The study was carried out at Zonal Agricultural Research Station (ZARS) Brahmavar, Udupi district. To know the effect of Calcium, Magnesium (Mg) and Boron (B) on yield and yield components of rice and also their residual effect on groundnut. The geographical position of the area is between 74º45’ to 74º46' East longitude and 13º24'45’’ to 13º25’30’’ North latitude and is at an altitude of 10 meters above mean sea level. Field experiments were established using three levels of Ca (0, 400 & 800 kg ha_1), two levels of Mg  (0 & 120 kg ha_1) and foliar spray of boron at two levels (0 & 0.5 %) combined to give 12 treatments. Groundnut crop was grown as a residual crop in the same plots in which rice has been raised in the previous season, for this recommended dose of fertilizer was applied along with that borax was sprayed on the 45th day after sowing. Results showed that the different combinations of Ca-Mg-B significantly influenced the yield and yield components of rice. The highest were recorded from Ca, Mg and B at 800 kg, 120 kg and 550 g ha-1 respectively. The lowest was recorded in control plot (Ca0-Mg0-B0). In case of groundnut the highest was found from Ca, Mg and B at 800 kg, 120 kg and 550 g ha-1 respectively this treatment was limed in previously cultivated rice crop and the lowest was recorded from control plot.