Effects of Nitrogen Fertilization and Cropping Season on the Vitamin U Concentration in Cabbage

Abstract

Vitamin U (VU) concentration in cabbages harvested in Hokkaido ranged from 7.0 - 66.2 mg kg⁻¹, and the mean was 28.9 mg kg⁻¹ (1996-1998, n=92). Among cropping seasons, the mean VU concentration in cabbages was highest in July (40.6 mg kg⁻¹), then declined gradually until October (13.2 mg kg⁻¹). VU concentration in cabbages increased with increases in applied nitrogen (N) fertilizer, or growth in fields with higher N fertility, and in summer cropping rather than autumn cropping. In the case of cabbbage production using organic matter to reduce usage of chemical fertilizer, the VU concentration in cabbage grown with fish meal (fast-N-release) was higher than that growth with rice bran (slow-N-release). These results indicate that changes in VU concentration in cabbages depend on N nutritional condition.