FCC3 - Diagnosing constraints to crop growth with a decision aid linked to a soil database

A partnership between the 
Land and Plant Nutrition Management Service and the 
University of Hawaii

FAO Scientists repeatedly provide advice and guidance on identifying major limitations in Natural Resource Planning and Management, especially in reference to crop-related limitations of broad regions of land resources. Often there are regional limitations that have major policy implications while specific recommendation details can be handled by other forms of assistance to local scientists. One framework that identifies probable crop growth and productivity limitations is the Fertility Capability Classification System (FCC).

An early version of this system was found useful for the regional assessment of crop limitations of soils and was, therefore, selected for an integrated decision-aid and database system that would provide a diagnosis of major limitations and make suggestions arising from the assignment of some 22 modifiers in 5 categories of limitations:

1. Soil texture in the root zone,
2. Water and temperature status,
3. Mineralogy of soil materials,
4. Soil pH and acidity status, and
5. Cation status of the rooting zone.

A new version of the FCC was selected to interface with the WISE (World Inventory of Soil Emission Potentials) database, which is a integration of

1. The FAO Soils database,
2. ISRIC (International Soil Reference and Information Centre), and
3. NRCS (Natural Resource Conservation Service) foreign soil database.

A revised FCC 3rd approximation algorithm was developed that was tuned to the WISE database in order to maximize use of the information it contains. A revision of the algorithm is now being planned that fully exploits the NRCS database (NASIS, National Soil Information System). Multiple alternatives were developed to ascertain whether or not or whether there was sufficient data of the quality needed to even evaluate the modifier. As many as 4 or 5 alternatives were provided for some modifiers. Missing data was tolerated with criteria that depended on the modifier -- for depth-averaged variables as much as 50% of the data could be missing while the presence of as little as 10 cm of data was sufficient for some of the highly detrimental properties. In this way missing data were handled in a manner to maximize the use of the information that was present. 

A menu-driven interface was developed that displayed all of the pedon data, a form with the intermediate worksheet calculations such as the depth-averaged values, and a recommendation form that grouped the recommendations from the 5 categories of modifier codes. The recommendations still need some review and discussion before the software is released for extensive or mission-critical use by scientists who cannot judge the results. The review and discussion are suggested because of the vastly different purposes of the recommendations and potential use by non-experts. Finally, the program includes an option to record the results of the code assignment and selected intermediate results to a general purpose database for use in linkage and display with a GIS.

For any technical information, please contact

Jose Benites
Land and Water Development Division
FAO, Viale delle Terme di Caracalla,
00100 Rome, Italy
Jose Benites@fao.org