Overall suitability = W x NAI x I x R x O x Sa x F x E xT …………………. (1)
with the following definitions,
a) Water availability (W): Rainfall data of 30 years (1975-2005) recorded by the
Meteorological Department were used for the establishment of the ‘W’ layer. Spatially interpolated,
mean annual rainfall for the entire Northeast region of Thailand was conducted with Kriging of the
station data to yield a ‘W’ spatial map. The spatial ‘W’ layer was then divided to 4 suitability classes as Fig.1 Study area defined by Mongkolsawat et al. (2009a), Charuppat and Mongkolsawat (2003), Putklang et al. (2010)and Mongkolsawat and Putklang (2010) for the crops to be evaluated.