Response of Radish to Phosphorus and Potassium Fertilization on Histosols

Five field experiments were conducted from 1986 through 1988 to evaluate the response of radish (Raphanus sativus L.) to rate and source of P (triple super- phosphate and phosphoric acid) and to rate of K (KC1) on Histosols. Marketable radish root yields increased with P fertilization when the soil tested <13 mg P/dm 3 using a test for water-soluble P. No significant differences were due to P source. Results of leaf tissue analysis suggested that the critical concentration of P in radish leaves was 0.45%. Radish did not respond to K fertilization in any of the five experiments, even though preliminary soil-test K levels ranged from 20 to 102 K/dm 3 . Histosols used for crop production in Florida rarely test below 20 mg K/dm 3 ; thus, radish rarely would require supplementary K fertilization for optimal yield.