Yield and Nutrient Concentrations of Kohlrabi Bulbs and Leaves as Affected by Spring Transplanting Dates

Transplanting kohlrabi (Brassica oleracea var. gongylodes), a cool-season vegetable crop, in early spring may provide the opportunity for double cropping in short-season regions such as the Northeastern United States. A two-year field study evaluated the impacts of transplanting dates on yield and nutrient concentration of kohlrabi. Additionally, this study aimed to quantify the nutritional value of kohlrabi leaves. The yield of kohlrabi increased by as much as 307 kg ha⁻¹ for each day transplanting was delayed. Soil temperature increased by 2.8 °C between April 23 and May 14, resulting in the increased accumulation of Ca, Cu, Mn, and Fe in kohlrabi bulbs and Ca and Cu in leaves. The nutrient concentration in leaf and bulb were positively correlated, indicating that the two commodities can be simultaneously harvested for optimum quality. Leaf yield was not significantly different among transplanting dates. However, the number of leaves and total leaf area increased with delayed transplanting. Leaf yield and leaf area were not correlated with bulb yield, suggesting that the reductions in yield and nutrient concentrations were unrelated to photosynthetic efficiency. Although the earlier transplanting of kohlrabi may have provided opportunities for double cropping, the yield and nutrient accumulation of kohlrabi transplanted early in the spring were considerably compromised.