RESIDUAL SODIUM CARBONATE (RSC)

The excess milliequivalents of carbonate and bicarbonate over the milliequivalents of calcium and magnesium in a sample of water, where: RSC = ( CO3-2 + HCO3-2 ) : ( Ca+2 + Mg+2 ); where all concentrations are expressed in milliequivalents per liter (meq/l). Waters with RSC values over 2.5 are generally not suitable for irrigation uses.