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Table 1 The variables used for the random forest models

From: Soil carbon-food synergy: sizable contributions of small-scale farmers

Category

Variable

Unit

Dataset and source

Yield

Average yield (wheat, maize, rice, soybean, sorghum, millet)

t ha–1

M3, Monfreda et al. (2008)

SPAM2005, Wood-Sichra et al. (2016)

Soil

Topsoil (0–30 cm) organic carbon content

kg C m–2

GSOC, FAO and ITPS (2018)

mm per m of the soil unit

HWSD, Wieder et al. (2014)

Available water storage capacity

Climate

Season temperature

°C

S14FD, Iizumi et al. (2017b)

Season water balance index

mm season–1

Management

Nitrogen application rate

kg N ha–1 year–1

Mueller et al. (2012)

Pesticide application rate

kg ha–1 year–1

PEST-CHEMGRIDS, Maggi et al. (2019)

Irrigation intensity

Fraction to harvested area

MIRCA, Portmann et al. (2010)

Farm field size

Category

Fritz et al. (2015)

Agricultural knowledge stock

Billion USD

Iizumi et al. (2017a)