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

Table 6

Use of pretillage treatment 1988, 2000, and 2012 SOC during 24 years of tillage treatments.

Tillage treatment	Depth cm	September 1988	August 2000	June 2012
		(pretreatment baseline)	Mg C ha^−1 layer^−1
	0–15	28.5a**	26.8a**	26.3a**
NT	15–75	23.6a	20.2a	24.6a
	0–75 (all)	52.1a	47.0a	50.9a
	0–15	28.4a	25.0a	20.3b
CP	15–75	23.5a	18.7ab	21.7a
	0–75 (all)	51.9a	43.7ab	42.0b
	0–15	28.3a	19.9b	18.9b
MP	15–75	23.1a	17.8b	24.3a
	0–75 (all)	51.4a	37.7b	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.