Comparison Between Traditional and Soilless Culture Systems to Produce Rocket (Eruca Sativa) With Low Nitrate Content

Abstract

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, easing and shortening postharvest handling in process industries. A comparison between the traditional culture system (TCS) 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 40cell 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 NO 3 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.

Yield and Quality of Lettuce and Rocket Grown in Floating Culture System

“…Cultivation system affects significantly yield and earliness (date of harvest) of leafy vegetables. Nicola et al (2005) and Fontana and Nicola (2009) compared cultivation of rocket and lettuce plants in soil and soilless media (floating systems and soil substrates) and reported higher yield and early maturity for floating system culture comparing to conventional soil culture. Higher yield in floating systems could be attributed to higher N content and availability in nutrient solution, which resulted in increased photosynthetic rate and consequently in increased fresh and dry weight of aerial parts of lettuce and rocket plants.…”

“…Therefore, the amount of applied N during cultivation should be controlled in order to avoid excessive nitrate content within plant tissues. High nitrate content in plant tissues could be attributed to high nutrient uptake from plants when grown in soilless cultures (Rouphael et al, 2004;Fallovo et al 2009a,b;Nicola et al, 2005;Coronel et al, 2009;Fontana and Nicola, 2009;Manzocco et al, 2011), since leafy vegetables such as lettuce and rocket tend to accumulate nitrates in their leaves in order to maintain high turgor pressure. Although lettuce is considered a nitrate accumulator and one of the major sources of nitrate intake in human diet (Di Gioia et al, 2013), the highest rate of N (200 mg L -1 ) implemented in the present study did not result in nitrate content higher than the limits allowed in E.U.…”

“…Due to a growing interest for baby vegetable products (lettuce, rocket, spinach and so forth), this technique is a useful means for producing premium products, since vegetables quality is severely affected by pre-and postharvest treatments (Rouphael et al, 2004). During the last years, vegetable production of processed and minimally processed products (fresh-cut products, mixed salads, baby products and so forth) in soilless culture techniques, including floating system, has gained significant interest Salerno et al, 2005;Nicola et al, 2005;Conesa et al, 2009;Fallovo et al, 2009a,b;Fontana and Nicola, 2009;Zanin et al, 2011;Klados and Tzortzakis, 2014).…”

“…Nicola et al (2005) reported that rocket plants grown in a soilless culture system had higher fresh leaf production in a shorter time period, compared to plants cultivated in soil, resulting in a higher total production of leaves. Moreover, Manzocco et al (2011) reported that lamb's lettuce plants grown hydroponically showed an increased yield and overall quality compared to soil-cultivated plants.…”

Production of rocket (Eruca sativa Mill.) on plug trays and on a floating system in relation to reduced nitrate content / Pridelava navadne rukvice (Eruca sativa Mill.) v gojitvenih ploščah in na plavajočem sistemu in možnosti redukcije vsebnosti nitrata

“…The technology is not new and has already been described by several authors (Fontana and Nicola, 2009). Nicola et al (2005) compared a traditional and soilless culture system with overhead irrigation to produce rocket. The soilless culture had about 75 % higher yield than rocket grown in local soil and peat.…”