In order to develop a scientific base for prescribing fertilizer recommendations for carrot, the field trial was conducted at the field in the Horticultural Research Station, located in Nilgris district, Tamil Nadu, India. The soil test calibration for fertilizer prescription based on the concept of yield targeting of carrot provides a means for the computation of critical soil test values. These values are the soil test levels above which there would be no requirement of fertilizer application for indicated levels of crop yield (Randhawa and Velayudham, 1982). Hence in the present study, an attempt was made to fix the critical soil test values for KMnO4-N, Bray-P and NH4OAc-K. For 400 q ha-1 yield target, the critical level of NPK was 1130, 379 and 830 kg ha-1 under NPK alone; 914, 358 and 756 kg ha-1 for NPK with SheepManure(SM) and 844, 358 and 756 kg ha-1 for NPK with SM plus Azospirillum respectively. Likewise the critical levels of NPK for 500 and 600qha-1 were computed. The findings of the present study revealed that the critical soil test values for KMnO4-N, Bray-P and NH4OAc-K were low under IPNS treatments (NPK plus SM and NPK with SM plus Azospirillum) as compared to NPK alone. This in turn resulted in saving of NPK fertilizers. Irrespective of treatments, higher yield targeting resulted in higher critical levels of nutrients in the soil. The results showed that IPNS resulted in low critical soil test values over NPK alone.