Effects of 24 Years of Conservation Tillage Systems on Soil Organic Carbon and Soil Productivity

Table 5

Paired comparisons using MP as baseline to determine no-till (NT) and chisel plow (CP) effects after 24 years of tillage treatments on the volumetric SOC content change of the Grantsburg soil.

Tillage treatment	Depth; cm	June 2012	Comparison method NT or CP versus MP 24 yr total SOC retained above MP	Paired comparison annual SOC retention rate above MP the comparison baseline
			Mg C ha^−1layer^−1
	0–15	26.3a**	+7.5	+0.31
NT	15–75	24.6a	+0.3	+0.01
	0–75 (all)	50.9a	+7.8	+0.32
	0–15	20.3b**	+1.5	+0.06
CP	15–75	21.7a	−2.6	−0.11
	0–75 (all)	42.0b	−1.1	−0.05
	0–15	18.8b
MP	15–75	24.3a
	0–75 (all)	43.1b

**Means six replications with the same letter and in the same year and depth with a different tillage treatment are not significantly different at 𝑃=0.05.