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Table 8 Summary effect estimates for meta-analyses of concentration data

From: How does tillage intensity affect soil organic carbon? A systematic review

Tillage comparison

Soil depth (cm)

Summary effect estimate (g/kg)

Standard error

z statistic

p value

Lower 95% confidence interval

Upper 95% confidence interval

Number of studies

NT–HT

0–15

2.086

0.344

6.073

< 0.001

1.413

2.760

102

15–30

− 0.298

0.286

− 1.039

0.299

− 0.859

0.264

49

> 30

− 0.371

0.261

− 1.424

0.155

− 0.882

0.134

31

NT–IT

0–15

1.179

0.334

3.537

< 0.001

0.526

1.833

95

15–30

0.273

0.289

0.944

0.345

− 0.293

0.839

45

> 30

− 0.157

0.186

− 0.845

0.398

− 0.522

0.208

20

IT–HT

0–15

1.229

0.221

5.575

< 0.001

0.797

1.662

77

15–30

− 0.890

0.198

− 4.539

< 0.001

− 1.288

− 0.511

42

> 30

− 0.261

0.209

− 1.250

0.211

− 0.671

0.148

16

  1. NT no tillage, IT intermediate intensity tillage, HT high intensity tillage (see text for explanation)