Group | Criteriona | Low susceptibility to biasb | High Susceptibility to Bias |
---|---|---|---|
Study design | Study type | Before-After Control-Impact and Randomized Controlled Trials (though we do not expect to find RCTs as they are uncommon in this field) | Control-Impact study designs (no pre-impact data) |
Experimental randomizationc | Suitable experimental designs for randomization (e.g., completely randomized, randomized complete block, Latin square, factorial, split-plot, strip-plot) | Purposive (selective) | |
Experimental replication (spatial) | Replication at level of intervention (i.e., spatial replication) and of large sample size (3 +) | Replication at level of intervention but of low sample size (< 3) | |
Similar starting point | Experimental treatment and control groups are similar at the start of the trial | Experimental treatment and control groups are not similar at the start of the trial | |
Randomization | Some degree of randomization in sample selection | No randomization (i.e., purposive sampling) | |
Replication of sampling | Replication of samples (3+) | Low replication (< 3) | |
Study measurement and data analysis methods | Time between intervention (i.e., last amendment/biosolids application and soil measurement sampling) | At least 1 year since last application | < 1 year since last application |
Soil organic carbon/matter measurement method and details | Uses dry combustion/elemental analysis or Walkley–Black titration method to measure soil organic carbon/matter. Uses and details acid treatment to remove inorganic carbonates, if necessary | Uses loss-on-ignition or other method to measure soil organic carbon/matter or missing methodological detail to determine soil organic carbon/matter | |
Soil measurement depth (if incorporated or injected in soil subsurface) | Soil measured to at least depth of biosolids incorporation/injection | Soil not measured to depth of biosolids incorporation/injection or does not include details to determine depth measured | |
Soil bulk density measured | Soil bulk density measured | Soil bulk density not measured | |
Incomplete/Missing outcome data | No missing data; reasons for missing data not related to outcome; missing data balanced across control and intervention groups (and reasons similar); or proportion missing/plausible effect size not enough to have a relevant effect | Reasons related to outcome, and imbalance in numbers or reasons; or proportion missing/plausible effect size enough to have a relevant effect | |
Account for confounding variables | Presence of confounders | No obvious confounders or adequately accounted for as a result of blocking/pairing | Confounders present and/or unaccounted for (e.g., different irrigation strategies with no blocking of added treatment effect) |