Sodium-Absorption ratio (SAR) is defined as
1
SAR = Mg++/ \(\left\{ {\sqrt {\left( {{\rm{C}}{{\rm{a}}^{{\rm{ + + }}}}\,{\rm{ + }}\,{\rm{N}}{{\rm{a}}^{{\rm{ + + }}}}} \right)} {\rm{/2}}} \right\}\)
2
SAR = Na+/ \(\left\{ {\sqrt {\left( {{\rm{C}}{{\rm{a}}^{{\rm{ + + }}}}\,{\rm{ + }}\,{\rm{M}}{{\rm{g}}^{{\rm{ + + }}}}} \right)} {\rm{/2}}} \right\}\)
3
SAR = Ca+/ \(\left\{ {\sqrt {\left( {{\rm{N}}{{\rm{a}}^{{\rm{ + + }}}}\,{\rm{ + }}\,{\rm{M}}{{\rm{g}}^{{\rm{ + + }}}}} \right)} {\rm{/2}}} \right\}\)
4
SAR = Na+/ \(\left\{ {\sqrt {\left( {{\rm{C}}{{\rm{a}}^{{\rm{ + + }}}}\,{\rm{ - }}\,\,{\rm{M}}{{\rm{g}}^{{\rm{ + + }}}}} \right)} {\rm{/2}}} \right\}\)