Philippines	rice-rice-rice	rice	45	1963–83	N balance	27	excluding deposition	Pampolina et al. (2008)
Los Banos, Philippines	rice-rice	rice	27	1985–98	N balance	46	excluding deposition	Ladha et al. (2000)
Pakistan		rice	1	N/Aa	15N dilution	46	including deposition	Malik et al. (1997)
Global average	Rice	rice	N/A	N/Aa	N balance	30	excluding deposition	Roger and Ladha (1992)
Japan	Rice	rice	1	N/Aa	N balance	40–45	including deposition	Marumoto (1986)
Los Banos, Philippines	rice-rice	rice	24	1966–78	N balance	51	excluding deposition	App et al. (1984)
Maligaya, Philippines	rice-rice	rice	17	1968–1976	N balance	39	excluding deposition	App et al. (1984)
IARI, India		wheat	1	N/Aa	N balance	40	excluding deposition and seed N	Bageshwar et al. (2017)
Global average	single to multiple crop	wheat	50	1960–2010	N balance	13	excluding deposition and seed N	Ladha et al. (2016)
Avon, Australia	Wheat	wheat	17	1979–96	N balance	20	excluding deposition and seed N	Gupta et al. (2006)
Rothamsted, U.K.	Wheat	wheat	4	1979–83	N balance	25	excluding deposition and seed N	Powlson et al. (1986)
Rothamsted, U.K.	Wheat	wheat	115	1852–1967	N balance	25–35	excluding deposition and seed N	Jenkinson (1977)
Rio de Janerio, Brazil	Maize	maize	3	N/Aa	15N dilution	26		Alves et al. (2014)
Global average	single to multiple crop	maize	50	1960–2010	N balance	13	excluding deposition and seed N	Ladha et al. (2016)

^aNot available.

^b19.25 kg N ha^-1 reported under no-N and 2.67–3.61 kg N ha^-1 with N-fertilizer (at the rates of 125–250 kg N ha^-1).