Soil carbon stock beneath an established irrigated pasture grazed by dairy cattle

Figures & data

Table 1 Geographic position system (GPS) coordinates for soil sampling locations at the irrigated and control sites.

Irrigated site
43° 38.365′, 172° 26.616′	43° 38.354′, 172° 26.635′ 43° 38.340′, 172° 26.652′ 43° 38.333′, 172° 26.681′ 43° 38.321′, 172° 26.702′ 43° 38.310′, 172° 26.726′
43° 38.382′, 172° 26.623′	43° 38.371′, 172° 26.645′ 43° 38.359′, 172° 26.668′ 43° 38.345′, 172° 26.693′ 43° 38.337′, 172° 26.717′ 43° 38.321′, 172° 26.702′
43° 38.371′, 172° 26.645′	43° 38.398′, 172° 26.649′ 43° 38.396′, 172° 26.672′ 43° 38.394′, 172° 26.701′ 43° 38.391′, 172° 26.727′ 43° 38.389′, 172° 26.753′
Control site
43° 38.263′, 172° 27.091′	43° 38.250′, 172° 27.076′ 43° 38.238′, 172° 27.064′ 43° 38.222′, 172° 27.067′ 43° 38.211′, 172° 27.072′ 43° 38.236′, 172° 27.063′

Figure 1 The relationship between soil carbon (C) concentration and depth, portrayed as a midpoint of the sampled interval. Mean data (± SE as error bars) from the dairy farm (n = 18) have been shown as solid circles and lines and those from control site (n = 6) as open circles and dashed lines.

Table 2 Mean cumulative soil carbon (C) stock (±SE) for increasing depths at the irrigated and control sites according to volumetric and equivalent soil mass calculations. Also shown are the corresponding cumulative soil masses.

Depth (m)	0.05	0.10	0.15	0.20	0.30	0.40	0.60	0.80
Volumetric calculations (kg C m^−2)
Irrigated	2.3 ± 0.1	4.6 ± 0.1	6.4 ± 0.2	8.0 ± 0.2	10.0 ± 0.3	11.1 ± 0.4	12.2 ± 0.4	13.0 ± 0.4
Control	1.7 ± 0.1	3.2 ± 0.2	4.5 ± 0.3	5.7 ± 0.2	7.8 ± 0.6	9.7 ± 0.7	11.8 ± 1.0	12.9 ± 0.2
	*	*	*	*	*	*	ns	ns
Cumulative soil mass (kg soil m^−2)
Irrigated	53.5 ± 0.8	117.6 ± 1.3	185.3 ± 1.7	251.8 ± 2.0	390.8 ± 3.2	541.1 ± 5.2	846.8 ± 5.9	1149.7 ± 8.1
Control	36.6 ± 3.8	89.5 ± 7.7	148.7 ± 9.8	212.0 ± 12.7	356.6 ± 18.5	492.1 ± 22.9	755.2 ± 29.2	1023.7 ± 29.1
	*	*	*	*	ns	ns	*	*
Equivalent mass calculations (kg C m^−2)
Irrigated	1.6 ± 0.04	3.5 ± 0.1	5.2 ± 0.1	6.7 ± 0.2	9.1 ± 0.3	10.1 ± 0.3	10.9 ± 0.4	11.6 ± 0.4
Control	1.7 ± 0.1	3.2 ± 0.2	4.5 ± 0.3	5.7 ± 0.2	7.8 ± 0.6	9.7 ± 0.7	11.8 ± 1.0	12.9 ± 0.2
	ns	ns	ns	*	ns	ns	ns	ns

Site differences have been denoted by * when statistically significant (P < 0.05) and ns (not significant) when not.