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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






Study ID

First author

Mainly last name of the first author

Publication year

Year the article is published


Code for each data point in the study


Name of research group

Research group

Listing the research group that implemented the research and experiment


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


Type of paper


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


Study location

Study area

The area where the study has been conducted

Longitude and latitude

The longitude and the latitude of study area


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


Experimental 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


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


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


Ecosystem services (ESS)


List of ESS measured in the study

Measurement unit

Unit used to measure ESS


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