Table 2.

Global estimates of terrestrial denitrification.

	total	soil	groundwater	riparian zone
	N (Tg yr−1)
total
Emery et al. [22]	69
Gruber & Sarmiento [23]	175–202
Codispoti et al. [24]	255–450
Søderlund & Svensson [25]		108–160
Tiedje [2]a		105–185
Van Drecht et al. [18]; Seitzinger et al. [21]		124	44
Canfield et al. [26]	100
Galloway et al. [1]a (year ∼2000)	125
Galloway et al. [1]a (year 2050)	173
this study (year 2000)	109 (101–118)b	79 (72–85)b	24 (19–29)b	6 (5–9)b
this study (year 2050)	110–158c	80–119c	24–30c	6–8c
agriculture
Hofstra & Bouwman [26]		22–87
this study (year 2000)		51

^aAs estimates are based on mass balance considerations, these numbers probably represent total terrestrial denitrification.

^bStandard model and range from sensitivity analysis (electronic supplementary material, table S5 and S6).

^cLowest (TG) and highest (GO) scenario.