Net ionic equilibrium in soil-plant system – A better index of soil fertility in an ultisol

The rhizosphere soil samples, the soil solution extracted from these samples at saturated moisture status and index leaf samples of fifty coconut palms in a homogeneous coconut plantation grown under an Ultisol (Vellanikkara III series), in the main campus of Kerala Agricultural University, were critically studied with respect to the nutrient status and the mutual interaction of nutrient ions, and influence of these parameters on the nut yield. Exchangeable ions extracted by 0.1 M BaCl₂ as well as the net ionic equilibrium (NIE) ratios were found to be significantly related one another and also with the yield. NIE was found to be a better index of yield.