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Table 1 Critical appraisal criteria

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

Spatial (true) replication2 replicates0
 3–4 replicates1
 >4 replicates2
Temporal replication≤3 replicates0
 4–6 replicates1
 >6 replicates2
Treatment allocation (as described for the full experimental design)Purposive (selective)0
 Split-/strip-plot/latin square/blocked/randomised/exhaustive2
Duration of experiment10–19 years0
 20–29 years1
 ≥30 years2
Soil sampling depthShallow (maximum depth ≤15 cm) single or multiple sampling0
 Plough layer (maximum depth 15–25 cm) single or multiple sampling, or deep (maximum depth >25 cm) single sampling1
 Multiple deep sampling (maximum depth >25 cm)2