Field experiments with graded levels of N, P and K fertilizers were conducted in mature rubber, clone RRII 105, in farmers field in six locations of Kerala representing the major soil series, viz. Kanjirappally, Thiruvanchoor, Kadamband and Kunnathur. The treatments were N, P2O5 and K2O @ 18:18:18, 36:36:36 and 54:54:54, standard general fertilizer recommendation (GFR) of 30:30:30 kgha-1, soil test based fertilizer recommendation (DFR) and “a no” fertilizer control. The yield data showed no statistical difference among the treatments in the four locations where the soil was either Kanjirappally or Thiruvanchoor series. However, significant response to higher levels of fertilizer was observed in Kadambanad and Kunnathur series having high gravel content, indicating that fertilizer response in rubber is related to the soil properties and the capacity of the soil to supply the nutrients.