We are classifying the soil fertility for the delta, for which we need updates or modifications of the system developed by Sanchez et al (2003) from around countries.
In India, land capability classification has been done. But I am sure there is so soil fertility capability classification system for the entire country. However you may refer to: Adhikari 2010 and Bera 2014 (files Attached) for regional assessment study.
It is suggested for use of the technique, soil-test crop response based application of fertilizers and manures for sustainable crop production system. Further, it is also required to control the soil acidity, or alkalinity or degradation through use of suitable soil amendments. I think, this approach would serve the purpose for soil fertility capability classification.