Table 6 Variations in the soil organic carbon (SOC) content (g kg-1) during 21 years of study as influenced by tillage, straw, and fertilizer management practices (standard deviation from the mean) (At the conclusion of the experiment in 2021).

4.7 ± 0.26

2.6 ± 0.12^b

3.1 ± 0.19^b

3.9 ± 0.18^b

5.4 ± 0.26^a

5.8 ± 0.28^a

3.0 ± 0.17^b

3.7 ± 0.19^b‡

4.5 ± 0.25

2.0 ± 0.09^b

2.7 ± 0.12^b

3.2 ± 0.17^a

5.2 ± 0.22^a

5.5 ± 0.23^a

2.5 ± 0.11^b

3.1 ± 0.18^c

3.1 ± 0.19

1.8 ± 0.10^ab

2.3 ± 0.15^ab

2.4 ± 0.13^a

4.5 ± 0.19^b

5.1 ± 0.21^b

2.1 ± 0.13^ab

2.1 ± 0.13^d

2.3 ± 0.13

0.9 ± 0.05^b

1.2 ± 0.12^b

1.9 ± 0.11^a

2.7 ± 0.15^a

3.4 ± 0.19^c

1.1 ± 0.10^b

1.1 ± 0.07^b

1.4 ± 0.09

0.69 ± 0.04^c

0.93 ± 0.06^c

1.1 ± 0.07^b

1.9 ± 0.12^b

2.3 ± 0.13^d

0.87 ± 0.06^c

0.9 ± 0.05^c

3.2 ± 0.18

1.6 ± 0.08^b

2.1 ± 0.13^ab

2.5 ± 0.13^b

3.9 ± 0.19 ^b

4.4 ± 0.21^a

1.9 ± 0.11^b

2.2 ± 0.12^c

4.7 ± 0.26

4.8 ± 0.23^b

4.9 ± 0.23^a

2.9 ± 0.16^b

3.4 ± 0.22^b

4.4 ± 0.24^ab

5.1 ± 0.21^b

2.7 ± 0.14^b

4.5 ± 0.25

3.3 ± 0.18^c

4.1 ± 0.21^b

2.4 ± 0.11^b

2.9 ± 0.14^b

3.1 ± 0.12^bc

4.6 ± 0.19^b

2.2 ± 0.10^b

3.1 ± 0.19

2.8 ± 0.15^c

3.1 ± 0.18^c

2.1 ± 0.12^ab

2.4 ± 0.18^ab

2.6 ± 0.11^c

3.3 ± 0.18^c

2.0 ± 0.11^ab

2.3 ± 0.13

1.9 ± 0.11^a

2.3 ± 0.14^a

1.0 ± 0.08^b

1.3 ± 0.16^b

1.5 ± 0.10^b

2.8 ± 015^d

1.0 ± 0.06^b

1.4 ± 0.09

1.2 ± 0.07^b

1.5 ± 0.09^b

0.82 ± 0.05^c

0.98 ± 0.06^c

1.1 ± 0.0.09^cd

1.6 ± 0.10^b

0.78 ± 0.05^c

3.2 ± 0.18

2.8 ± 015^c

3.2 ± 0.17^c

1.8 ± 0.10^b

2.2 ± 0.15^b

2.5 ± 0.17^c

3.5 ± 0.18^b

1.7 ± 0.09^b