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Table 4 Data coding

From: Biochar’s effect on the ecosystem services provided by sandy-textured and contaminated sandy soils: a systematic review protocol

# Category Variable Description
1 Study ID First author Mainly last name of the first author
Publication year Year the article is published
Numbering Code for each data point in the study
2 Name of research group Research group Listing the research group that implemented the research and experiment
3 Validity of a study Validity of a study Internal and external validity of a study that will be assessed as “low”, “moderate” or “high” risk of bias
4 Type of paper Peer-reviewed If the paper is published in a peer-reviewed journal
Gray literature If it is a publication in a website, or a dissertation/thesis, or conference summaries
5 Study location Study area The area where the study has been conducted
Longitude and latitude The longitude and the latitude of study area
Country The country where the study area is located
Type of climate Classification of climate of the country
Average precipitation Expressed in mm: Average precipitation in study area
6 Experimental condition Condition Listing if it is randomized replicates or different
Experimental design If it is based on open field, greenhouse, or lab
Design characteristics Plot area, number of plots, or pots (if it is greenhouse or lab experiment)
Experimental setup Control (without amendment, or with fertilizer or with manure), treatment (with biochar, or fertilizer + biochar, or manure + biochar)
Duration of experiment Expressed in days
Biochar application rate Expressed in t/ha
7 Biochar properties Feedstock used The feedstocks used for pyrolysis will be grouped as “woody biomass”, “manure”, “peat-based”, and “agricultural residue”
Pyrolysis temperature Expressed in the Celsius scale
Carbon rate Expressed in g per kg (g/kg) and mass percentage
8 Soil status Type of soil Type of sandy soil and contaminated soil used for the experiment
Soil sample depth The minimum and maximum soil depth at which biochar is applied; expressed in cm
Soil treatment before biochar NPK fertilizer, manure, or other treatments
Soil condition Soil is tilled or irrigated before the experiment
9 Ecosystem services (ESS) Measurement List of ESS measured in the study
Measurement unit Unit used to measure ESS
10 Changes in ecosystem services Control (without amendment, or with manure, or with fertilizer) Means, SD, correlation, OR t-value OR F-score
Treatment (with biochar only, or with manure + biochar, or fertilizer + biochar) Means, SD, correlation, OR t-value OR F-score