The importance of accounting method and sampling depth to estimate changes in soil carbon stocks

Table 4 T-test results with confidence intervals for the difference between Century wheat ESM and FD mean stock change estimates

Treatment^b	ESM depth (cm)	Difference in mean between ESM and FD stock change^a (Mg C ha ⁻¹)	95% CI for difference in mean between ESM and FD stock change (Mg C ha ⁻¹)	t-statistic	Hedges’ g effect size	p-value
IW	0–15	2.23	−0.45, 4.90	1.87	1.00	0.093
	15–30	1.50	−1.94, 4.94	0.97	0.52	0.353
	30–60	−1.06	−5.05, 2.93	−0.60	−0.32	0.565
	60–100	−0.12	−4.29, 4.06	−0.06	−0.03	0.950
	100–200	−2.90	−24.19, 18.40	−0.31	−0.16	0.766
IW + N	0–15	3.55	1.35, 5.76	3.65	1.95	0.005
	15–30	0.66	−3.90, 5.21	0.33	0.17	0.752
	30–60	−2.50	−9.32, 4.32	−0.82	−0.44	0.433
	60–100	−0.66	−12.84, 11.53	−0.12	−0.06	0.907
	100–200	−1.47	−20.70, 17.75	−0.17	−0.09	0.868
RW	0–15	3.14	0.91, 5.38	3.21	1.71	0.011
	15–30	0.36	−2.13, 2.85	0.32	0.17	0.755
	30–60	−2.10	−4.92, 0.72	−1.66	−0.88	0.128
	60–100	−1.03	−5.33, 3.27	−0.54	−0.29	0.602
	100–200	−1.00	−7.00, 5.00	−0.37	−0.20	0.718
RW + N	0–15	3.95	1.49, 6.40	3.68	1.96	0.006
	15–30	−0.45	−3.04, 2.13	−0.40	−0.21	0.700
	30–60	−1.96	−7.71, 3.80	−0.79	−0.42	0.452
	60–100	−0.41	−9.51, 8.68	−0.10	−0.05	0.921
	100–200	1.64	−14.49, 17.78	0.23	0.12	0.824
RW + WCC	0–15	3.93	1.05, 6.81	3.04	1.62	0.013
	15–30	0.34	−3.30, 3.97	0.22	0.12	0.833
	30–60	−2.33	−6.65, 2.00	−1.25	−0.67	0.248
	60–100	0.33	−4.08, 4.74	0.17	0.09	0.871
	100–200	−3.00	−11.06, 5.06	−0.83	−0.44	0.426

^aThe difference in mean between ESM and FD is calculated as ESM-FD. Under the assumption that the stock change estimated by ESM is correct (see Methods), the difference between ESM and FD can be regarded as the error from FD
^bTreatment abbreviations are as follows: IW is irrigated wheat-fallow; IW + N is irrigated wheat fallow with fertilizer; RW is rainfed wheat-fallow; RW + N is rainfed wheat-fallow with fertilizer; RW + WCC is rainfed wheat with cover crops after wheat harvest and summer fallow

ISSN: 1750-0680