The data originates from the Harmonized World Soil Database version 1.2 (HWSD), jointly developed by the Food and Agriculture Organization (FAO) and the International Institute for Applied Systems Analysis (IIASA). Data for China are sourced from the 1:1,000,000-scale soil data provided by the Nanjing Institute of Soil Science during the Second National Land Survey. This dataset serves as input parameters for modeling and supports research on agro-ecological zoning, food security, and climate change from an agricultural perspective. The primary soil classification system used is FAO-90.

1、Core Soil Mapping Unit Identifiers: (1)MU_GLOBAL: Unique identifier for soil mapping units in the HWSD, linked to GIS layers.

(2)MU_SOURCE1 and MU_SOURCE2: Source database identifiers for mapping units.

(3)SEQ: Sequence of soil units within composite mapping units.

(4)Soil classification systems include FAO-7 (SU_SYM74), FAO-85 (SU_SYM85), and FAO-90 (SU_SYM90).

2、Key Soil Attribute Fields:

(1)ID: Database ID

(2)MU_GLOBAL: Global soil unit identifier

(3)SU_SYMBOL: Soil mapping unit symbol

(4)SU_SYM74: FAO-74 classification

(5)SU_SYM85: FAO-85 classification

(6)SU_SYM90: FAO-90 classification

(7)SU_CODE: Soil mapping unit code

(8)SU_CODE74/SU_CODE85/SU_CODE90: Soil unit codes under respective FAO systems

(9)DRAINAGE: Drainage class (19.5)

(10)REF_DEPTH: Reference soil depth

(11)AWC_CLASS: Available water capacity class (19.5)

(12)PHASE1 (Real)/PHASE2 (String): Soil phase descriptors

(13)ROOTS (String): Depth classification to restrictive layers

(14)SWR (String): Soil water retention characteristics

(15)ADD_PROP (Real): Soil type relevance to agricultural use

(16)T_TEXTURE: Topsoil texture

(17)T_GRAVEL (Unit: % vol.): Gravel content in topsoil

(18)T_SAND/T_SILT/T_CLAY (Unit: % wt.): Sand, silt, and clay content in topsoil

(19)T_USDA_TEX (Unit: name): USDA texture classification (topsoil)

(20)T_REF_BULK (Unit: kg/dm³): Topsoil bulk density

(21)T_OC (Unit: % wt.): Topsoil organic carbon

(22)T_PH_H2O (Unit: -log(H⁺)): Topsoil pH

(23)T_CEC_CLAY/T_CEC_SOIL (Unit: cmol/kg): Cation exchange capacity (clay layer/topsoil)

(24)T_BS (Unit: %): Base saturation (topsoil)

(25)T_TEB (Unit: cmol/kg): Exchangeable bases (topsoil)

(26)T_CACO3/T_CASO4 (Unit: % wt.): Carbonate/lime and sulfate content (topsoil)

(27)T_ESP (Unit: %): Exchangeable sodium percentage (topsoil)

(28)T_ECE (Unit: dS/m): Electrical conductivity (topsoil)

 The database divides soil into two layers: topsoil (0–30 cm) and subsoil (30–100 cm). For additional attributes, refer to the documentation: HWSD1.2_documentation.pdf, The Harmonized World Soil Database (HWSD V1.2) Viewer (Chinese documentation), and HWSD.mdb.