Seasonal effects on production of radish and lamb's lettuce grown in a floating system

Because of the continuous increase of the fresh-cut market, it is crucial to identify the best methods to provide high productivity with an adequate global quality of raw material. From this standpoint, the floating system is very interesting. This experiment was meant to enhance the limited knowledge on lamb's lettuce (Valerianella locusta L. Latter) and radish (Raphanus sativus L. (Gr. Radicula)). The experiment was performed in a greenhouse during two growing seasons (spring and summer), adopting two plant densities (370 and 640 plants m-2 for radish, 1800 and 2400 plants m-2 for lamb's lettuce) and four nutrient solutions (differing in salinity by addition of 0, 10, 20 and 30 mmol L-1 of NaCl). For radish, the increase of plant density decreased marketable product. The total biomass and yield were negatively affected by the increase of salinity but average hypocotyl length and diameter were not. Furthermore, almost all the parameters showed higher values in spring cultivation. The growing season interacted mainly with plant density: while in spring the plant density did not affect the fresh weight, in summer this parameter was lower at the higher density. On the contrary, marketable yield was similar in spring while it was reduced at the higher density in summer. Yield of lamb's lettuce increased along with density while it was negatively affected by salinity. Quality traits such as chlorophyll content, leaf length and dry matter were improved at low density and higher salinity. In spring yield was higher than in summer but quality was poorer. The salinity plant density interacted with plant density and growing cycle on affecting leaf length with higher extent at D2 and in summer. Floating is a suitable cropping system for both lamb's lettuce and radish even if strong seasonal changes might occur in yield and quality of production.