Add to ORKGNot AvailablePRESENTS RESULTS OF A TRIAL ON THREE LEVELS OF NITROGEN (0, 20 AND 60 kg/ha ) IN COMBINATION WITH THREE LEVELS OF PHOSPHOROUS (0,20 AND 40 kg/ha) CONDUCTED IN A RANDOMISED BLOCK DESIGN WITH THREE REPLICATIONS SEPARATELY ON TWO DIFFERENT VARIETIES ( PL- 56 AND P- 133) OF RAINFED BARLEY CROP AT SELAKUI. THE QUADRATIC RESPONSE SURFACE EQUATION WAS COMPUTED FOR THE AVERAGE YIELD OF FOUR YEARS SEPARATELY ON THE TWO VARIETIES (PL- 56 AND P-133) OF RAINFED BARLEY CROP FOR DESCRIBING YIELD - FERTILIZER RELATIONSHIP. WITH THE HELP OF THESE FITTED RESPONSE SURFACE EQUATIONS OPTIMUM DOSES OF NITROGEN AND PHOSPHOROUS WERE ESTIMATED . MARGINAL PRODUCTS , YIELD ISOQUANTS, MARGINAL RATE OF SUBSTITUTION AND LEAST COST COMBINATION WERE AL...