Comparison between traditional and soilless culture systems to produce rocket (Eruca sativa) with low nitrate content

Rocket is traditionally cultivated in soil and commercialized either as fresh or as ready-to-eat produce. This leafy vegetable is often commercialized fresh, cut, washed, conditioned in packages as ready-to-eat food, giving added-value to the fresh products. Soilless culture system (SCS) allows to control growth factors and clean leaf production, casing and shortening postharvest handling in process industries. A comparison between the traditional culture system (TICS) and a SCS was effected, with two plant densities (1067 and 2134 plants/m(2)). TCS was simulated in polystyrene trays filled with local soil and peat (1:1 v/v), overhead irrigation and weekly fertilization. For SCS 40-cell trays were filled with 1:1 perlite and peat, seeded and floated in a nutrient solution during plant growth. Fresh leaf production was significantly influenced by culture system x plant density. Rocket grown with SCS produced about 75% more than plants grown with TCS. The plants grown in SCS with the highest plant density gave the greatest production (2182 g m(-2)). Nitrate leaf content was significantly influenced by the culture systems. The leaves of plants grown with TCS contained less NO3- than those grown with SCS, in a ratio of 1:1.6 With both culture systems the nitrate content was much lower than 2500 mg kg(-1) f.w., which is the maximum content allowed by EU regulation for lettuce. In this experiment SCS allowed to enhance earliness: in fact, SCS produced marketable and ready-to-eat rocket in 70 days, while TCS would require extended growing period.