Tóth, T., M. Kertész and L. Pásztor 2000. Method for the application of gypsum 
to sodic soils using GIS. (Hung.) Agrokémia és Talajtan. 49:55-64

Based on the analysis of a plot of the Trans-Tisza region of Nagykunság 
(Hungary) which have sodicity in a mosaic-like manner we proved that the 
gypsuming can be rationalized considerably be the use of aerial photo.
The reflectance of the patches on the aerial photo is proportional to the gypsum 
requirement. Considering the reflectance of the patches inside the plot, 
reflectance-strata can be delineated for the sampling and gypsuming, either 
digitally (with GIS) or intuitively on the printout. The linear relationship 
between the reflectance and gypsum requirement can be utilized to test 
alternative sampling and gypsuming plans in GIS and therefore optimize the 
reclamation.