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

Table 3 T-test results with confidence intervals for the difference between Century maize 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
CMT	0–15	4.18	1.82, 6.54	3.95	2.11	0.003
	15–30	1.38	−2.95, 5.72	0.76	0.41	0.472
	30–60	0.17	−6.45, 6.80	0.06	0.03	0.954
	60–100	−0.85	−5.49, 3.80	−0.41	−0.22	0.694
	100–200	−2.99	−10.85, 4.87	−0.87	−0.46	0.409
CMT + WCC	0–15	4.07	1.58, 6.56	3.87	2.06	0.006
	15–30	2.37	−1.76, 6.49	1.32	0.70	0.223
	30–60	1.30	−2.40, 5.00	0.79	0.42	0.451
	60–100	−1.93	−8.02, 4.17	−0.71	−0.38	0.494
	100–200	−3.47	−19.67, 12.74	−0.48	−0.26	0.642
OMT	0–15	4.59	0.66, 8.52	2.95	1.57	0.030
	15–30	2.39	−0.13, 4.90	2.13	1.14	0.060
	30–60	−2.16	−5.54, 1.22	−1.44	−0.77	0.183
	60–100	−1.13	−5.91, 3.64	−0.53	−0.28	0.606
	100–200	−2.34	−16.00, 11.31	−0.39	−0.21	0.708

^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: CMT is conventional maize-tomato; CMT + WCC is maize-tomato with cover crop; OMT is organic maize-tomato with cover crop

ISSN: 1750-0680