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

Table 5 T-test results with confidence intervals for the difference between WICST 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
Maize	0–15	−2.17	−10.15, 5.81	−0.56	−0.22	0.579
	15–30	−0.18	−8.26, 7.90	−0.05	−0.02	0.964
	30–60	1.79	−10.59, 14.17	0.30	0.12	0.767
	60–90	0.75	−19.90, 21.39	0.07	0.03	0.941
MS	0–15	−6.98	−12.98, -0.98	−2.37	−0.77	0.024
	15–30	0.22	−9.11, 9.55	0.05	0.02	0.962
	30–60	4.72	−12.40, 21.84	0.56	0.18	0.579
	60–90	−0.86	−6.90, 5.18	−0.29	−0.10	0.773
MSW	0–15	−3.55	−8.03, 0.94	−1.58	−0.38	0.119
	15–30	−0.33	−5.92, 5.25	−0.12	−0.03	0.905
	30–60	2.54	−10.84, 15.92	0.38	0.09	0.705
	60–90	0.09	−2.90, 3.08	0.06	0.01	0.953
MAAA	0–15	−1.51	−4.83, 1.82	−0.90	−0.20	0.370
	15–30	0.74	−4.75, 6.23	0.27	0.06	0.790
	30–60	0.70	−12.06, 13.47	0.11	0.02	0.913
	60–90	−0.48	−4.62, 3.66	−0.23	−0.05	0.818
MOA	0–15	−2.34	−7.90, 3.22	−0.84	−0.23	0.403
	15–30	1.55	−5.50, 8.60	0.44	0.12	0.661
	30–60	0.63	−7.73, 8.99	0.15	0.04	0.881
	60–90	−1.97	−14.28, 10.33	−0.32	−0.09	0.749

^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: Maize is continuous maize with high external inputs; MS is moderate external input, no-till maize-soybean; MSW is organic maize-soybean-wheat followed by cover crop; MAAA is maize-alfalfa-alfalfa-alfalfa rotation; MOA is organic maize-oats/alfalfa/alfalfa rotation

ISSN: 1750-0680