The Effects of Nitrogen Fertilization on Glucosinolate Concentration and Yield in 28 Cabbage Varieties

Cabbage, Brassica olerecea var. Capitata, is a significant vegetable crop in North Carolina with approximately 5000 acres harvested annually and an estimated market value of 15 million dollars.  This is partly driven by increased interest by consumers in the health and phytonutrient quality of this crop.  Members of the Brassicaceae family produce glucosinolates, which have been shown to have anti-cancer properties. These compounds play a role in both flavor development and influence the crops insect susceptibility.  The purpose of this study was to evaluate established varieties and elite breeding germplasm in the field, with an emphasis on the impact of nitrogen fertilization and growing season influence on both production and the concentration of glucosinolates present.  Eleven commercially available cultivars and 17 elite selections from the North Carolina State University Plants for Human Health germplasm collection were planted at the Piedmont Research Station in Salisbury, NC, in a replicated field trial.  The trial was conducted over two growing seasons, spring and fall, at the same location.  Three nitrogen levels were imposed based on the recommended rate for cabbage in North Carolina.  Heads were harvested by hand based on days to maturity and head firmness. Significant differences in yield across nitrogen treatment and genotype were observed.  Top performing varieties included Checkmate, SVR5210207, SVR05291201, C28xC519, and Platinum Dynasty.  Differences among varieties exist within nitrogen treatments.  Postharvest phytonutrient analysis was completed at the North Carolina Research Campus’s Plants for Human Health Institute in Kannapolis, NC, using HPLC-MS. While total glucosinolate concentration decreased with increasing N, indole glucosinolates were affected most by N treatment.