New cultural techniques have been developed to satisfy market requirements and to produce healthy and sustainable food. The growing demand for baby leafy vegetables (BLV) encourages researchers to develop new production techniques. Floating system is a soilless culture system that allows growing plants at high densities reaching high yields in a short time. Moreover, it allows influencing nutritional status and composition of plants by modifying the nutrient solution (NS), by this system it is possible to control the final nitrate and oxalate contents, which are important safety aspect in BLV.

Italian and Spanish scientists led by Professor Silvana Nicola have published a review on the effects of 1) the nitrogen concentration and chemical form supplied to the growing plants and 2) the aeration level of the nutrient solution on the inherent quality of baby leafy vegetables. The review contains the major results from experiments conducted at the Università degli Studi di Torino and the Universidad Politécnica de Cartagena in the last 15 years.

Scientists tested floating system on different leafy species, such as rocket (Eruca sativa; Diplotaxis tenuifolia), lamb's lettuce (Valerianella olitoria), water and garden cress (Nasturtium officinalis; Lepidium sativum), lettuce (Lactuca sativa), purslane (Portulaca oleracea), spinach (Spinacia oleracea) and bladder campion (Silene vulgaris).

Silvana Nicola explains: "In these years we investigated the effects of concentrations from 4 to 16 mmol/L of nitrogen in the NS and of ratios between N-NO3- (nitrate nitrogen) and N-NH4+ (ammonia nitrogen) from 100 to 0%. In general, concentrations of 8-12 mmol/L of nitrogen used in the NS led to high yields and limited leaf nitrate accumulation, moreover the nitrogen provided at 40-60% of N-NH4+ form in the NS limited leaf nitrate accumulation. As regards the aeration levels of the NS, some species showed little sensitivity to oxygen depleted in the root medium, and were able to adapt to a gradual reduction in oxygen level. However, to increase yields, aeration is advisable, although the final quality of the product, in terms of functional phytochemicals concentrations, may be slightly lower. The level of oxygen had a different influence on the oxalate and nitrate contents depending on the studied species."

The full study is available online at:

Source: Silvana Nicola et al., 'Nitrogen and aeration levels of the nutrient solution in soilless cultivation systems as important growing conditions affecting inherent quality of baby leaf vegetables: a review', 2015, Acta Horticulturae, Vol. 1099, pages 167-177.

Silvana Nicola
Dept. DISAFA, VEGMAP, Università degli Studi di Torino
Via Leonardo da Vinci, 44
10095 Grugliasco (TO), Italy