Table 7: Use of pretillage treatment (1988) SOC values (sod) as baseline to determine the total SOC change in the first 12 years and during 24 years of tillage treatments. The 2000 SOC values for each plot were used as baseline to determine the total SOC content change during the last 12 years for the Grantsburg soil.

Tillage treatment (6 replications) Depth cmFirst 12-yr tillage effect on SOC total change by treatment using 1988 baselineLast 12-yr tillage effect on SOC total change by treatment using 2000 baseline24 year tillage effect on SOC total change by treatment using 1988 baseline
Mg C ha−1 layer−1 (% change)

0–15−1.7 (−6)−0.5 (−2)−2.2 (−8)
NT 15–75−3.4 (−14)+4.4 (+22)+1.0 (+4)
0–75 (all)−5.1 (−10)+3.9 (+8)−1.2 (−2)

0–15−3.4 (−12)−4.7 (−19)−8.1 (−28)
CP15–75−4.8 (−20)+3.0 (+16)−1.8 (−8)
0–75 (all)−8.2 (−16)−1.7 (−4)−9.9 (−19)

0–15−8.3 (−29)−1.1 (−5)−9.5 (−34)
MP15–75−5.3 (−23)+6.5 (+36)+1.2 (+5)
0–75 (all)−13.6 (−27)+5.5 (+14)−8.2 (−16)