Ways of reducing rocket salad nitrate content

Grouped under the name of rocket salad a number of species of the Brassicaceae family belong to the Eruca Miller and Diplotaxis DC genera. The popularity of rocket as a leafy vegetable is because of the spicy hot taste of its leaves which are used as garnish salads, snacks, and a large variety of meals. Rocket has a short production cycle and can accumulate large amounts of nitrate in leaves (up to 10 g/kg fresh weight), a compound believed to be potentially toxic to human health. This paper reports on a number of soilless trials carried out on rocket salad to evaluate the effect of species, light, temperature, N level (1, 4, and 8 mM), N form ratio (NH4+:NO3-= 100:0, 50:50, and 0:100), and withdrawal of N some days before harvest on nitrate accumulation and yield. In order to reduce NO3- in rocket without affecting yield the following conclusions are made: 1) remove part of leaf petioles; 2) remove part or all of the nitrate nitrogen from the nutrient solution a few days before harvesting; 3) use nutrient solutions with NO3-N and NH4-N rather than nitrate nitrogen only