Pungency Levels of Red Radish Roots Are Unaffected by Compost Treatments Used for Field Production

Field experiments were conducted at Bixby, Oklahoma in 2007.  Four compost treatments and an unamended control were compared for field production of eight (spring) or four (fall) red radish (Raphanus sativus L.) cultivars.  Treatments were either spent mushroom substrate or yard waste compost spread over plots to an average depth of 2.5 or 5 cm and preplant-incorporated.  Radishes were direct seeded into prepared plots and subsequently grown using standard cultural practices.  Harvested roots were evaluated for yield and marketability.  Samples of median-sized marketable roots were shredded and juice was analyzed in the laboratory for content of the major pungency compound, 4-methylthio-3-butenyl isothiocyanate (MTBITC).  In the spring, mean concentrations of MTBITC ranged from 15 to 19 µmol per 100 g juice in roots from the four compost treatments, and differences were not significant (α = 0.05).  There were not enough roots to analyze from the unamended control plots due to herbicide toxicity.  Cultivars differed in mean concentration of MTBITC, ranging from a high of 28 µmol per 100 g juice for ‘Cherry Belle’ to a low of 10 µmol per 100 g juice for ‘Crunchy Royale’.  In the fall, mean concentrations of MTBITC ranged from 4 to 10 µmol per 100 g juice in roots from the four compost treatments.  Differences were not significant (α = 0.05), and there were no differences from the control value of 7 µmol per 100 g juice.  The mean concentration of MTBITC was 8 µmol per 100 g juice for the four cultivars tested in the fall, and the cultivars did not differ.  Results indicate that the tested compost treatments did not affect pungency of red radish roots.