Soil Functional Capacity Classification Map of the World

1
Soil Functional Capacity Classification Map of
the World
Sonya Ahamed 1, Deborah Balk 1, Rafael Flor 2,
Marc Levy 1, Cheryl Palm 2, Pedro Sanchez 2, Adam
Storeygard 1 and Stanley Wood 3
Mapping the global extent of soil constraints to
crop growth can play an important role in
developing strategies for agricultural
production, environmental protection, and
sustainable development at regional and global
scales. The soil fertility capability
classification system (FCC) is a widely used
technical system for interpreting soil taxonomy
and additional soil attributes in ways directly
relevant to plant growth (Buol et al.1975). FCC4,
the most recent update of the system, identifies
eight top- and sub-soil texture types and 17
condition modifiers defined to quantitatively
delimit the soil's capacity to provide ecosystem
functions and services (Sanchez et al. 2003).
Here we present maps displaying the worldwide
prevalence of the condition modifiers seen as the
most relevant to achieving the Millennium
Development Goals. The decision rules used to
generate each map are explained in the captions.
Since the system is now interpreted beyond soil
fertility, we call it Soil Functional Capacity
Classification, while retaining the original
acronym FCC.
Waterlogged soils are defined as having an aquic
soil moisture regime, where soil horizons to a
depth of 50 cm are saturated by water. This map
shows the percentage of FAO map units containing
Histosols, Thionic Fluvisols, and all soil units
beginning or ending with 'g' (indicating they
are gleyic). In hyperthermic soil temperature
regimes, these regions are often correlated with
greater incidences of malaria.
Waterlogged soils are defined as having an aquic
soil moisture regime, where soil horizons to a
depth of 50 cm are saturated by water for part of
the year. This map shows the percentage of FAO
map units containing Histosols, Thionic
Fluvisols, and all soil units beginning or ending
with g (indicating they are gleyic). In
hyperthermic soil temperature regimes, these
regions are often correlated with greater
incidences of malaria.
Soils with low nutrient capital reserves are
defined as having less than 10 weatherable
minerals in their fine silt and sand fractions
and require different management for intensive
agriculture than soils that do not have this
modifier.
Soils having permafrost within 50 cm are frozen
throughout the year therefore no cropping is
possible. The blue-colored regions in this map
depict soils classified as hypergelic, pergelic,
or gelic in the USDA's Soil Temperature Regime
(STR) dataset. The global extent of frozen soils
has been decreasing in recent years due to rising
temperatures.
1 Center for International Earth Science
Information Network, The Earth Institute at
Columbia University, Palisades, NY, USA 2
Tropical Agriculture Program, The Earth Institute
at Columbia University, Palisades, NY, USA 3
International Food Policy Research Institute,
Washington DC, USA.
Modifiers Except in the case of d and t, or -
conditions were dropped, due to the difficulty of
mapping these distinctions with existing global
datasets. The output was converted to raster
format and maps were produced using ArcGIS.
Multiple Modifiers Through the use of
taxotransfer functions, it is possible to map the
extent of all soil units assigned two or more
modifiers without obtaining sums greater than
100 within one map unit. Fine-textured Xanthic
Ferrasols, for example, receive the modifiers a,
e, i, and k.
Land Area Affected by FCC4 Condition Modifiers
Data and Methodology The Digital Soil Map of the
World (DSMW) using the 1974 Legend provided input
spatial data for 12 of the condition modifiers
(FAO 1995). The USDAs Soil Moisture Regime and
Soil Temperature Regime datasets were used for
the four modifiers directly related to moisture
and temperature. Using the soil attribute
dataset WISE-2.1, we developed a list of soil
units meeting the physical/chemical definitions
for the DSMW-based modifiers (IFPRI/ ISRIC 2002).
Both the input from this list and the soil units
used to map an earlier version of the FCC were
considered in developing the final decision rules
for each modifier (FAO 1995). To map the
results, we generated a list of the FAO map units
containing soil units for the relevant modifiers,
along with the corresponding percent area. A map
unit with a value of 60 for the k modifier, for
example, could be 40 Orthic Acrisols and 20
Plinthic Ferrasols or, say, 60 Luvic Arenosols,
or another combination of soil units adding up to
60 (in accordance with DSMW composition rules).

References Batjes, N.H. 2002a. Soil parameter
estimates for the soil types of the world for use
in global and regional modeling (ver. 2.0). ISRIC
Report 2002/02c, International Food Policy
Research Institute (IFPRI) and International Soil
Reference and Information Centre (ISRIC),
Wageningen (with dataset). Food and Agriculture
Organization of the United Nations (FAO). 1995a.
Digital Soil Map of the World and Derived Soil
Properties. Rome FAO. Sanchez, P.A., Palm,
C.A., Buol, S.W. 2003. Fertility capability soil
classification system A tool to assess soil
quality in the tropics. Geoderma
114157-185. USDA-NRCS. 1997. Soil Climate Map
Soil Temperature Regime and Soil Moisture Regime
datasets, Soil Survey Division, World Soil
Resources, Washington, D.C.
Low Nutrient Capital Reserves From Global to
Regional
This sequence of maps (right) shows the extent of
low nutrient capital reserves for progressively
smaller regions, and illustrates how GIS can be
used to zoom in on areas of interest. Because
these maps have a resolution of roughly 9 km at
the equator, they are less well-suited for local
analysis.
Presented at the World Soil Science Congress,
Philadelphia, July 10-14, 2006