Improving soil organic carbon mapping in farmlands using machine learning models and complex cropping system information

Environmental Sciences Europe

Table 1 Influencing factors of SOC

Category	Environment variable	Resolution/scale	Source
Soil properties	Soil types	250 m	Soil grids
	Clay content	250 m	Soil grids
	Silt content	250 m	Soil grids
	pH	250 m	Soil grids
	Total nitrogen, TN	90 m	National Earth System Science Data Center
	Total phosphorus, TP	90 m	National Earth System Science Data Center
	Total potassium, TK	90 m	National Earth System Science Data Center
Climate	Mean annual temperature, MAT	30 m	Chengdu Institute of Mountain Hazards and Environment, Chinese Academy of Sciences
Climate	Mean annual precipitation, MAP	30 m	Chengdu Institute of Mountain Hazards and Environment, Chinese Academy of Sciences
Organism	Annual NDVI maximum, NDVImax	30 m	Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences
Organism	Annual NDVI average, NDVImean	1 km	Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences
Spatial position	Administrative district (AD) Distance from the nearest irrigated canal Distance from the nearest rural settlement		Based on the boundaries of county-level administrative districts Based on land use map
Spatial position	Distance from the nearest pond Distance from the nearest river