Soil Fertility Constraints
Prevalence of Low Nutrient Capital Reserves (k): Sub-Saharan Africa
Source: Ahamed et al 2006.
HarvestChoice deals with two types of soil fertility data as they relate to the productivity of agricultural systems. The first are the databases of individual soil properties, often provided at multiple depths, e.g. top-soil and sub-soil values for each property. Selected sets of these properties are used with relatively minor modification as direct input into crop growth models
. Within the crop growth models these data condition the dynamic and location-specific assessment of soil water holding capacity and soil nutrient stocks and flows, and hence crop growth potential, based on mathematical relationships that reflect our understanding of the biophysical processes involved.
Here we describe other aggregated indicators of soil fertility that provide a more strategic overview of likely favourable and unfavourable conditions for crop growth as well as of the nature of the specific constraints involved. HarvestChoice makes extensive use of the Fertility Capability Classification (FCC) approach, initially developed by Sanchez et al (1982) that has been periodically updated (FCC Ver. 4, Sanchez et al. 2003) and re-applied (Ahamed et al. 2006). HarvestChoice scientists have been involved in these continuing efforts, including the most recent global assessment of the prevalence of 17 FCC indicators
based on an interpretation of the FAO Digital Soil Map of the World
(Ahamed et al 2006). HarvestChoice is now working with the Tropical Agriculture Program of the Earth Institute at Columbia University to re-apply the FCC Ver. 4 methodology to the new Harmonized Soil Map of the World.
Extent of Soil Fertility Constraints (FCC Indicators) for Tropical Soils
Soil Functional Capacity (FCC code) |
Prevalence in Tropical Soils |
|
|
( %) |
(M has) |
Seasonal soil moisture stress d |
43.6 |
2154.9 |
Aridic d+ |
25.8 |
1272.7 |
High soil erosion risk y |
10.9 |
539.7 |
Low nutrient capital reserves k |
36.5 |
1803.5 |
Calcareous b |
6.9 |
342.4 |
Permafrost t+ |
0.3 |
12.7 |
Aluminum toxic a |
27.8 |
1374.6 |
Cold t |
0.4 |
20.9 |
Waterlogged g |
8.5 |
419.0 |
High P fixation i |
10.5 |
519.8 |
High leaching potential e |
9.0 |
443.2 |
High organic content O |
0.9 |
44.6 |
Cracking clays v |
4.5 |
220.2 |
Sodic n |
1.7 |
81.3 |
Saline s |
0.7 |
35.3 |
Volcanic x |
0.5 |
24.2 |
Sulfidic c |
0.3 |
12.5 |
Note: Percentages sum to greater than 100% because of multiple constraints associated with some soil types.
Source: Ahamed et al 2006.
References
Sanchez, P.A., W. Couto, and S.W.Buol. 1982. The Fertility Capability Soil Classification System: Interpretation, Application and Modification. Geoderma. Vol 27(4): 283-309
Sanchez, P.A., C.A. Palm, and S.W.Buol. 2003. Fertility capability soil classification: a tool to help assess soil quality in the tropics. Geoderma. Vol 114: 157-185
Ahamed, S., D. Balk, R. Flor, M. Levy, C. Palm, P. Sanchez, A. Storeygard, S. Wood. Soil Functional Capacity Classification Map of the World. World Soil Science Congress, Philadelphia. July 10-14, 2006.
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JPG  | Prevalence of Low Nutrient Capital Reserves (k): Sub-Saharan Africa |
| PPT | FCC Poster: Soil Functional Capacity Classification Map of the World |
