Enhancing sustainability in kohlrabi production by balancing nitrogen use without compromising inner and outer quality aspects

Sustainability of vegetable production is a declared goal for a more sustainable agriculture in the future. Nitrogen is a crucial macro- nutrient for achieving high yields and quality such as intense greenness in vegetables, particularly in leafy varieties. However, excessive nitrogen contributes to greenness but can lead to groundwater pollution through nitrate leaching. This study evaluates a strategy to enhance the sustainability of kohlrabi production (Brassica oleracea) by reducing N application while improving N use efficiency. It further investigates how product quality such as glucosinolate concentration is affected under these conditions. By applying 80% and 50% of the nitrogen fertilizers which contain an urease inhibitor or an additional nitrification inhibitor, higher sustainability through the mitigation of nitrogen losses is expected. The results show that a 20% reduction in N application is feasible with minimal yield loss and no significant effects on crop vitality or leaf greenness. The type of fertilizer had little impact on yield when 80% of N was supplied. While a 20% N reduction influences glucosinolate profiles, the effect on taste and quality, remains unclear. Overall, a 20% reduction in nitrogen fertilization can be accomplished without yield loss or significant changes in outer quality, although it may slightly alter glucosinolate profiles and taste perception.